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I. DEL: PREGLED HIDROLO[KIHRAZMER V LETU 2001

PART I: A REVIEW OF HYDROLOGICALCONDITIONS IN THE YEAR 2001

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A. POVR[INSKE VODE

VODOSTAJI IN PRETOKIREKIgor Strojan

V letu 2001 je po slovenskih rekah v ce-loti preteklo okoli deset odstotkov manj vode kotv dolgoletnem primerjalnem obdobju. Pretoki sepreko leta niso spreminjali skladno z ustaljenimipreto~nimi re‘imi rek. Obi~ajnih visokih voda vaprilu in v oktobru ni bilo.

Povpre~ni mese~ni pretoki rek so bili zredkimi izjemami, najve~ji januarja, marca terseptembra. V vseh ostalih mesecih so bili pov-pre~ni mese~ni pretoki manj{i od obdobnih (karta1 in graf 3). Izjema so bili pretoki na Muri, kjerso bila mese~na odstopanja pretokov od povpre~-ja veliko manj izrazita kot na ostalih slovenskihrekah.

Visokovodne konice so bile najve~jeve~inoma konec januarja. Ob tem so reke poplav-ljale ve~inoma obmo~ja 2- do 5-letnih poplav,izjemoma pa tudi obmo~ja 5-letnih poplav. Vi-sokim pretokom je botrovalo taljenje snega. Vsplo{nem se je vodnatost v tem ~asu zmanj{evalaod zahoda oz. severozahoda, kjer je bila najve~ja,proti vzhodu oz. severovzhodu, kjer je bilanajmanj{a.

Hidrolo{ke su{ne razmere leta 2001 sobile dokaj izrazite. Vodnatost rek se je pri~elazmanj{evati aprila, ko so bili mese~ni pretoki rek‘e nekoliko manj{i kot v dolgoletnem primerjal-nem obdobju. Pomanjkanje padavin je hidrolo{kesu{ne razmere postopno stopnjevalo vse do ju-lija in avgusta, ko so se neugodnim padavinskimrazmeram pridru‘ile visoke temperature zraka,ki so dodatno vplivale na izredno majhno vod-natost rek. Pretoki rek so bili med najmanj{imi vobdobju, dosegali so pet- in ve~letne povratnedobe malih pretokov (graf 3 in 4). Nekateremanj{e reke in potoki so za~asno presahnili. Pohidrolo{ko mokrem de‘evnem septembru so sepretoki ponovno zmanj{evali vse do konca leta.

Podrobneje so nizkovodne in visokovo-dne razmere v letu 2001 opisane v posebnih po-glavjih letopisa.

Dnevno spreminjanje pretokov na sloven-

A. SURFACE WATERS

WATER LEVEL AND RIVERDISCHARGEIgor Strojan

On the whole, river discharge in Slove-nia in the year 2001 was 10% lower than in themultiannual comparative period. During the year,the discharges did not change in accordance withthe stable discharge regimes of rivers. The usualhigh waters in April and October did not occur.

The mean monthly river discharges were,with rare exceptions, the highest in January,March and September. The mean monthly di-scharges in all other months were lower than thatof the period (Map 1 and Graph 3). An exceptionwas the Mura River where monthly deviationsfrom the mean discharge values were less evi-dent than on other Slovene rivers.

The yearly high water peaks were mainlyreached at the end of January. Rivers mainly flo-oded 2- to 5- year flooding areas, and exceptio-nally also 5- year flooding areas. Snow meltingwas the cause of high discharges. Generally, thequantity of water decreased from west or north-west, where it reached its peak, towards east ornorth-east, where it was lowest.

The dry period in 2001 was rather expli-cit. The quantity of water in rivers began to decre-ase in April when the monthly discharges of ri-vers were somewhat lower than in the comparati-ve period. The lack of precipitation gradually in-tensified the dry period, which lasted from July toAugust, when we registered high air temperaturesas well, which was an additional reason for theextremely low quantity of water in rivers. Riverdischarges were the lowest in this period, they re-ached 5 or more year return period of low dischar-ges (Graph 3 and 4). Some small rivers and stre-ams have temporarily run dry. After a hydrologi-cally wet September the discharges have starteddecreasing again up till the end of the year.

The low and high flows in 2001 are de-scribed in greater detail in the additional chap-ters of this yearbook.

Daily changes of discharges on Slovenerivers in 2001 are presented with mean daily di-

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skih rekah leta 2001 je predstavljeno s srednjimidnevnimi pretoki Save na vodomerni postaji vHrastniku (graf 4). Odstopanja od prikazanihpretokov so se tudi v letu 2001 pojavljala pred-vsem na rekah z druga~nim preto~nim re‘imom,od katerih je najbolj izrazit primer Mure, ki imasne‘ni preto~ni re‘im z obilnimi pretoki pom-ladi in poleti. V letu 2001 so na Muri velikomanj kot na drugih slovenskih rekah izstopalihidrolo{ko mokri meseci januar, marec in sep-tember.

Podrobnej{i pregled hidrolo{kih razmerprikazuje obdobje mesecev januarja, februarja inmarca kot hidrolo{ko zelo mokro. Pretoki so bilijanuarja in marca v povpre~ju dvakrat ve~ji kotnavadno v tem obdobju (graf 3), februar pa je bilpovpre~en. V prvih treh mesecih leta so bilenajbolj vodnate reke v severozahodni Sloveniji,kjer so bili mese~ni pretoki tudi trikrat ve~ji kotv primerjalnem obdobju. Pretok Mure je bil vtem ~asu le nekoliko ve~ji kot navadno. Januarjain marca, so se pretoki dvakrat mo~neje pove-~ali. Ob tem so reke tudi poplavljale.

Aprila, maja, junija, julija in avgusta so se

scharges of the Sava River on the gauging sta-tion in Hrastnik (Graph 4). Deviations from thedisplayed discharges have appeared in 2001mainly on rivers with different discharge regi-me, the most distinctive example being the MuraRiver, which has a snow discharge regime withhigh discharge in spring and summer. In 2001,the Mura River had an exceptionally hydrologi-cally wet January, March and September, howe-ver not as wet as other Slovene rivers.

A detailed review of hydrological condi-tions show the first three months (January, Fe-bruary and March) as hydrologically very wet.On average, the discharges were twice the nor-mal size in January and March (Graph 3), butthey reached average values in February. Riversin the north-west of Slovenia had the largest quan-tity of water in the first three months with mon-thly discharges three times higher in comparisonwith the comparative period. The Mura River di-scharge was a little higher than usual. In Januaryand March a substantial increase in the dischar-ges was noticed twice, which caused the riversto flood.

Karta 1: Razmerja med srednjimi letnimi pretoki leta 2001 in obdobja 1961-1990 ter grafi~ni prikazi razmerij med srednjimi mese~nimipretoki leta 2001 in obdobja 1961-1990. Vrednost razmerja 1 pomeni, da je bil pretok leta 2001 enak povpre~ju dolgoletnega obdobja.Map 1: The ratios between the mean annual discharges in 2001 and the period 1961-1990 along with graphic presentations of ratiosbetween mean annual discharges in 2001 and the period 1961-1990. Ratio value 1 means that discharge in 2001 was the same as theaverage multiannual mean.

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Graf 3: Razmerja med srednjimi mese~nimi pretoki v letu 2001 in obdobnimi srednjimi mese~nimi pretoki. Razmerja so izra~unana kotpovpre~ja razmerij na izbranih postajah (glej karto 1).Graph 3: The Ratios between the mean monthly discharges in the year 2001 and between the mean monthly discharges of the period.The ratios are calculated as mean values of ratios on selected stations (see Map 1).

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pretoki rek postopoma zmanj{evali. Hitrej{ezmanj{evanje pretokov so ob~asno prekinjale manj-{e padavine. Glede na primerjalne mesece v dolgo-letnem obdobju je preteklo po koritih rek aprila 10,maja in junija 40, julija 50 in avgusta 60 odstotkovmanj vode. Ob koncu su{nega obdobja so bile su{nerazmere najbolj izrazite, nekatere manj{e reke inpotoki so presahnili, najmanj{i pretoki so bili blizunajmanj{im pretokom iz dolgoletnega primerjal-nega obdobja.

V septembru so se pretoki mo~neje pove-~ali in kon~alo se je ve~mese~no poletno su{noobdobje. Druga~e od pri~akovanj so bile padavi-ne tudi po septembru manj izdatne kot navadnoin vodnatost rek se je ponovno zmanj{evala, to-krat vse do konca leta. V oktobru je bila vodna-tost 40 odstotkov, novembra 60 in v decembrucelo 70 odstotkov manj{a kot v primerljivih mese-cih dolgoletnega obdobja (graf 3). Zadnje decem-brske dni so bili pretoki nekaterih rek najmanj{iv letu (preglednica 1).

Podrobneje so hidrolo{ke razmere narekah v letu 2001 opisane v Mese~nih biltenihAgencije Republike Slovenije za okolje.

Primerjava zna~ilnih pretokov v letu2001 z zna~ilnimi pretoki v primerjalnem ob-

The river discharges have gradually de-creased in April, May, June, July and August. Afaster decrease of discharges was at times inter-rupted by smaller precipitation. With regard tothe comparative months there was 10% less wa-ter in rivers in April, 40% less in May and June,50% less in July and 60% less in August. Dryconditions were most explicit at the end of thedry period. Some small rivers and streams haverun dry and the smallest discharges were closeto the smallest values from the multiannual com-parative period.

The discharges have increased substan-tially in September and the dry period of severalmonths has ended. However, the precipitation wasless excessive than usual even after the wet Sep-tember and the water quantity has been decrea-sing until the end of the year. The water quantityin October was 40%, in November 60% and inDecember even 70% lower than in the compara-tive months of the multiannual period (Graph 3).The discharges of some rivers were lowest in thelast days of December (Table 1).

The hydrological conditions in 2001 aredescribed in greater detail in the Monthly Bulle-tin of the Environmental Agency of the Republicof Slovenia.

Graf 4: Srednji dnevni pretoki v letu 2001 in srednji mese~ni pretoki v dolgoletnem obdobju 1961 – 1990 na reki Savi v Hrastniku.Graph 4: Mean daily discharges in the year 2001 and mean monthly discharges in the multiannual period 1961 – 1990 on the Sava Riverin Hrastnik.

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Preglednica 1: Zna~ilni pretoki v letu 2001 in obdobju 1961–1990.Table 1: Characteristic discharges in the year 2001 and in the period 1961–1990.

Qnp .... najmanj{i pretok v letu – dnevno povp.nQnp ... najmanj{i mali pretok v obdobjusQnp ... srednji mali pretok v obdobjuvQnp ... najve~ji mali pretok v obdobjuQs ....... srednji pretok v letu – dnevno povpre~jenQs ..... najmanj{i srednji pretok v obdobjusQs ...... srednji pretok v obdobjuvQs ..... najve~ji srednji pretok v obdobjuQvk .... najve~ji pretok v letu – konicanQvk ... najmanj{i veliki pretok v obdobjusQvk ... srednje veliki pretok v obdobjuvQvk ... najve~ji veliki pretok v obdobju

Qnp .... minimum discharge in the year – daily averagenQnp ... minimum low discharge in the periodsQnp ... mean low discharge in the periodvQnp ... maximum low discharge in the periodQs ....... mean discharge in the year – daily averagenQs ..... minimum mean discharge in the periodsQs ...... mean discharge in the periodvQs ..... maximum mean discharge in the periodQvk .... maximum discharge in the year – peaknQvk ... minimum high discharge in the periodsQvk ... mean high discharge in the periodvQvk ... maximum high discharge in the period

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The comparison of characteristic di-scharges in 2001 with characteristic dischar-ges in the comparative period 1961-1990. TheMura and Sava rivers in the upper reach, the So~aRiver in Kobarid and the Savinja River in Velike[irje had the lowest discharge in December2001. The lowest discharge on the So~a River inSolkan was recorded at the end of October. Werecorded the lowest discharges on all other ri-vers in August. The lowest discharge of the Le-dava River in Polana, 5 l/s, was recorded as earlyas in July (Table 1 and Graph 5). The lowest di-scharges were on average 19% lower than in thecomparative period. The lowest discharges wererecorded in the north-east of Slovenia. The lowestdischarges were less significant in the north-west,where the quantity of water was the highest be-fore the summer drought.

Mean annual discharges of rivers pre-sented on Map 1, Graph 5 and Table 1 were onaverage 12 % lower than in the multiannual com-parative period. The discharges in the north-eastof Slovenia were among the lowest in the com-parative period (Table 1 and Graph 5). The meanannual discharge of the Mura River was 24 %lower than in the multiannual comparative pe-riod.

dobju 1961-1990. Mura, Sava v zgornjem toku,So~a v Kobaridu in Savinja v Velikem [irju soimele v letu 2001 najmanj{i pretok decembra.Najmanj{i pretok na So~i v Solkanu je bil konecoktobra. Na vseh ostalih rekah so bili pretokinajmanj{i avgusta. Na Ledavi v Polani je bilnajmanj{i pretok 5 l/s ‘e julija (preglednica 1 ingraf 5). V povpre~ju so bili najmanj{i pretoki 19odstotkov manj{i kot v primerjalnem obdobju.Pretoki so bili najmanj{i v severovzhodni Slove-niji. Na severozahodu, kjer je bila pred poletnosu{o vodnatost najve~ja, so bili najmanj{i preto-ki manj izraziti.

Srednji letni pretoki rek, ki so prikaza-ni na karti 1, grafu 5 in v preglednici 1, so bili vpovpre~ju 12 odstotkov manj{i kot v dolgoletnemprimerjalnem obdobju. Pretoki v severovzhodniSloveniji so bili med najmanj{imi v primerjal-nem obdobju (preglednica 1 in graf 5). Srednjiletni pretok Mure je bil 24 odstotkov manj{i kotv dolgoletnem primerjalnem obdobju.

V povpre~ju so bili najve~ji pretoki vletu 2001 16 odstotkov manj{i kot v dolgolet-nem obdobju. Nekoliko ve~ja kot navadno je bilavisokovodna konica na Vipavi v kraju Miren,ob~utno podpovpre~ne pa so bile visokovodne

Graf 5: Razmerja malih, srednjih in velikih pretokov v letu 2001 (po mesecih) ter razmerja karakteristi~nih pretokov obdobja 1961-1990. Vrednosti so podane relativno glede na srednje vrednosti malih, srednjih in velikih obdobnih pretokov.Graph 5: Ratios of low, medium and high discharges in the year 2001 (by months) and ratios of characteristic discharges in the period1961-1990. The values are relative, regarding the mean values of low, medium and high discharges of the period.

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The maximum discharges in 2001 wereon average 16% lower than in the multiannualperiod. The high-water peak in the Vipava Riverin Miren was somewhat higher than usual, thehigh-water peaks in the north-east of Slovenia andon the Mura River were substantially below ave-rage. The discharges were highest in January,which is a rarity if the comparative period is takeninto consideration. (Table 1 and Graph 5).

konice v severovzhodni Sloveniji ter na Muri.Pretoki so bili v veliki ve~ini najve~ji januarja,kar je glede na primerjalno obdobje redkost (pre-glednica 1 in graf 5).

Struga Kobiljskega potoka je bila pri vodomerni postaji Kobilje suha ves avgust (foto: Peter Frantar, 30. avgust 2001).The riverbed of the water course Kobiljski potok at the gauging station was dry whole August (photo: Peter Frantar, August 30, 2001).

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TEMPERATURE REKIN JEZERIgor Strojan

Leta 2001 so bile temperature Mure,Save, Kamni{ke Bistrice, Ljubljanice, Krke inSo~e ter Blejskega in Bohinjskega jezera pov-pre~no nekaj manj kot pol stopinje Celzija (°C)vi{je kot v ve~letnem primerjalnem obdobju.Predvsem so bile nadpovpre~ne temperature ja-nuarja in februarja. Nekoliko vi{je kot navadnoso bile temperature voda tudi v su{nem obdobjuleta, julija in avgusta. Ob~utna je bila ohladitevvoda v za~etku septembra in v decembru.

Leto 2001 se je pri~elo z ob~utno vi{jimitemperaturami voda kot navadno. Januarja in feb-ruarja so imele vode povpre~no temperaturo 6 °C,kar je za reke 1,9 °C in za jezera 1,5 °C ve~ kot vprimerjalnem obdobju. Naslednja dva meseca sose temperature voda pribli‘ale povpre~nim ob-dobnim vrednostim, v maju pa so bile vode zo-pet toplej{e kot so navadno v tem mesecu. V na-jbolj su{nem obdobju leta, v juliju in avgustu, soimele reke povpre~no temperaturo 17,3 °C, jezerapa 18,6 °C, kar je 0,4 °C oz. 0,8 °C ve~ kot vve~letnem primerjalnem obdobju. Septembra paso se temperature voda izrazito zni‘ale. Ohladileso se za 1,3 °C pod povpre~no obdobno septembr-sko vrednost. Oktobra so bile vode zopet nadpov-pre~no tople. November je bil temperaturno

TEMPERATURES OF RIVERSAND LAKESIgor Strojan

The temperatures of the Mura, Sava,Kamni{ka Bistrica, Ljubljanica, Krka and So~arivers as well as lakes Bled and Bohinj in 2001were on average less than half a degree (°C) hi-gher than in the multiannual comparative period.January and February had high temperatures,which were above average. Water temperaturesin the dry season of the year (July and August)were somewhat higher than usual. There was aconsiderable cooling of water at the beginningof September and December.

The temperatures at the beginning of 2001were considerably higher than usual. The meanwater temperature in January and February was6 °C which is 1.9 °C higher for rivers and 1.5 °Cfor lakes when compared to the comparative pe-riod. In the next two months the temperatureswere close to the mean values of the period, butthe waters were warmer again in May as it isusually the case. The mean temperature in thedriest period of the year (July and August) was atrivers 17.3 °C and lakes 18.6 °C. That was 0.4 °Cand 0.8 °C higher than in multiannual compara-tive period. However, in September the water tem-perature dropped considerably. The water was1.3 °C below the mean September value of the

Graf 6: Temperaturna nihanja slovenskih rek Mure, Save, Kamni{ke Bistrice, Ljubljanice, Krke in So~e leta 2001 (po mesecih).Graph 6: Temperature fluctuations of the Mura, Sava, Kamni{ka Bistrica, Ljubljanica, Krka and So~a rivers in 2001 (by months).

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podoben obdobnemu povpre~ju, decembra pa sobile vode najbolj hladne v letu, temperature vodeso bile podpovpre~ne (graf 8).

V izbranih primerih poteka temperaturnihnihanj na rekah na grafu 6 izstopata reka Krka(vodomerna postaja Podbo~je) kot najtoplej{a inKamni{ka Bistrica (vodomerna postaja Kamnik)kot najbolj hladna reka. Razvidne so relativnovisoke temperature voda januarja in februarja ternajni‘je temperature decembra. Povi{anim maj-skim temperaturam sledi zni‘anje temperaturjunija, nato pa povi{anje temperatur v su{nemobdobju julija in avgusta. Zelo izrazito je zni‘anjetemperatur septembra.

V Blejskem in Bohinjskem jezeru je bilpotek temperaturnih sprememb podoben kot narekah, le da sta se jezeri pri~eli bolj izrazito ogre-vati nekoliko kasneje kot reke (graf 7). Manj{atemperaturna nihanja so na obeh jezerih ve~inomamanj izrazita kot na rekah. Bohinjsko jezero jebilo kot obi~ajno vse leto hladnej{e kot Blejsko, vpovpre~ju celega leta za 3,4 stopinje Celzija.

Primerjava zna~ilnih temperatur vodaz ve~letnim obdobjem. Reke in obe jezeri sobili najbolj hladni ob koncu leta. To je bilo izrazitoodstopanje od obi~ajnega temperaturnega re‘imavoda, saj so vode obi~ajno najbolj hladne janu-arja ali februarja. Najni‘je temperature re~nihvoda v letu 2001 so bile ve~inoma nekoliko ni‘je

period. The temperature of water in October wasabove average. November was similar to the va-lue of the period as far as temperature is concern-ed, but December saw the lowest temperaturesof the year (Graph 8).

In the chosen examples of temperaturefluctuations in rivers (Graph 6), the followingrivers stand out: the Krka River (gauging stationPodbo~je) as the warmest river and the Kamni{kaBistrica River (gauging station Kamnik) as thecoldest river. Obvious are the relatively highwater temperatures in January and February andthe lowest temperatures in December. High tem-peratures in May are followed by a decrease intemperature in June and by an increase in thedry period of July and August. The decrease intemperature is extremely evident in September.

The temperature change in Lake Bled andLake Bohinj was similar to that of the rivers.However, the temperature of both lakes has star-ted to increase a little later (Graph 7). Minor tem-perature fluctuations in both lakes were less no-ticeable than in rivers. Lake Bohinj was colderthan Lake Bled throughout the year as it is usuallythe case, by 3.4 °C on yearly average.

Comparison of characteristic watertemperatures in the multiannual period. Therivers and both lakes were the coldest at the endof the year. This was a marked deviation from

Graf 7: Temperaturna nihanja Blejskega in Bohinjskega jezera leta 2001 (po mesecih).Graph 7: Temperature fluctuations of Lake Bled and Lake Bohinj in 2001 (by months).

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kot v primerjalnem obdobju. Najni‘ji tempera-turi obeh jezer, 4,6 °C Blejskega in 3 °C Bohin-jskega jezera, ki sta navadno najbolj hladni v dru-gi polovici zime, sta bili okoli 2 °C vi{ji od pov-pre~ja.

Srednje temperature izbranih rek in obehjezer so bile 0,4 °C vi{je od povpre~ja. Srednjaletna temperatura rek na izbranih postajah je bila10,4 °C, jezer pa 12,1 °C. Srednje mese~ne tem-perature so bile glede na primerjalno obdobje naj-vi{je januarja, februarja in oktobra, najni‘je paseptembra in decembra (graf 8).

Najvi{je temperature rek in obeh jezer sobile v splo{nem nadpovpre~ne. Vode so bile naj-bolj tople avgusta. ^etrtega avgusta je izstopalatemperatura Krke v Podbo~ju s 24,8 °C. Le dvedesetinki stopinje hladnej{e je bilo Blejsko jeze-ro 3. avgusta.

the usual temperature regime of water, since wa-ters reach the lowest temperature in January andFebruary. The lowest temperature of river wa-ters in 2001 was predominantly lower than in thecomparative period. The lowest temperature ofboth lakes, Lake Bled 4.6 °C and Lake Bohinj3 °C which are usually coldest in the second halfof winter, were around 2 °C higher than average.

Mean temperatures of chosen rivers andboth lakes were 0.4 °C higher than average. Incomparison with the comparative period, themean yearly river temperature on chosen stationswas 10.4 °C, and lake temperature was 12.1 °C.Mean monthly temperatures were highest in Ja-nuary, February and October and lowest in Sep-tember and December (Graph 8).

The highest temperatures of rivers andboth lakes were generally average. The waterswere warmest in August. On August 4 the tem-perature of the Krka River in Podbo~je stood outwith its 24.8 °C. Lake Bled was only two-tenthsof a degree colder on August 3.

Graf 8: Odstopanja srednjih mese~nih temperatur v letu 2001 od srednjih mese~nih temperatur obdobja na izbranih rekah in jezerih.Odstopanja so izra~unana kot povpre~ja odstopanj na {estih re~nih in dveh jezerskih merilnih postajah (glej graf 6 in 7).Graph 8: Temperature deviations of mean monthly temperatures from the monthly temperatures on chosen rivers and both lakes in theyear 2001. The deviations are calculated as mean values of deviations on six water gauge stations on the rivers and on two stations on thelakes (see Graphs 6 and 7).

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VSEBNOST SUSPENDIRANEGAMATERIALA V REKAHFlorjana Ulaga

Hitrost preme{~anja plavin, koli~ina suspendi-rane snovi, velikost zrn, mineralo{ka sestava,vsebnost mikroorganizmov in motnost vode soosnovni parametri za ugotavljanje lastnosti rekez vidika kalnosti. Material, ki zaradi spiranja pre-perine ali erodiranja bre‘in v povirju, lahko patudi kot posledica umetnih vplivov v bli‘ini stru-ge, potuje po reki, znatno pripomore k njenemuspreminjanju. Delci se dolvodno ob zmanj{anitransportni sposobnosti reke usedajo na re~nodno. Posledice dinamike preme{~anja snovi sospremembe v in ob re~ni strugi, zapolnjevanjevodnih zadr‘evalnikov, zablatenje re~nega dnazaradi usedanja drobnih zrn in s tem povezanespremembe v vodnem krogu, predvsem pri po-vezavi povr{inskih in podzemnih voda.

Preme{~anje trdnih delcev v strugi. Vceloti pod vplivom turbulence preme{~en re~nimaterial imenujemo re~ni nanos. Glede na ve-likost delcev in hitrost prenosa ga delimo nalebde~e plavine v celotnem re~nem prerezu vsuspendirani obliki in na prod, ki se premika pore~nem dnu s kotaljenjem. Med tema dvemaoblikama ni ostre meje. Isto~asno, ko se premi-kajo drobni delci v vodi, se po re~nem dnu valijove~ji delci oz. prodniki. S pove~anjem hitrostivode prehaja material z re~nega dna v suspenz, stem se pove~uje koli~ina lebde~ega nanosa. Obvisokovodnih stanjih je tudi vsebnost suspendi-ranega materiala mo~no pove~ana. Splo{no zna-no je dejstvo, da usedlina izhaja iz povirja reke,se po reki prena{a in na koncu odlaga. Zato lahkogovorimo o treh obmo~jih re~nega sistema. Zvidika hitrosti prenosa usedline je tako najboljzanimiv osrednji del reke, z vidika celotnega pre-nosa materiala na dolo~enem pore~ju pa je boljpomembno poznavanje geolo{kih in hidrolo{kihzna~ilnosti povirnega obmo~ja ter dejanskakoli~ina odlo‘enega materiala v spodnjem delureke.

Mre‘a postaj monitoringa suspendira-nega materiala. Cilj spremljanja je izra~un skup-ne koli~ine materiala, ki se premesti prek izbra-nega mesta v vodotoku v dolo~eni ~asovni enoti.Dinamiki gibanja plavin v vodi sledimo z mer-jenjem vsebnosti suspendiranega materiala, izkatere pri izmerjenem pretoku izra~unamo pre-nos materiala. Pogostost odvzema vzorcev je

THE CONCENTRATIONOF SUSPENDED MATERIALIN RIVERSFlorjana Ulaga

The speed of solids transporting, the amount ofsuspended material, the size of particles, mine-ralogical structure, the content of microorgani-sms and water opacity are the basic parametersin establishing river characteristics regarding tur-bidity. The material which travels down the rivercan contribute to its changing due to the washingdown of weathered debris or eroding of riverbanks in headwaters or as a consequence of out-side interference in the vicinity of river channels.With a diminished transporting capacity of theriver the particles can then sink downstream tothe river bottom. The consequences of transportdynamics are the changes in and by the riverchannel, the filling of water reservoirs, muddingthe river bottom because of small particlessinking and corresponding changes in the watercycle, mainly in connection of surface waters andgroundwaters.

Transport of solid particles in the riverchannel. The river material wholly transportedunder the influence of turbulence is called riveralluvium. According to the size of particles wedivide it into floating solids (found in the wholeof the river cross section in suspended form) andinto gravel, which moves along the bottom of theriver. There is no great distinction between the two.At the same time, when the small particles movein water, bigger particles or pebbles move alongthe bottom of the river. When the speed of the waterincreases the material proceeds from the riverbottom to the sediments and the amount of floa-ting material increases. High-water situations cau-se a substantial increase in the concentration ofsuspended material. It is a common fact that thesediments come from the headwaters of the river,are transported through the river and finally depo-sited in the river. Therefore, we can speak of threeareas of the river system. If taking into considera-tion the speed of the sediment transfer, the mostinteresting part of the river is the middle part. Ne-vertheless, if taking the whole material transfer inthe specific area into consideration, it is the know-ledge of geological and hydrological characteri-stics of the headwater area and the actual quantityof deposited material in the lower part of the riverthat is essential.

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odvisna od zna~ilnosti prispevnega obmo~ja inod preto~nega re‘ima. Dosedanje analize suspen-diranega materiala so pokazale, da se pribli‘no70 odstotkov celotnega materiala premesti obvisokovodnih dogodkih. Zaradi tega je potrebnopogosto vzor~enje v ~asu visokih valov.

Redna merjenja vsebnosti suspendirane-ga materiala izvajamo na {tirih vodomernih po-stajah: na Muri v Gornji Radgoni, na Savi v Hra-stniku, na Savinji v Velikem [irju in na Vipavi vMirnu. Enkrat dnevno se odvzame vzorec s pro-stornino enega litra, ki ga analiziramo v labora-toriju po klasi~ni filtracijski metodi. Rezultatianaliz so izmerjene vsebnosti suspendiranegamateriala (c), izra‘ene v g/m3 vode. Ob tem senekajkrat letno opravljajo tudi profilne meritvesuspendiranega materiala: vzorci se odvzamejov posameznih to~kah pre~nega prereza. Na pod-lagi vsebnosti snovi v odvzetih vzorcih izra~u-namo srednjo vsebnost v prerezu, s pomo~jo iz-merjenega pretoka pa tudi trenutni prenos suspen-dirane snovi.

Poleg rednega odvzema in analiziranjavzorcev poteka tudi odvzem vzorcev ob izred-nih hidrolo{kih razmerah na devetih vodomer-nih postajah. S pomo~jo analiz teh vzorcev do-

The monitoring network for suspendedmaterial. The aim of monitoring is the calcula-tion of the total quantity of material, transportedthrough a chosen place in the stream in a speci-fic time unit. The dynamics of solids movementin water can be traced by measuring the concen-tration of suspended material. When the measu-red discharge value is gained, we can calculatethe transfer of the material. The frequency of sam-ples taking depends on the characteristics of thearea in question and on the discharge regime. Theanalyses of the suspended material made so far,showed that approximately 70% of the entirematerial is transferred during high water occur-rences. Thus, frequent sampling during highwaves is necessary.

Regular measurements of suspendedmaterial are carried out on four gauging stations:on the Mura River in Gornja Radgona, on theSava River in Hrastnik, on the Savinja River inVeliko [irje and on the Vipava River in Miren.Once a day, a 1 litre sample is taken and analy-sed in a laboratory according to the classical fil-tration method. The results are the measured con-centrations of suspended material (c) in g/m3 ofwater. Several times a year profile measuremen-

Vzor~evanje z batometrom (foto: Toma` Haller).Suspended material water sampling (photo: Toma` Haller).

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polnilne mre‘e la‘je in pravilneje vrednotimopodatke rednih meritev, hkrati pa rezultati pred-stavljajo pregled stanja ob visokovodnih razme-rah po vsej Sloveniji. Izredni odvzemi vzorcevso bili leta 2001 na [~avnici v Pristavi, na Pesni-ci v Zamu{anih, na Me‘i v Oti{kem Vrhu, naDravinji v Vidmu, na Sotli v Rakovcu, na So~i v

ts of suspended material are performed as well:the samples are taken at individual points of asectional view. On the basis of substance con-centration in the samples the mean concentra-tion in the cross section is calculated. By usingthe discharges measurements, a momentary tran-sfer of suspended material is calculated.

Karta 2: Postaje z rednim in izrednim odvzemom vzorca v letu 2001.Map 2: Stations with every day and occasionally sampling in 2001.

Kobaridu, na Idrijci v Hote{ku, na Ba~i v Ba~ipri Modreju in na Reki v Cerkvenikovem mlinu.

Mre‘a postaj za spremljanje vsebnostisuspendiranega materiala se je v Sloveniji zelospreminjala. Za~etki segajo v leto 1955, ko sopri~eli z odvzemanjem vzorcev v pore~ju Savinje.Redno spremljanje vsebnosti suspendiranegamateriala na rekah Mura in Vipava poteka od leta1985. Odvzemna mesta na Savi pa se spre-minjajo.

Rezultati meritev vsebnosti suspendi-ranega materiala v letu 2001. Ob pregledu iz-merjenih vsebnosti suspendiranega materiala napostajah z dnevnim odvzemom vzorcev ugoto-vimo, da leto 2001 ni bilo izjemno glede koli~inedrobnih delcev v vodi, pa~ pa bolj glede ~asanastopa pove~anih vsebnosti. Za sne‘ni preto~nire‘im, kakr{nega ima reka Mura, je zna~ilen

Along with regular taking and analysingof samples, a sample taking in exceptional hydro-logical situations on nine gauging stations takesplace. With the help of sample analysis of thesupplementary network, the data of regular mea-surements are easier and more accurately eva-luated and at the same time the results present anoverview of the high-water condition all overSlovenia. Exceptional sample takings took placein 2001 on the [~avnica River in Pristava, on thePesnica River in Zamu{ani, on the Me‘a Riverin Oti{ki Vrh, on the Dravinja River in Videm,on the Sotla River in Rakovec, on the So~a Riverin Kobarid, on the Idrijca River in Hote{ek, onthe Ba~a River in Ba~a near Modrej on the RekaRiver in Cerkvenikov mlin (mill).

The network of stations for monitoringthe concentration of suspended material has been

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preto~ni vi{ek ob prehodu pomladi v poletje, to-rej maja. Obdobna najvi{ja vsebnost suspendi-ranega materiala je bila prav tako izmerjena vmaju leta 1996, ko je kar 43-krat presegla sred-njo obdobno vsebnost v Muri. V letu 2001 jevi{ek nastopil ‘e januarja, kar lahko pripi{emoizrednim vremenskim razmeram in obilnim pa-davinam v vodozbirnem zaledju vodomerne po-staje Gornja Radgona. Najve~je letne vsebnostismo izmerili januarja tudi v Savinji in Vipavi,~eprav bi jih glede na de‘no-sne‘ni preto~nire‘im, za katerega je zna~ilen preto~ni vi{ek pom-ladi in jeseni, pri~akovali kasneje. Prav tako januarjasmo izmerili najve~jo vsebnost suspendiranegamateriala v Savi. Vzorec, ki je bil odvzet 26. ja-nuarja 2001 v Hrastniku, je vseboval 610 g/m3 su-spenza. Rezultat hkrati predstavlja najvi{jo vseb-nost izmerjeno na tem mestu od leta 1998 dalje.

Analiza vzorcev, odvzetih ob izrednihhidrolo{kih razmerah, odra‘a hidrolo{ko suholeto 2001. Vsebnosti suspendiranega materialanikjer, z izjemo Dravinje, niso bile velike gledana dolgoletna spremljanja. Analiza vzorcaodvzetega v Dravinji je prikazala izredno ve-like vsebnosti suspendiranega materiala, saj jete‘a drobnih zrnc v vodi presegla 4,5 kg/m3.Ve~je vsebnosti smo v preteklih 17-ih letihspremljanja izmerili le {e v Pesnici leta 1997, vDravinji 1999 in v Savinji ter So~i novembra2000.

Prenos suspendiranega materiala. Od-nos med spreminjanjem pretoka in vsebnostjo su-spendiranega materiala v dolo~enem ~asu ni po-vsem linearen. Najve~ja vsebnost suspenza v vodinastopi pogosto nekoliko pred vi{kom visoko-vodnega vala. Zato je tudi predvidevanje koli~insuspenza zelo te‘avno. Upo{tevati je potrebno, vkaterem delu vodozbirnega zaledja so bile pada-

changing in Slovenia. The beginnings date backto 1955, when we started with the sample takingin the catchment area of the Savinja River. A re-gular monitoring of suspended material concen-tration on the Mura and Vipava rivers has beentaking place since 1985. The sampling points onthe Sava River are changing.

The results of the suspended materialconcentration measurements in 2001. By exa-mining the measured concentrations of suspen-ded material on stations where daily sampletaking is carried out, it can be seen that 2001 wasnot an exceptional year as regards the quantityof small particles in the water, but it was excep-tional because of the time of the increased con-centration of material. A discharge surplus, cha-racteristic of the snow discharge regime (theMura River), occurs in the transition from springto summer, i.e. in May. The highest concentra-tion of suspended material of the period wasmeasured in May 1996 and it exceeded the meanconcentration of the period by 43 times. In 2001,the culmination was reached already in January,which can be ascribed to exceptional weatherconditions and abundant precipitation in water-collecting hinterland of gauging station GornjaRadgona. The highest yearly concentrations weremeasured in January in the Savinja and Vipavarivers, although we would expect them to appearlater according to the rain-snow discharge regi-me, a characteristic of which is a discharge peakin spring and autumn. The highest concentrationof suspended material in the Sava River wasmeasured in January as well. The sample takenon January 26 in Hrastnik contained 610 g/m3 ofsediment. This result presents the highest mea-sured concentration in this place since 1998.

Preglednica 2: Najve~je vsebnosti suspendiranega materiala vzorcev postaj z enkrat dnevnim odvzemom v letu 2001 in v obdobju1985–2000.Table 2: The highest concentration of suspended material in samples with one daily taking in 2001 and in the period 1985–2000.

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vine, kak{na je geolo{ka zgradba obmo~ja, pred-hodna namo~enost tal pa tudi ~as od zadnjegavisokovodnega vala.

Zmno‘ek vsebnosti suspendiranega ma-teriala in pretoka vode skozi re~ni prerez je pre-nos suspendiranega materiala S (kg/s). Ta poda-tek je tudi cilj vsakodnevnega odvzema vzorcev,laboratorijskih analiz in neprekinjenih spremljanjpretokov v izbranih re~nih prerezih. Iz pregled-nice 4 so razvidne razlike med letnimi vrednost-mi prene{ene snovi. Na podlagi poznavanja veli-kosti pore~ja lahko ocenimo zni‘evanje zemelj-skega povr{ja v zaledju posamezne postaje. Takolahko ocenimo, da bi se ob podobnih hidrolo{kihin erozijskih razmerah, kot smo jih zabele‘ili v10-letnem obdobju, povr{je pore~ja Mure v tiso-~ih letih zni‘alo za 12 mm, Vipave za 16 mm,Savinje pa za 106 mm. Pri interpretaciji teh vred-osti pa ne smemo pozabiti na dejstvo o geolo{kiraznolikosti zaledja, na selektivnost erozije, nakorozijo na kra{kih obmo~jih ter na kratek nizpodatkov in dolgo dobo, ki je potrebna za ve~inogeomorfolo{kih sprememb.

The analysis of the samples taken inexceptional hydrological conditions reflects ahydrologically dry year 2001. The concentrationof suspended material was never high (with theexception of the Dravinja River) according to themany years of monitoring. The analysis of thesample taken in the Dravinja River showed excep-tional high concentrations of suspended material,since the weight of the particles exceeded 4.5 kg/m3. Such concentrations were measured only inthe Pesnica River in 1997 (in the 17 years ofmonitoring), in the Dravinja River in 1999 andin the Savinja River and in the So~a River inNovember 2000.

The transfer of suspended material.The relation between the discharge change andthe concentration of suspended material in a spe-cific time is not entirely linear. The highest con-centration of sediment frequently appears justbefore the peak of the high-water wave. Hence,it is difficult to foresee the quantity of sediment.The part of catchmentwhere the precipitationoccurs has to be taken into consideration as wellas the geological structure of the area, previousground wetness and the time passed since the lasthigh-water wave.

The product of the concentrations of su-spended material and water discharge through

Preglednica 3: Najve~je vsebnosti suspendiranega materiala vzorcev odvzetih ob izrednih hidrolo{kih razmerah.Table 3: The highest concentration of suspended material in samples taken in exceptional hydrological conditions.

Preglednica 4: Letne vrednosti prenesenega suspendiranega materiala (tiso~ ton).Table 4: Yearly values of transported suspended material (thousand tons).

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cross section equals to the transfer of suspendedmaterial S (kg/s). The data acquired is the aim ofthe daily sample taking, laboratory analysis andconstant discharge monitoring in chosen rivercross sections. Table 4 shows the differencesbetween yearly values of transferred substances.On the basis of the catchment area knowledge,the decrease of earth surface in the hinterland ofindividual stations can be estimated. In this way,the following estimate is possible: in similarhydrological and erosion conditions as were re-gistered in the 10-year period, the surface of theMura River catchment area would erode for 12mm, the catchment area of the Vipava River for16 mm and the catchment area of the SavinjaRiver for 106 mm. When interpreting these va-lues we must not forget the geological variety ofthecatchment, the selectivity of erosion, the cor-rosion in karstic areas, the short set of data andthe long period necessary for most of the geo-morphologic changes.

Odvzem vzorcev (foto: Florjana Ulaga).Water sampling (photo: Florjana Ulaga).

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NIZKE VODE IN HIDROLO[KASU[AMira Kobold

V letu 2001 so bili srednji mese~ni pre-toki v prvi tretjini leta pove~ini v mejah srednjihobdobnih mese~nih pretokov (sQs), potem pa vsedo konca leta, z izjemo septembra, pod srednji-mi obdobnimi mese~nimi pretoki, v mejah sred-njih malih pretokov (sQnp). Najmanj{i mese~nipretoki so bili v prvi polovici leta v mejah sre-dnjih malih obdobnih pretokov, v drugi polovicileta pa pod srednjimi malimi pretoki. V poletnihmesecih so se ponekod pribli‘ali najmanj{im iz-merjenim obdobnim pretokom (nQnp), vendarnajmanj{i obdobni pretoki v letu 2001 niso bilidose‘eni (graf 9). Nizkovodno stanje je povzro-~ila majhna koli~ina padavin. V januarju, marcuin septembru je bila zlasti v zahodni in osrednjiSloveniji znatno ve~ja od obdobnih mese~nih

LOW FLOWS ANDHYDROLOGICAL DROUGHTMira Kobold

The mean monthly discharges in the firstthird of 2001 were mainly within the limits ofmean monthly discharges of the period (sQs).Afterwards, until the end of the year (with theexception of September), the mean monthly di-scharges were below the mean monthly dischar-ges of the period and within the limits of meanlow discharges (sQnp). The lowest monthly di-scharges were within the limits of mean low di-scharges of the period in the first half of the year.In the second half of the year, they were belowthe mean low discharges. In some places in sum-mer they approached the lowest measured di-scharges of the period (nQnp), however the lowestdischarges of the period in 2001 were not rea-ched (Graph 9). The low flows were caused by

Graf 9: Srednji in minimalni mese~ni pretoki v letu 2001, mese~na koli~ina padavin ter obdobne mese~ne vrednosti.Graph 9: Mean and minimal monthly discharges in 2001, monthly quantity of precipitation and monthly values of the period.

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vrednosti, v ostalih mesecih pa je bila v mejahsrednjih obdobnih mese~nih vrednosti ali manj{a.Koli~ina padavin, ki je bila najni‘ja v severovzhod-ni Sloveniji, je povzro~ila hidrolo{ko su{o v temdelu dr‘ave ‘e v prvi tretjini leta.

Nizkovodno stanje smo v ve~jem deludr‘ave za~eli bele‘iti v maju, ko so se pretokirek po dr‘avi zmanj{ali pod srednje pretoke indosegli vrednosti srednjih malih pretokov. V ju-niju so bili prehodi vremenskih front dokaj enako-merno porazdeljeni. Zaradi tega so bili pretokive~ine rek v juniju v mejah srednjih obdobnihpretokov. [ele proti koncu meseca, ko se je usta-lilo lepo vreme, so se pretoki rek ponekod pri-bli‘ali srednjim malim obdobnim junijskim pre-tokom.

Hidrolo{ka su{a se je pri~ela v juliju inse nadaljevala v avgustu, ko so bili na ve~ini rekdose‘eni najni‘ji pretoki v letu 2001. Julij in av-gust sta bila najbolj suha meseca v letu. Z izjemoPoso~ja je koli~ina padavin v teh dveh mesecihdosegla le od 30% do 50% padavin povpre~ja1971-2000. Padavine v juliju so bile prostorskoneenakomerno razporejene. Julijska temperatu-ra zraka je bila nad dolgoletnim povpre~jem.Povpre~na dnevna temperatura zraka v Ljublja-ni je v juliju zna{ala 21,9 °C in je bila za 2 °Cnad povpre~jem primerjalnega obdobja. Prvipojavi hidrolo{ke su{e segajo v drugo polovicojulija, ko so bili pretoki v mejah srednjih malihobdobnih pretokov za mesec julij. Tudi na Muri,ki ima sne‘ni re‘im in je obi~ajno najbolj vod-nata v poletnih mesecih, smo od junija naprejbele‘ili male pretoke. Izjema je bila le So~a vzgornjem toku, kjer smo v juliju {e bele‘ili sred-nje pretoke. Vodnatost rek se je zaradi pogostihneviht v juliju prostorsko in ~asovno neenako-merno zmanj{evala. Ob koncu julija pa so se vre-menske razmere ustalile in takrat smo ‘e bele‘iliizrazito zmanj{evanje pretokov. Relativno naj-manj{i pretoki so bili zabele‘eni na rekah v osred-nji Sloveniji (Grada{~ici, Ljubljanici, Savinji vspodnjem toku), na Primorskem ter v vzhodni inseverovzhodni Sloveniji. Najmanj{i pretoki nisodosegli najmanj{ih malih julijskih obdobnih pre-tokov. Na ve~ini opazovanih rek v juliju pretokiniso presegli vrednosti dveletne povratne dobemalih pretokov.

Avgustovska koli~ina padavin je bilamanj{a od julijske in precej pod dolgoletnim pov-pre~jem. Pretoki rek so se vseskozi zmanj{evaliin so padli pod srednje obdobne male pretoke ter

small quantity of precipitation. Especially in thewestern and the central part of Slovenia it wasconsiderably higher than the monthly values ofthe period in January, March and September.During the rest of the months it was within thelimits of mean monthly values of the period orlower. The quantity of precipitation, which waslowest in the north-east of Slovenia, causedhydrological drought in the first third of the yearin this part of the country.

Low flows were recorded in most partsof the country in May, when river dischargesacross the country decreased below mean dischar-ges and reached the values of mean low dischar-ges. The cold fronts were evenly distributed inJune. Thus, the discharges of most of the riversin June were within the limits of mean dischar-ges of the season. It was not until the end of themonth when the weather stabilized that the di-scharges approached mean low discharges forJune.

Hydrological drought occurred in Julyand continued in August, when most of the ri-vers reached the lowest discharges in 2001. Julyand August were the driest months of the year.With the exception of the Poso~je region, theamount of precipitation in these two months rea-ched only 30% to 50% of the yearly precipita-tion average in 1971-2000. The precipitation inJuly was spatially unequally distributed. The airtemperature in July was above the multiannualmean. The mean daily air temperature in Lju-bljana in July was 21.9 °C, which was 2 °C abo-ve the average of the comparative period. Firstoccurrences of hydrological drought were recor-ded in the second half of July, when the dischar-ges were within the limits of mean low dischar-ges for July. Even on the Mura River with itsnival regime and usually the greatest quantity ofwater in summer months, we have recorded lowdischarges from June onwards. The So~a Riverin the upper reach was the only exception, wheremean discharges were still recorded in July. Thequantity of water in July was spatially as well astemporally unevenly decreasing due to frequentstorms. At the end of July, the weather condi-tions became stable again and the dischargesbegan decreasing rapidly. Relatively low dischar-ges were recorded on rivers in central Slovenia(in lower reaches of the Grada{~ica, Ljubljanicaand Savinja rivers), in Primorska region, No-tranjska region, in the east and north-east of

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se proti koncu avgusta pribli‘ali najmanj{im av-gustovskim obdobnim pretokom. Relativno naj-manj{i pretoki so bili zabele‘eni na manj{ih rekahv osrednji in ju‘ni Sloveniji, na notranjsko kra{-kem obmo~ju, na Primorskem, {ir{em obmo~juDravskega polja, v Slovenskih Goricah in Prek-murju. Najve~jo vodnatost rek smo bele‘ili napovirnih delih alpskih rek (So~a). Pretoki so nave~ini opazovanih rek dosegli vrednosti dve- dopet-letne povratne dobe malih pretokov. Na Ljub-ljanici, Savinji v spodnjem toku, Ri‘ani, Sotli inLedavi so bili izmerjeni mali pretoki s pet- do de-set-letno povratno dobo, na Pesnici in Kolpi pamali pretoki z deset- do dvajset-letno povratno

Slovenia. The lowest discharges did not reach thelowest low discharges for July. The dischargeson most of the observed rivers in July did notexceed the 2-year return period for low dischar-ges.

The amount of precipitation in Augustwas lower than in July and considerably belowthe multiannual mean. The river discharges wereconstantly decreasing and fell below mean lowdischarges of the period. Towards the end ofAugust they approached the lowest dischargesfor August. Relatively lowest discharges wererecorded on small rivers in central and southernSlovenia, in the areas of Notranjska and Kras,

Graf 10: Srednji dnevni pretoki (Qs) za obdobje od maja do konca decembra 2001 in obdobni mese~ni pretoki (sQs, sQnp, nQnp).Graph 10: Mean daily discharges (Qs) for the period from May to the end of December 2001 and periodical monthly discharges (sQs,sQnp and nQnp).

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the Primorska region, a greater area of the DravaPlain, Slovenske gorice and the Prekmurje re-gion. The highest water levels were recorded inthe headwaters of Alpine rivers (the So~a River).The discharges on most of the observed riversreached 2- to 5-year return period values of lowdischarges. Low discharges with 5- to 10-yearreturn period were measured on the LjubljanicaRiver, in the lower reach of the Savinja, Ri‘anaand Ledava rivers. Low discharges with 10- to20-year return period were measured on the Pe-snica and Kolpa rivers. The lowest discharges inAugust did not reach the lowest discharges ofthe period.

Precipitation in September, when therewas almost twice as much precipitation acrossthe country as in the comparative period of 1971-2000, influenced the increase of water quantityin rivers. The discharges in the western, centraland southern Slovenia rose to the level of highwaters, but only temporarily. Already in the se-cond half of October the river discharges appro-ached and later dropped below the mean low di-scharges for October. Graph 10 presents the meandaily discharges from May onwards for somegauging stations from different parts of Slovenia.Period discharges were added for comparison:mean monthly discharges (sQs); mean low di-scharges (sQnp) and lowest monthly discharges(nQnp).

The precipitation deficit in July and Au-gust caused a constant decrease of discharges,which lasted successively for almost two mon-ths. A continuous period with low discharges la-sted longer in 2001 than in 2000, when hydrolo-gical drought was also recorded. The amount anddistribution of precipitation in summer monthswas less favourable than in 2000, because of moreprecipitation in July 2000. The analysis of therunoff deficit for 2001 (with the exception of theupper Poso~je region) showed higher runoff de-ficit values in comparison with 2000. Even ma-ximum run-off deficits of continuous durationlargely exceeded the values in 2000. The dischar-ge threshold was 95% (Q95) taken from the du-ration curve, in hydrology commonly used as adischarge threshold. Examples of calculated va-lues are shown in Graph 11.

The analysis clearly shows the years withthe largest deficits, which are placed in the groupof hydrologically dry years. The comparison ofthe last two years with the period from 1960

dobo. Najmanj{i pretoki tudi v avgustu niso do-segli najmanj{ih obdobnih pretokov.

Padavine so v septembru, ko je skoraj poceli dr‘avi padla ve~ kot dvakratna koli~ina pa-davin primerjalnega obdobja 1971-2000, vplivalena pove~anje vodnatosti rek. V zahodni, osrednjiin ju‘ni Sloveniji so se pretoki rek dvignili tudido visokih voda, vendar le za kraj{i ~as. @e vdrugi polovici oktobra so se pretoki rek zopetpribli‘ali in kasneje tudi padli pod srednje maleoktobrske pretoke. Na grafu 10 je za nekaj po-staj iz razli~nih delov Slovenije prikazan poteksrednjih dnevnih pretokov od maja naprej. Zaprimerjavo so dodani obdobni pretoki: srednjimese~ni (sQs), srednji mali (sQnp) in najmanj{imese~ni pretoki (nQnp).

Primanjkljaj padavin v juliju in avgustuje povzro~il neprestano upadanje pretokov, ki jetrajalo nepretrgoma skoraj dva meseca. Nepre-kinjeno obdobje z malimi pretoki je bilo v letu2001 dalj{e kot v letu 2000, ko smo tudi bele‘ilipojav hidrolo{ke su{e. Koli~ina in razporeditevpadavin v poletnih mesecih je bila manj ugodnakot v letu 2000, ko je v juliju padlo ve~ padavinglede na julij 2001. Analiza primanjkljaja odto-ka za leto 2001 je dala, z izjemo zgornjega Poso~-ja, v splo{nem vi{je vrednosti primanjkljajevodtoka glede na leto 2000. Tudi maksimalni pri-manjkljaji odtoka neprekinjenega trajanja so vglavnem presegli vrednosti iz leta 2000. Za pre-tok praga smo vzeli 95 odstotni pretok (Q95) izkrivulje trajanja, ki se v hidrolo{ki praksi obi~ajnouporablja za pretok praga. Primeri izra~unanihvrednosti so prikazani na grafu 11.

Analiza nazorno prikazuje leta z najve~-jimi primanjkljaji, ki jih uvr{~amo med hidro-lo{ko su{na leta. Primerjava zadnjih dveh let zobdobjem od leta 1960 naprej ka‘e, da so se naobmo~jih, kjer je bila hidrolo{ka su{a v letih 2000in 2001 najhuj{a (Prekmurje in ju‘na Slovenija),primanjkljaji pribli‘ali najve~jim obdobnim vred-nostim. Hidrolo{ka su{a v letu 2001 torej ni bilaekstremen pojav v obdobju izvajanja meritev.Tudi najmanj{i pretoki v tem obdobju niso bilizabele‘eni. Je pa su{a regionalen pojav in ne zaja-me enakomerno cele Slovenije. V letu 2001 se jesu{a najbolj odra‘ala v severovzhodni Sloveniji,kjer je povpre~na letna koli~ina padavin najni‘ja,hkrati pa je bil primanjkljaj padavin najve~ji.

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Graf 11: Prikaz letnih primanjkljajev odtoka in maksimalnih primanjkljajev odtoka neprekinjenega trajanja za obdobje od leta 1960naprej.Graph 11: The presentation of the yearly run-off deficits of continuous duration for the period from 1960 onwards.

onwards shows that the deficits in the area withthe worst cases of hydrological drought in 2000and 2001 (the Prekmurje region and southern Slo-venia) approached the highest values of the pe-riod. The hydrological drought in 2001 was thusnot extreme in the period of taking measuremen-ts. The lowest discharges in this period were notrecorded as well. Drought is a regional pheno-menon and does not equally affect all parts ofSlovenia. The worst affected area in 2001 wasthe north-east of Slovenia where the average ye-arly amount of precipitation is lowest and at thesame time the precipitation deficit is the worst.

Krka je imela na vodomerni postaji Dvor najmanj{i letni pretokob koncu avgusta (foto: Jo`e Uhan).The Krka river reached the lowest annual discharge at thegauging station Dvor at the end of August (photo: Jo`e Uhan).

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VISOKE VODE V SLOVENIJILETA 2001Janez Polajnar

V letu 2001 ni bilo obse‘nej{ih poplav,kot smo jih bili vajeni v prej{njih letih. Nekolikoneobi~ajna je bila porazdelitev visokih vodapreko leta, saj se v jesenskem ~asu niso pojavilezna~ilne visoke vode. Reke so poplavljale v manj-{em obsegu, ve~inoma na obmo~jih vsakoletnihpoplav.

Prve visoke vode so se pojavile ‘e januar-ja, predvsem v zahodni in osrednji Sloveniji. Sle-dile so visoke vode v marcu, ko so zaradi obilnihpadavin in taljenja snega najbolj narasle reke vzahodni in ju‘ni, kasneje pa tudi v osrednji Slo-veniji. V preostalem delu leta, razen v septemb-ru, ni bilo visokih voda. Poletje je bilo suho zzelo majhno vodnatostjo rek. Predvsem v ju‘niSloveniji, na notranjsko kra{kem obmo~ju, Pri-morskem in {ir{em obmo~ju Dravskega polja sonekatere manj{e reke in potoki presahnili. V tem~asu je Agencija RS za okolje seznanjala in opo-zarjala javnost o {kodljivih vplivih poseganja vvodni prostor.

Slu‘ba za spremljanje hidrolo{kih stanj,napovedi in poro~anje Agencije RS za okolje jeleta 2001 zaznala 51 visokovodnih dogodkov, ko

HIGH WATERS IN SLOVENIAIN 2001Janez Polajnar

The year 2001 did not witness any majorfloods, as did the previous years. A slight devia-tion occurred in the distribution of high watersduring the year, since there were no typical highwaters in autumn. The rivers flooded to a smal-ler extent, mainly in the areas of yearly floods.

First high waters occurred already in Ja-nuary, mainly in the western and central Slove-nia. High waters in March followed, when wa-ters increased in the western, southern and laterin the central Slovenia due to abundant precipi-tation and snow melting. With the exception ofSeptember, the rest of the year witnessed no highwaters. Summer was dry, with low water levels.Small rivers and streams ran dry in southern Slo-venia, the areas of Notranjska and Kras, the Pri-morska region, and a greater area of the DravaPlain. During this time, the Environmental Agen-cy of the Republic of Slovenia pointed out andwarned the public about the bad influences ofintervention in water environment.

The Service for Monitoring Hydrologi-cal Conditions, Forecasts and Reports of theEnvironmental Agency of the Republic of Slo-

Graf 12: [tevilo prese‘enih pogojnih vodostajev slovenskih rek na opazovanih vodomernih postajah in gladine morja ob slovenski obalileta 2001 (po mesecih).Graph 12: The number of exceeded conditional water levels of the Slovene rivers at the monitored gauging stations in the year 2001 (bymonths).

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so reke na vodomernih postajah in gladina morjaob slovenski obali presegle pogojne vodostaje.To so vodostaji, pri katerih se za~neta izrednospremljanje in obve{~anje. Najve~ visokih vodaje bilo januarja (23), marca (14) in septembra (8).Preostale mesece je le gladina morja ve~krat pre-segla vrednosti, pri katerih se za~neta izrednospremljanje in obve{~anje (ve~ v prispevku o pli-movanju morja). Februarja, v obdobju medmajem in avgustom ter oktobra te vrednosti nisobile prese‘ene (graf 12).

Po podatkih Slu‘be za spremljanje hidro-lo{kih stanj, napovedi in poro~anje Agencije RSza okolje in Republi{kega centra za obve{~anjeso leta 2001 reke, potoki in morje 40-krat pre-stopili bregove rek ali morsko obalo ter se v manj-{em obsegu razlili. Poplavna voda v tem letu nipovzro~ila ve~je gmotne {kode na stanovanjskihin gospodarskih objektih, prometnicah in kme-tijskih povr{inah, kot jo je v prej{njih letih. Vodase je v ve~ini primerov razlivala na obmo~jihvsakoletnih poplav (preglednica 5).

Visoke vode januarja in marca 2001.Visoke vode v januarju niso pogoste, tokrat paso zajele ve~ji del dr‘ave, kar je prav tako dokajredek pojav. Prve visoke vode in visoko plimo-vanje morja so bili med 6. in 10. januarjem, dru-gi~ ob koncu meseca med 25. in 26. januarjem.Takrat so najve~ji pretoki nekaterih rek dosegli5-letno povratno dobo in reke so ponekod poplav-ljale. Zaradi obilnih padavin 7. in 8. januarja soreke zelo narasle sprva na zahodu dr‘ave, kasnejetudi v osrednji Sloveniji. Najbolj so se pove~alipretoki rek v Poso~ju, zgornjem toku Save in na

venia recorded 51 high-water occurrences in2001, when rivers at the gauging stations and thesea level on Slovene coast exceeded the criticalwater levels. This is when emergency monito-ring and notification begin. High waters weremost frequent in January (23), March (14) andSeptember (8). During the rest of the months,only the sea level exceeded the values at whichthe emergency monitoring and notification be-gin (more in the sea levels section). These valueswere not exceeded in February, the period betwe-en May and August and in October (Graph 12).

In the year 2001, there were 40 overflowsand floods registered (rivers, streams and the sea)according to the Service for Monitoring Hydro-logical Conditions, Forecasts and Reports of theEnvironment Agency of Republic of Slovenia andthe National Information Centre. The floods didnot cause extensive material damage on housingand economic facilities, traffic routes and agri-cultural areas as they did in the previous years.In most cases, the floods occurred in the usualflood prone areas (Table 5).

High waters in January and March2001. High waters are not very common in Ja-nuary; however, they have affected most of thecountry in January and March, which is a ratherrare event. First high waters and high tide occur-red between January 6 and 10, the second timeat the end of the month between January 25 and26. At that time, the highest discharges of somerivers reached a 5-year return period and the ri-vers flooded in some places. The increase in waterlevels was substantial due to abundant precipita-

Preglednica 5: Visoke vode in njihovo razlitje leta 2001 (po mesecih) (ARSO, CORS, razlitja manj{ih hudournikov niso upo{tevana).Table 5: High waters and overflowing in 2001 (by months) (ARSO, CORS, overflows of smaller torrents have not been included).

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Notranjskem, kjer je reka Reka pri Trp~anah vmanj{em obsegu poplavljala. Na Ljubljanskembarju se je na obmo~ju vsakoletnih poplav za~elarazlivati Ljubljanica.

Veliki pretoki rek so bili v zahodnih pre-delih dr‘ave vse do 24. januarja, ko so se pada-vine ponovno okrepile in zajele ve~ji del Slove-nije. 25. in 26. januarja so bile visoke vode vvsej dr‘avi. Reke so sprva najbolj narasle na zaho-du. Taljenje snega je dodatno pove~alo vodnatostrek na teh obmo~jih. Najbolj so narasle reke spovirji ob gorskih pregradah zahodne Slovenije,predvsem tiste s povirji v kra{kem Trnovskemgozdu. Idrijca in Vipava sta dosegli najve~je pre-toke z 2- do 5-letno povratno dobo in na izpostav-ljenih mestih poplavljali. Najve~ji pretok kra{-kega izvira Hubelj nad Ajdov{~ino je s 40 m3/sdosegel 5-letno povratno dobo. Pono~i 26. januar-ja so bile visoke vode tudi na rekah osrednje invzhodne Slovenije. Med njimi sta najbolj narasliGrada{~ica in Poljanska Sora, ki je v @ireh s pre-tokom 72 m3/s dosegla 2- do 5-letno povratnodobo. Obe reki sta na izpostavljenih mestih tudipoplavljali. Poplavljeno obmo~je ob Ljubljanicina zahodnem delu Ljubljanskega barja se je po-novno pove~alo. V tem ~asu je nara{~ala Savinja.Pono~i je v zgornjem toku dosegla pretok z 2-do 5-letno povratno dobo. Velik pretok Savinjeje dodatno pove~al vodnatost narasle Save, ki je‘e poplavljala v Zasavju. To no~ je poplavljalatudi Dravinja. V zgornjem toku v Lo~ah je dose-gla najve~ji pretok z 2- do 5-letno povratno dobo,proti jutru pa je ‘e poplavljala v srednjem toku,v okolici Polj~an in Maj{perka. Tudi Rogoznicapri Ptuju in Lo‘nica pri Polzeli sta poplavljali vmanj{em obsegu. V tem ~asu je poplavljala tudiKolpa. Najve~ji pretok v Radencih je zna{al 686m3/s, in ni presegel 2-letne povratne dobe.

Med 3. in 5. marcem so bile v ve~jemdelu dr‘ave ponovno visoke vode. Najdlje, vsedo konca meseca, so bile na kra{kih poljih No-tranjske, kar za ta letni ~as ni obi~ajno. Najve~jipretoki nekaterih rek so dosegli 5-letno povrat-no dobo. Reke so ponekod poplavljale.

V tem ~asu je bil ve~ji del dr‘ave prekrits sne‘no odejo. Odjuga in obilne padavine so med2. in 5. marcem povzro~ile naglo taljenje snegaod ni‘in do visokogorja. Te dni je bilo najve~padavin v zahodni, osrednji in ju‘ni Sloveniji.Ob toplem de‘ju se je sneg naglo talil, na No-tranjskem in Ko~evskem tudi do 10 cm na dan.

tion on January 7 and 8, at first in the westernpart of the state and later in the central part ofSlovenia. The discharges of rivers in the Poso~jeregion, upper reach of the Sava River and in theNotranjska region have increased the most dueto the flooding of the Reka River near Trip~e.The Ljubljanica River overflowed in the areawhere the floods occur every year.

River discharges have stayed high untilJanuary 24, when the precipitation increasedagain and spread across the greater part of Slo-venia. High waters could be found across thecountry on January 25 and 26. At first, rivers in-creased in the west. Snow melting additionallyincreased the water quantity in these areas. Ri-vers with headwaters in mountain chains of thewestern Slovenia increased the most, mostly tho-se with headwaters in the karstic Trnovski gozd.The Idrijca in Vipava rivers reached their highestdischarges with 2- to 5-year return period andflooded in exposed areas. The highest dischargeof the karstic spring Hubelj has reached 5-yearreturn period with 40 m3/s. On the night of Ja-nuary 26, high waters occurred in central andwestern Slovenia. The Grada{~ica and PoljanskaSora rivers (the Poljanska Sora River reached 2-to 5- year return period in @iri with 72 m3/s) in-creased the most. Both rivers flooded in exposedareas as well. The flooded area by the Ljubljani-ca River in the western part of the Ljubljanskobarje (Marshland) has increase again. At this time,the Savinja River increased as well. It reachedthe discharge of 2- to 5-year return period in theupper reach. The high discharge of the SavinjaRiver additionally increased the water quantityin the Sava River, which flooded in Zasavje aswell. The Dravinja River flooded in the same ni-ght. In the upper reach of Lo~e, it reached thehighest discharge with 2- to 5-year return periodand in the morning it flooded in its central reachin the vicinity of Polj~ane and Maj{perk. TheRogoznica River near Ptuj and the Lo‘nica Ri-ver near Polzela flooded to a lesser extent. TheKolpa River flooded at the same time. Its highestdischarge in Radenci was 686 m3/s and did notexceed the 2-year return period.

Between March 3 and 5, high watersagain occurred in most parts of Slovenia. Theystayed the longest (until the end of the month) inthe karstic fields of the Notranjska region, whichis not usual for this time of the year. The highestriver discharges reached a 5-year return period.Rivers flooded in some areas.

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Predvsem na pore~jih kra{kih rek na Notranjskem,pore~ju Kolpe in na pore~jih rek v alpskem inpredalpskem hribovju je dele‘ sne‘nice izdatnopove~al vodnatost rek in obseg poplavljenihpovr{in na kra{kih poljih.

@e pono~i 3. marca so se za~eli pove~e-vati pretoki rek na zahodu in jugu dr‘ave. Naj-ve~ji pretoki rek ta dan niso presegli 2-letne po-vratne dobe, le Reka je v okolici Ilirske Bistricepoplavljala v manj{em obsegu. Pono~i 4. marcaje ob ponovnih padavinah silovito narasla Kolpain v zgodnjih jutranjih urah dosegla v Radencihnajve~ji pretok 758 m3/s z 2- do 5-letno povrat-no dobo. Na izpostavljenih mestih je poplavlja-la. Ta dan se je poplavno obmo~je ob Ljubljanicina Ljubljanskem barju {e pove~alo, prav tako sose pove~evale poplavljene povr{ine na kra{kihpoljih Notranjske. V drugem delu dneva in pono~i5. marca so reke v zahodnem, ju‘nem in osred-njem delu dr‘ave po nekajurni prekinitvi za~eleponovno mo~neje nara{~ati. Najbolj so narasleIdrijca, Vipava, So~a, Sava v zgornjem in sred-njem toku, Savinja v zgornjem toku, Ljubljanicain Krka. V jutranjih urah 5. marca je poplavljalaIdrijca v spodnjem toku. Preplavila je cesto medSlapom ob Idrijci in Dolenjo Trebu{o. V zgor-njem toku, na vodomerni postaji v Podroteji, jedosegla najve~ji pretok 204 m3/s z 2- do 5-letnopovratno dobo. V tem ~asu je poplavljala tudireka Vipava v srednjem toku pri Velikih @abljah.Na vodomerni postaji Dolenje je bil zabele‘ennajve~ji pretok 143 m3/s. Narasla Idrijca in izda-ten dotok vode kra{kih izvirov na zahodnem deluTrnovsko-Banj{ke planote, so to jutro pove~alipretok So~e, predvsem v srednjem in spodnjemtoku. Na vodomerni postaji Solkan je bil zabe-le‘en najve~ji pretok 1280 m3/s z 2- do 5-letnopovratno dobo. ^ez dan so se pove~ali tudi pre-toki rek v osrednji Sloveniji, vendar niso preseg-li 2-letne povratne dobe. Le Sava je v popoldan-skih urah ob pretoku 1000 m3/s poplavljala naizpostavljenih mestih v Zasavju. Na meji sHrva{ko je najve~ji pretok, okoli 1450 m3/s, do-segla v poznih ve~ernih urah.

V prihodnjih dneh so se poplavljenepovr{ine na kra{kih poljih Notranjske {e pove~e-vale. Med drugimi je Mali Obrh v Lo{ki dolini7. marca poplavil ceste na obmo~ju [marate inKozari{~a. Visoke gladine vode na kra{kih poljihso se zadr‘ale do konca meseca. V zahodni inosrednji Sloveniji so se 13. marca pretoki rekponovno pove~ali. Najbolj v spodnjem toku So~e,

Most of the country was covered in snowat that time. Thaw and abundant precipitationhave caused a rapid snow melting from lowlandsto mountains. Most of the precipitation occurredin the western, central and southern part of Slo-venia. Warm precipitation caused the snow tomelt rapidly, in the Notranjska region and inKo~evje even 10 cm a day. The snow water sub-stantially increased water quantity in rivers. Italso increased the extent of flooded areas on kar-stic fields in the catchment areas of karstic riversin the Notranjska region, the catchment area ofthe Kolpa River and catchment areas of rivers inthe Alpine and pre-Alpine highlands.

In the night of March 3, the dischargesof rivers in the east and south of the country star-ted increasing. The highest discharges did notexceed a 2-year return period; the Reka Riverwas the only one to flood in the vicinity of Ilir-ska Bistrica. In the night of March 4, the KolpaRiver increased substantially and in the earlymorning reached its highest discharge in Raden-ci with 758 m3/s and a 2- to 5-year return period.It flooded in exposed areas. The flooded area bythe Ljubljanica River in the Ljubljana barje (Mar-shland) increased. At the same time, the floodedareas on karstic fields of the Notranjska regionincreased as well. The rivers started increasingheavily in the western, southern and central partof the country in the afternoon and in the nightof March 5. The Idrijca, Vipava, So~a and Savarivers increased the most in their upper and cen-tral reach, the Savinja, Ljubljanica and Krka ri-vers in its upper reach. The Idrijca River floodedin the lower reach in the early hours of March 5.It flooded the road connecting Slap ob Idrijci andDolenja Trebu{a. It reached its highest dischar-ge, 204 m3/s with a 2- to 5-year return period inits upper reach, at the gauging station Podroteja.The Vipava River flooded as well in its centralreach near Velike @ablje. The highest discharge,143 m3/s, was recorded at the gauging stationDolenje. The high waters of Idrijca and the in-flow of karstic springs in the western part ofTrnovsko-Banj{ka plateau increased the dischar-ge of the So~a in its central and lower reach. Thehighest discharge, the value of which was 1280m3/s and a 2- to 5-year return period, was recordedat the gauging station in Solkan. The Sava wasthe only river in the Zasavje region, which floo-ded in the afternoon in exposed areas with thedischarge of 1000 m3/s. It reached its highest

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kjer je najve~ji pretok zna{al 1178 m3/s. Pretokiostalih naraslih rek v osrednji Sloveniji ta danniso dosegli 2-letne povratne dobe.

discharge late in the afternoon at the Croatianborder, the value of which was 1450 m3/s.

The flooded areas in the karstic fields ofthe Notranjska region have increased in the fol-lowing days. The Mali Obrh spring flooded theroads in the [marata and Kozari{~e area on Mar-ch 7. High water levels in karstic fields stayedthere till the end of the month. River dischargeshave increased on March 13 in the western andcentral part of Slovenia. The greatest increaseoccurred in the lower reach of the So~a, the va-lue of which was 1178 m3/s. The discharges ofother flooding rivers did not reach a 2-year re-turn period.

Poplava na Ljubljanskem barju (foto: Janez Polajnar).Flood on the Ljubljansko barje (photo: Janez Polajnar).

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B. PODZEMNE VODE

PODZEMNA VODAVALUVIALNIH VODONOSNIKIHZlatko Mikuli~

Trend zni‘evanja gladin je bila prevla-dujo~a zna~ilnost re‘ima podzemnih voda v alu-vialnih vodonosnikih Slovenije v letu 2001. Pra-viloma so bile zaloge podzemnih voda povsodmanj{e na koncu leta kot v prvih mesecih. Po-letje je zaznamovala huda hidrolo{ka su{a, ki jezajela vse opazovane vodonosnike, razen tistih vLjubljanski in Celjski kotlini. V vodonosnikihseverovzhodne Slovenije je su{a trajala celo leto.Zaradi neugodnega vodnega re‘ima so bile v letu2001 povpre~ne gladine podzemnih voda pove-~ini pod letnim povpre~jem (Hs) dolgoletnegaprimerjalnega obdobja (graf 13, preglednica 6 inkarta 3). V Ljubljanski in Celjski kotlini so bilezaradi ve~je vodnatosti srednje gladine nad dol-goletnim povpre~jem, v vodonosnikih severo-vzhodne Slovenije pa zaradi hude su{e celo podnizkim dolgoletnim povpre~jem (Hnp).

Vi{ine gladin podzemnih voda v aluvial-nih vodonosnikih na Slovenskem so v splo{nemodvisne od ravnovesja med dotoki vode na enistrani, ter odtoki, izgubami in odvzemi na drugistrani. Viri napajanja vodonosnikov so padavinena samih poljih in v neposrednem padavinskemzaledju na obrobju ravnin, kakor tudi pronicanjeiz rek: Ledave, Mure, Drave, Savinje, Kamni{keBistrice, Kokre, Save, Vipave in So~e ter ostalihmanj{ih vodotokov na obmo~ju vodonosnikov.Odtoki podzemnih voda so posledica dreniranjav vodotoke, izgube pa so posledica evapotrans-piracije, ki je posebej pomemben dejavnik v plit-vih vodonosnikih severovzhodne Slovenije. Od-vzemi so predvsem s ~rpanjem za oskrbo z vodo,v {ir{em pomenu pa tudi odvajanje podzemnihvoda z melioracijskimi posegi. Za ocenjevanjevodnih razmer podzemnih voda je potrebno upo-{tevati prostorsko in ~asovno spremenljivost koli-~ine padavin, evapotranspiracije in vi{ino vodev rekah, ki mejijo na vodonosnike.

Klimatski dejavniki, ki so najbolj vpli-vali na re‘im podzemnih voda, so bili v splo{nemprimanjkljaj padavin in nadpovpre~no visoketemperature, od posameznih dogodkov pa obilne

B. GROUNDWATERS

GROUNDWATER IN ALLUVIALAQUIFERSZlatko Mikuli~

The decrease of water levels was a pre-vailing characteristic of the groundwater regimein Slovene alluvial aquifers in 2001. The ground-water reserves were low everywhere at the endof the year rather than at the beginning. A severehydrological drought occurred in summer. It af-fected all the observed aquifers, except for thosein the Ljubljana and Celje Basin. The aquifers inthe north-east of Slovenia suffered drought throu-ghout the year. The mean levels of groundwaterin 2001 were largely below the annual mean (Hs)of a multiannual comparative period (Graph 13,Table 6, Map 3) due to the unfavourable waterregime. The mean water levels in the Ljubljanaand Celje Basin were above the multiannualmean. Nonetheless, the aquifers in the north-eastof Slovenia were below the multiannual mean(Hnp) due to severe drought.

The groundwater levels in alluvial aqui-fers in Slovenia generally depend on the balancebetween the inflows on the one hand and out-flows, losses and withdrawals on the other hand.The sources of aquifer recharge are precipitationson the fields themselves and in the catchmentareas bordering on plains, as well as the infiltra-tion from the following rivers: the Ledava, Mura,Drava, Savinja, Kamni{ka Bistrica, Kokra, Sava,Vipava, So~a and other smaller watercourses inthe area of aquifers. Groundwater outflows are aconsequence of drainage into watercourses; thelosses are a consequence of evapotranspiration,which is a particularly important factor in theshallow aquifers of the northeastern part of Slo-venia. The water is mainly withdrawn for watersupply or some cases, for the reclamation of landby drainage. When estimating the condition ofgroundwaters the following has to be taken intoconsideration: spatial as well as temporal varia-bility of the amount of precipitation, evapotran-spiration and water levels in rivers bordering onaquifers.

Climatic factors influencing the ground-water regime the most were generally: precipita-tion deficit and temperatures above average. More

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sne‘ne padavine pozimi in spomladi v visoko-gorju ter huda poletna meteorolo{ka su{a.

Celoletna koli~ina padavin je bila manj{aod dolgoletnega povpre~ja na obmo~ju vseh alu-vialnih vodonosnikov. Primanjkovalo je od enedesetine do skoraj ~etrtine padavin. Za hidrolo{kire‘im podzemnih voda je bila pomembna pro-storska in ~asovna razporeditev primanjkljajev.Izpad padavin na celoletni ravni je bil najve~jina obmo~ju vodonosnikov severovzhodne Slove-nije, kjer je zna{al okoli ene petine na obmo~ju

specifically: snow precipitation in winter andspring in the mountains and a severe meteorolo-gical drought in summer.

The yearly quantity of precipitation wasbelow the multiannual mean on the whole areaof alluvial aquifers. A deficit from one tenth toalmost a quarter of precipitation could be wit-nessed. The spatial and temporal distribution ofdeficits was important for the hydrologicalgroundwater regime. The yearly precipitationdeficit was most severe in the north-east of Slo-

Graf 13: Primerjava zna~ilnih gladin podzemnih voda v letu 2001 z zna~ilnimi gladinami za primerjalno obdobje 1961–1990(Hs = srednja letna/obdobna gladina, Hnk = najni‘ja letna/obdobna gladina, Hvk= najvi{ja letna/obdobna gladina).Graph 13: Characteristic groundwater levels in the year 2001 compared to multiannual characteristic levels of 1961–1990 (Hs = meanyearly/periodic level, Hnk = the lowest yearly/periodic level, Hvk = the highest yearly/periodic level).

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Maribora, do skoraj ene ~etrtine na obmo~juPrekmurja. Drugod je primanjkovalo okoli enedesetine padavin. ^asovno so bili primanjkljajisklenjeno razporejeni v neugodnem letnem ~asuod aprila do avgusta, pomemben klimatski od-klon pa je bil tudi pribli‘no polovi~ni izpad pa-davin v zadnjih treh mesecih leta. V poznih jesen-skih mesecih je obnavljanje zalog podzemnihvoda obi~ajno najve~je. Ve~ kot v obravnavanemletu utegne ta jesenska klimatska motnja vplivatina re‘im podzemnih voda v naslednjem letu. Izra-zita meteorolo{ka su{a v poletnih mesecih jepovzro~ila primanjkljaj podzemnih voda v temobdobju. Izjemno obilno de‘evje v septembru, zve~ kot dvakratno obi~ajno koli~ino, je kon~alopoletno su{o v vseh opazovanih aluvijalnih vodo-nosnikih razen na obmo~ju severovzhodne Slo-venije. Ugoden vpliv na re‘im podzemnih vodaje imelo poleg tega de‘evja {e obilno sne‘enje vvisokogorju. Spomladi je sne‘na odeja na Kre-darici dosegla debelino rekordnih sedem metrov.Taljenje snega v gorah v pomladansko poletnemobdobju je pomembno prispevalo k bogatitvi za-log podzemnih voda na obmo~jih, kjer se vodo-nosniki napajajo iz rek Save, Kamni{ke Bistrice,Savinje in So~e.

Na obmo~ju vseh opazovanih aluvialnihvodonosnikov so bile v letu 2001 izgube vode zevapotranspiracijo nadpovpre~no velike, predvsemzaradi vi{je temperature zraka in nadpovpre~negason~nega obsevanja. Pri ve~ini vodonosnikov jebil odklon temperature za okoli poldrugo stopinjoCelzija, na obmo~ju Prekmurja celo nekaj ve~.Temu so najve~ prispevali nadpovpre~no toplipopoldnevi, kar je imelo v vegetacijskem obdobju,od pomladi naprej, za posledico nadpovpre~noveliko izgubo vode. Posebej velike izgube vodeso se vrstile iz meseca v mesec v vro~em poletju,ko je bilo zabele‘enih nadpovpre~no veliko vro~ihdni z najvi{jo dnevno temperaturo nad 30 stopinjCelzija. Vsega skupaj je bilo takih dni za en me-sec, na obmo~ju aluvialnih vodonosnikov zahod-ne Slovenije pa celo 39. Na obmo~ju ve~ine opa-zovanih vodonosnikov je bilo dni z najvi{jo tem-peraturo zraka nad 25 stopinj Celzija vsega sku-paj za dobra dva meseca, v zahodni Sloveniji celoza ve~ kot tri mesece. V takih razmerah je pove~anaevapotranspiracija v poletju mo~no na~enjala, za-radi pomanjkanja padavinske vode, ‘e tako pi~levodne zaloge.

Opisana razporeditev padavin se je od-ra‘ala tudi v prostorski in ~asovni porazdelitvi

venia, amounting from one fifth in the Mariborarea to almost one fourth in the Prekmurje area.In other areas the deficit amounted to one tenthof precipitation. The deficits were temporally di-stributed in an unfavourable time of the year, fromApril to August. An important climatic deviationwas a 50% precipitation deficit in the last threemonths of the year. The restoration of ground-water supplies is usually greatest in late autumn.This autumn climatic disruption is likely to havegreat influence on the groundwater regime in thefollowing year. A severe hydrological drought insummer months caused groundwater deficit inthis period. Abundant precipitation in Septem-ber with twice as much precipitation than usualended summer drought in all the observed allu-vial aquifers except in the north-east of Slove-nia. Besides the precipitation, heavy snow in themountains was also a favourable influence forthe groundwater regime. Snow cover in springin Kredarica was seven meters thick. Snow mel-ting in mountains in the spring-summer periodcontributed considerably to the increase of thegroundwater supplies in areas where aquifersrecharge from the Sava, Kamni{ka Bistrica, Sa-vinja and So~a rivers.

Water losses in 2001 were because ofevapotranspiration above average in all observedareas of alluvial aquifers, mainly due to high airtemperature and the insolation, which was abo-ve average. The temperature deviation in mostaquifers was about 1.5 °C, a bit larger in the Prek-murje area. The reason lies in the very warm af-ternoons, the consequence being the loss of wa-ter in the vegetation period from spring onwardsthat is above average. Water losses were espe-cially severe in summer months, when the num-ber of hot days was above average, with the meandaily temperature above 30 °C. There were about30 such days altogether, and 39 in the area ofalluvial aquifers in western Slovenia. There weremore than 60 days with the daily temperature abo-ve 25 °C in the area of most observed alluvialaquifers. In western Slovenia, there were evenmore then 90 days with such temperature. Incre-ased evapotranspiration caused even further de-crease of scarce supplies of rainwater.

The described precipitation distributionwas reflected in spatial and temporal distribu-tion of discharges or water level in rivers borde-ring on aquifers. Long-lasting dry periods werecommon and this was the reason for the discharg-

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pretokov oziroma vi{ine vode rek, ki mejijo navodonosnike. Zna~ilne so bile dalj ~asa trajajo~esu{ne razmere v vodotokih, zaradi ~esar je bilaceloletna koli~ina pretokov okoli ene desetinemanj{a od dolgoletnega povpre~ja. Vodnatost rekje bila pod povpre~jem skupno devet mesecev vletu. Najmanj{a je bila v avgustu in decembru,zaradi ~esar je bilo tedaj najmanj{e bogatenjepodzemnih voda s pronicanjem iz rek. Ugodenvpliv povr{inskih voda na ve~anje zalog podzem-nih voda je bil pomemben le v mesecih januarju,marcu in septembru, ko so vi{ine vode v rekahbile nadpovpre~no visoke. Opisani nenavadnire‘im povr{inskih voda je v celoti slabo vplivalna stanje zalog podzemnih voda.

Nizkega vodnega stanja na Sor{kem poljuin na delu Kranjskega polja ne ozna~ujemo zahidrolo{ko su{o, saj se primerjava nana{a na ob-dobje zvi{anih gladin podzemnih voda po izgrad-nji HE Mav~i~e leta 1986. Na tem obmo~ju segladine zadnjih nekaj let zni‘ujejo zaradi za-muljevanja dna zajezitvenega jezera hidroelek-trarne in s tem povezanega zmanj{anja pronicanjavode iz Save v podzemlje.

Zna~ilne letne gladine Hnk, Hs in Hvk(graf 13) so grobi pokazatelji vodnih zalog, ozi-roma hidrolo{kega re‘ima na celoletni ravni. Tistatisti~ni parametri omogo~ajo grobo ocenospremenljivosti v prostoru, ne morejo pa zajeti~asovne spremenljivosti med letom. Primerjavasrednjih letnih gladin Hs odra‘a dve pomembni

es being one tenth lower than the multiannualmean. Water quantity in rivers stayed below ave-rage for nine months. It was lowest in Augustand December and consequently the groundwa-ter recharge was then lowest as well. A favoura-ble influence of surface waters on the increaseof groundwater reserves was noteworthy only inJanuary, March and September, when the waterlevels were exceptionally high in the rivers. Theunusual surface water regime had a bad influen-ce on groundwater supplies.

A low water level in the Sora Plain andin a part of the Kranj Plain is not defined as hydro-logical drought, because the comparison refersto the period of raised groundwater levels afterthe construction of the hydroelectric power sta-tion Mav~ice in 1986. Water levels in this areahave been decreasing due to the silting-up of thebottom of the dam reservoir of the hydroelectricpower station, which result in decreased infiltra-tion from the Sava River.

Characteristic yearly groundwater levelsHnk, Hs and Hvk (Graph 13) roughly show wa-ter supplies or hydrological regime on a yearlylevel. Those statistical parameters allow a roughestimation of variability in space, but they can-not capture temporal variability during the year.The comparison of mean yearly groundwater le-vels (Hs) indicates two important characteristicsof the groundwater regime in 2001. The yearlygroundwater levels in the north-east of Slovenia,

Preglednica 6: Primerjava zna~ilnih gladin podzemnih voda v letu 2001 z zna~ilnimi gladinami primerjalnega obdobja 1961–1990.Table 6: Characteristic groundwater levels in the year 2001 and the characteristic levels of the comparative period 1961–1990.

* prekinjen ~asovni niz / interrupted time series

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zna~ilnosti re‘ima podzemnih voda v letu 2001.V vodonosnikih severovzhodne Slovenije, Vipav-sko-So{ke doline in Kr{ke kotline so bile srednjeletne gladine podzemnih voda ni‘je od primer-jalnega obdobja, kar je posledica izrazite polet-ne meteorolo{ke su{e in s tem povezanih ve~me-se~nih nizkih vodnih stanj. Srednje letne gladinev vodonosnikih Ljubljanske kotline in Celjskekotline so bile vi{je od obdobnih, kot posledicave~mese~nega obilnega napajanja vodonosnikaiz rek s povirji v visokogorju. V tem primeru jesne‘nica iz debele sne‘ne odeje nadome{~alaprimanjkljaje padavin. Na hudo su{o v severo-vzhodni Sloveniji ka‘e tudi primerjava nizkihletnih konic Hnk, saj so se tam gladine podzem-nih voda v letu 2001 zni‘ale celo pod raven naj-ni‘jih gladin primerjalnega obdobja. Kot posle-dica hidrolo{ke su{e na tem obmo~ju so bilenajvi{je letne konice Hvk dale~ pod obdobnimi,v nekaj primerih so se celo pribli‘ale ravni sred-njih obdobnih gladin. V severovzhodni Slovenijije bil celotni razpon nihanja gladin v letu 2001premaknjen navzdol. Analiza visoko vodnih ko-nic ka‘e {e eno posebnost. V dolini Kamni{keBistrice je bil leta 2001 prese‘en obdobni maksi-mum, kar pri~a, kako ekstremno velika je bilazaloga vode v sne‘ni odeji visokogorja v zaledjuvodonosnika. Zna~ilne letne gladine so podrob-no prikazane v preglednici 6.

the Vipava-So~a Valley and the Kr{ko Basin werelower than those in the comparative period, aconsequence of severe meteorological droughtin summer and several months of low water le-vels. Mean yearly water levels in the Ljubljanaand Celje Basin aquifers were higher than thoseof the period, a consequence of several monthsof abundant water reserve from rivers with head-waters in the mountains. Snow water from a thi-ck snow cover was a substitute for the precipita-tion deficit. The comparison of low yearly peaks(Hnk) also shows a severe drought in the north-east of Slovenia, since the groundwater levels in2001 fell below the lowest levels of the compa-rative period. The consequences of hydrologicaldrought in this area were low values of the high-est yearly peaks (Hvk). In some cases they appro-ached the mean levels of the period. The wholespan of level fluctuation in 2001 in the north-east of Slovenia moved downwards. The analy-sis of high water peaks reveals another peculia-rity. The maximum of the period was exceededin the Kamni{ka Bistrica Valley, which shows thesize of the water reserve in the mountain snowcover in the aquifers hinterland. Characteristicyearly levels are presented in detail in Table 6.

The regime of fluctuations of groundwa-ter reserves levels in 2001 was not conditionedonly by the previously mentioned factors but also

Karta 3: Srednje letne gladine leta 2001 v najve~jih slovenskih aluvialnih vodonosnikih.Map 3: Mean yearly levels in 2001 in major Slovene alluvial aquifers.

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Re‘im nihanja gladin oziroma zalog pod-zemnih voda v letu 2001 je bil poleg uvodomaopisanih dejavnikov vodne bilance pogojen tudi zre‘imom v predhodnem letu. V jeseni 2000 so vzadnjih treh mesecih izjemno obilne padavinepove~ale vodne zaloge nad povpre~je v prete‘nemdelu dr‘ave. Konec decembra 2000 so bile vodnezaloge nadpovpre~ne v vseh opazovanih aluvial-nih vodonosnikih, razen severovzhodne Slovenije.V nekaterih delih vodonosnikov Ljubljanske kotli-ne in Mirensko-Vrtojbenskega polja so vodne za-loge celo presegle visoko povpre~je Hvp. Slabostanje je bilo v velikem delu vodonosnikov seve-rovzhodne Slovenije, kjer je konec leta 2000 {evedno prevladovala su{a, ~eprav so bile zaloge vmanj{ih predelih vodonosnikov nad povpre~jem.Tako je bilo izhodi{~no stanje zalog podzemnihvoda na za~etku leta 2001 povsod zelo ugodno,razen v severovzhodni Sloveniji.

Glede ~asovne spremenljivosti hidrolo{-kega re‘ima v letu 2001 so bile tako velike razlikemed vodonosniki severovzhodne Slovenije invodonosniki v preostalem delu dr‘ave, da ta dvaprostorska sklopa opisujemo lo~eno.

Glavne zna~ilnosti re‘ima podzemnihvoda v severovzhodni Sloveniji so bile:

– su{ne razmere v nekaterih predelih vodonos-nikov ‘e od za~etka leta,

– med letom {iritev obmo~ij zajetih s hidrolo{kosu{o,

– razmeroma ustaljen re‘im z malimi amplitu-dami nihanja,

– tendenca zmanj{evanja vodnih zalog skozileto in

– razli~en re‘im na Vrbanskem platoju od pre-ostalih vodonosnikov tega obmo~ja.

Od januarja do maja se je stanje vodnihzalog v severovzhodni Sloveniji mo~no spre-minjalo. Osrednji del Prekmurskega polja in ve~jidel Dravskega polja je pestila hidrolo{ka su{a,medtem ko so bile v ve~ini vodonosnikov zalo-ge pod letnim povpre~jem. Na skrajnem zahod-nem in vzhodnem delu Prekmurskega polja sozaloge presegale srednje stanje. Od junija naprejso se obmo~ja hidrolo{ke su{e za~ela hitro {iritiin dosegla najve~jo prostorsko razse‘nost vizjemno suhem in vro~em avgustu. Nadpov-pre~no obilno de‘evje v septembru je sicer prehod-no prekinilo zni‘evaje gladin v teh vodonosnikih,vendar je su{o omililo le na omejenih manj{ih

by the regime of the previous year. In the autu-mn of 2001 (last three months) the water reser-ves have risen above average in most parts of thecountry. At the end of December 2000, theamount of water supplies was above average inall observed alluvial aquifers, except in the north-east of Slovenia. In some parts of aquifers in theLjubljana Basin and the Mirna-Vrtojba Plainwater supplies exceeded the high average (Hvp).Poor condition persisted in most aquifers in thenorth-east of Slovenia, where drought still conti-nued at the end of 2000, although the reserves insmaller parts of aquifers were above average.Groundwater reserves at the beginning of 2001were satisfactory everywhere, except in the north-east of Slovenia.

As far as temporal variability of hydro-logical regime in 2001 is concerned, there weregreat differences between aquifers of north-east-ern Slovenia and other aquifers, so they are di-scussed separately.

The main characteristics of the ground-water regime in the north-east of Slovenia were:

– Drought in some parts of aquifers from thebeginning of the year

– The areas affected by drought during the yearwere extended

– A relatively stable regime with low fluctua-tion amplitudes

– The water reserves were decreasing throu-ghout the year

– The Vrbansko plateau had a different regimefrom the rest of the aquifers in the area

The state of water reserves in the north-east of Slovenia has been changing heavily fromJanuary to May. The central part of the Prekmu-rje Plain and a larger part of the Drava Plain suf-fered from hydrological drought, but at the sametime the reserves in other aquifers were belowthe yearly mean. The reserves at the far west andeast part of the Prekmurje Plain exceeded themean state. The areas of hydrological droughthave started spreading quickly from June onwar-ds and reached its biggest spatial extent in extre-mely dry and hot weather in August. Abundantprecipitation in September that was above ave-rage temporarily interrupted the decrease of wa-ter levels in these aquifers, but only in limitedand small areas. Water levels were decreasingin the dry autumn, which only intensified thedrought. Hence, groundwaters in the north-east

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obmo~jih. Do konca leta so se gladine v suhi jese-ni zni‘evale, kar je stopnjevalo su{o. Tako sokoncem leta podzemne vode v severovzhodniSloveniji praviloma upadle na najni‘jo raven.

Izjema je bil vodonosnik Vrbanskega pla-toja, kjer je glavni vir napajanja pronicanje iz rekeDrave. Gladine so bile tam od marca do junijanad letnim povpre~jem, ko je bil zaradi taljenjasnega v visokogorskem povirju pretok reke ve-lik. V ostalih mesecih so bile gladine ni‘je odsrednje letne. Le v decembru se je tudi v temvodonosniku, kot v vseh ostalih vodonosnikihseverovzhodnega dela dr‘ave, pojavila su{a.

V preostalih opazovanih vodonosnikih podr‘avi se je leto za~elo z ugodnimi vodnimizalogami, glavne zna~ilnosti re‘ima podzemnihvoda pa so bile:

– ugodne oz. zelo ugodne zaloge podzemnihvoda na za~etku leta,

– prete‘no ugodne zaloge v prvi polovici leta,

– ugodno bogatenje s sne‘nico od pozne zimedo za~etka poletja s sne‘nico,

– kratkotrajna izrazita hidrolo{ka su{a v polet-nih mesecih,

– izjemno obilna in hitra obnova vodnih zalogv mokrem septembru,

– zni‘evanje zalog v suhi pozni jeseni in

– zaloge pod povpre~jem, ponekod ‘e hidrolo{-ka su{a na koncu leta.

Bogate vodne zaloge v decembru 2000in obilne padavine v januarju so dvignile gladinepodzemnih voda konec januarja nad letno pov-pre~je Hs, ponekod celo nad visoko povpre~jeHvp. Take izjemno bogate vodne zaloge, nadHvp, so bile na celem Kranjskem polju, v zahodnipolovici Ljubljanskega polja in gor vodnem deluvodonosnika doline Kamni{ke Bistrice podKrvavcem. Na Kranjskem polju, v predelu podKrvavcem, so se bogate vodne zaloge obdr‘alevse do za~etka maja. Temu je prispeval dotoksne‘nice iz tega dela Kamni{kih Alp.

V suhem februarju so se gladine povsodzni‘evale, vendar so visoke januarske zalogeomogo~ile ohranitev zalog nad povpre~jem. Podletno povpre~je so podzemne vode upadle le vnekaterih predelih Celjske kotline, Kr{ke kotli-ne in Mirensko-Vrtojbenskega polja.

Kljub pomanjkanju padavin so se gladi-ne podzemnih voda vse do poletja spreminjale v

of Slovenia dropped to the lowest level at the endof the year.

The aquifer of Vrbanski plateau was anexception, because the Drava is the main sourceof groundwater recharge. The levels were abovethe yearly mean from March till June, when thedischarge in the headwaters of the river was high,due to snow melting in the mountains. Water le-vels were lower than the mean yearly level du-ring the rest of the months. Drought affected thisaquifer in December as did every other aquiferin the north-east of the country.

The year started with favourable waterreserves in the rest of the observed aquifers acrossthe country. The principal groundwater regimecharacteristics were:

– Abundant groundwater reserves at the begin-ning of the year

– Relatively favourable groundwater reserves inthe first half of the year

– Favourable snow water supply from late win-ter till the beginning of summer

– A short-term, but severe hydrological droughtin summer

– Extremely plentiful and fast restoration ofwater reserves in the wet September

– Decrease of water reserves in the hot lateautumn

– At the end of the year reserves below average,hydrological drought affecting some areas.

Abundant water supplies in December2000 and abundant precipitation in January rai-sed groundwater levels above the yearly mean(Hs) at the end of January and in some placeseven above the high average (Hvp). These extre-mely plentiful water reserves above Hvp wererecorded in entrelly Kranj Plain, in the westernhalf of the Ljubljana Plain and in the upper partof the Kamni{ka Bistrica aquifer below Krvavecmountain. Abundant water reserves have beenretained until the beginning of May in the KranjPlain below Krvavec. An inflow of snow waterfrom this part of the Kamnik Alps was a valua-ble contribution.

Water levels were decreasing everywhe-re in the dry February, however, high Januaryreserves have made it possible for the reserves toremain above average. Groundwaters fell belowthe yearly mean only in some parts of the Celje

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razponu obi~ajnih letnih nihanj. Zaloge podzem-nih voda so bile v vodonosnikih, ki dobivajo ve~jidel vode s pronicanjem iz rek s povirji v visoko-gorju, vso prvo polovico leta prete‘no nad pov-pre~jem. Taljenje debele sne‘ne odeje v visoko-gorju je tako omogo~ilo nadpovpre~ne zaloge vvodonosnikih ob Savi na Ljubljanskem polju inKr{ko-Bre‘i{kem polju, v vodonosnikih ob Savi-nji v Celjski kotlini in ob Kokri na Kranjskempolju.

Pomanjkanje padavin in visoke tempera-ture zraka v poletnem obdobju so povzro~ile izra-zito zni‘evanje gladin, {e posebej v vro~em avgu-stu, ki je bil skoraj brez padavin. Koli~ina vodnihzalog je bila pred poletjem na Ljubljanskem polju,v dolini Kamni{ke Bistrice in v Celjski kotlinitako ugodna, da so se ohranile v razponu nor-malnih vodnih zalog tudi v obdobju meteorolo{kesu{e. V avgustu, ko je bil vi{ek poletne hidrolo{kesu{e podzemnih voda, je ta pojav zajel ve~ji delSlovenije. Ob ‘e prej su{ni severovzhodni Slo-veniji smo imeli tedaj su{o v nekaterih predelihLjubljanske kotline, manj{ih predelih Celjskekotline, prete‘nem delu Kr{ke kotline in v Vipa-vsko-So{ki dolini.

V izjemno de‘evnem septembru so sezaloge podzemnih voda obnovile na normalnoraven, v vsej Celjski kotlini pa nad povpre~je, vmanj{em predelu celo na raven zelo bogatih za-log z gladinami nad visokim povpre~jem Hvp. Vzadnjih treh su{nih mesecih so se gladine pov-sod zni‘evale, tako je konec leta ve~ji del Slove-nije ponovno zajela hidrolo{ka su{a.

Mese~na odstopanja gladin v letu 2001od mese~nih povpre~ij za primerjalno dolgolet-no obdobje (graf 14) ponazarjajo opisane poseb-nosti re‘ima tega leta. Izstopa celotno obmo~jevodonosnikov severovzhodne Slovenije, kjer seje celoletna hidrolo{ka su{a odra‘ala v negativ-nih odstopanjih mese~nih povpre~ij. Na temobmo~ju so bila odstopanja nenavadno velika,{e posebej v suhi pozni jeseni. Vodonosniki vseSlovenije ka‘ejo nekaj skupnih posebnostire‘ima. V septembru so bile gladine kljub izjem-no obilnemu de‘evju povsod pod povpre~jem zata mesec. To pri~a o hudi poletni su{i v letu 2001in velikem primanjkljaju podzemnih voda v av-gustu. Zadnja dva meseca so bile zaradi zelo red-kega pojava jesensko-zimske hidrolo{ke su{epodzemnih voda gladine povsod ni‘je od mese~-nih povpre~ij. Regionalna pestrost re‘ima se ka‘ekot odstopanje navzgor v prvi polovici leta na

Basin, the Kr{ko Basin and the Mirna-VrtojbaPlain.

Groundwater levels were despite the lackof precipitation fluctuating until summer in theusual way. Water levels in aquifers that receive alarge share of water with infiltration from riverswith headwaters in the mountains were mainlyabove average in the first part of the year. Themelting of a thick snow cover supplied abundantquantities of water reserves in aquifers near theSava River in the Ljubljana Plain and the Kr{koBasin, near the Savinja River in the Celje Basinand near the Kokra River in the Kranj Plainaquifer.

Lack of precipitation and high air tem-peratures in summer caused an exceptional de-crease in water levels, especially in the hot Au-gust with almost no precipitation. The quantityof water reserves in the Ljubljana Plain, theKamni{ka Bistrica Valley and the Celje Basin wasso favourable before the summer that there werereasonable quantities of water reserves left evenin the period of meteorological drought. In Au-gust, when the hydrological drought of ground-waters was at its peak, hydrological droughtaffected most of Slovenia: besides already drynorth- eastern Slovenia, some parts of the Ljub-ljana Basin, smaller parts of the Celje Basin, alarge part of the Kr{ko Basin and the Vipava-So~a Valley.

The extremely wet September saw a re-storation of groundwater reserves to a normallevel. Water levels in the Celje Basin rose aboveaverage and in a small part of the basin thegroundwaters rose substantially with levels abo-ve the high average (Hvp). Afterwards water le-vels were decreasing everywhere in the last threedry months, and the hydrological drought againaffected a larger part of Slovenia.

Monthly water-level deviations frommonthly mean in a multiannual comparative pe-riod in 2001 (Graph 14) present the distinctivefeatures of the regime in 2001. A whole area ofaquifers in the north-east of Slovenia stands out,since this year’s hydrological drought was re-flected in negative deviations from monthly me-ans. This area witnessed unusually sharp devia-tions, especially in the late and dry autumn. Theaquifers in Slovenia show some common featu-res. Water levels were despite abundant precipi-tation below average in September, which pointsto severe summer drought in 2001 and a consi-

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Graf 14: Odstopanja srednjih mese~nih gladin podzemnih voda v letu 2001, glede na srednje mese~ne gladine za primerjalno dolgoletnoobdobje 1961–1990.Graph 14: Deviations of mean monthly groundwater levels in the year 2001 from mean monthly levels in a multiannual comparativeperiod 1961–1990.

Ljubljanskem polju, odstopanje navzdol skorajcelo leto na Mirensko-Vrtojbenskem polju, od-stopanje navzdol od maja naprej na Kr{kem poljuin raznoliko odstopanje v Spodnje Savinjski do-lini, kjer je bila spremenljivost re‘ima najve~ja.

Pri letnem poteku nihanja gladin so bilezabele‘ene visoke konice leta prete‘no med ja-nuarjem in aprilom, le izjemoma ponekod v majuali juniju. Najvi{je letne gladine so bile najpogo-steje januarja ali marca, prav vse pa so bile vprvi polovici leta. Najni‘je letne gladine so bileve~inoma na prehodu iz avgusta v september,ponekod tudi konec leta. Letni minimumi so biliv poletju v ve~ini dr‘ave, konec leta pa prete‘nov severovzhodni Sloveniji. Prav tam so bile vdecembru na nekaj postajah zabele‘ene do tedajnajni‘je gladine v vsem dolgoletnem opazoval-nem obdobju. Severovzhodno Slovenijo je zaz-namovalo celoletno zni‘evanje gladin, tako je karprecej primerov z najvi{jo letno gladino naza~etku in najni‘jo na koncu leta.

Po splo{nih zna~ilnostih re‘ima podzem-nih voda je bilo leto 2001 nenavadno. Pravilomaso bile gladine v prvi polovici leta vi{je kot vdrugi. V obi~ajnih letih so gladine najvi{je v poznijeseni ob ve~kratnih prehodih vremenskih front

derable groundwater deficit in August. In last twomonths of the year groundwater levels were be-low monthly mean everywhere due to a very rarephenomenon of hydrological drought of autumn– winter period. A regional regime variety is pre-sented by deviations being above average in thefirst half of the year in the Ljubljana Plain andby being below average throughout the year inthe Mirna-Vrtojba Plain and in the Kr{ko Plainfrom May onwards and by a variable deviationin the Lower Savinja Valley where the regimechanges the most.

High yearly peaks were mainly recordedbetween January and April, and only exceptio-nally in May and June. The lowest yearly waterlevels were mainly recorded at the turn of themonth in August and at some places at the end ofthe year. Yearly minimum was reached in mostparts of Slovenia in summer and at the end of theyear, it was recorded mainly in the north-east.The lowest water levels in a multiannual obser-vation period were recorded in December in somestations in the north-east of Slovenia. The decre-ase of water level was observed in the north-eastof Slovenia throughout the year, and consequen-tly several cases of the highest water level at the

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~ez Slovenijo, ki prina{ajo obilne padavine. Vprvi polovici leta je v prete‘nem delu vodonos-nikov prevladovalo ugodno stanje vodnih zalogz gladinami nad obdobnim letnim povpre~jemHs. V drugi polovici leta so bile gladine, razenseptembra, praviloma ni‘je od letnega povpre~ja.

Leto 2001 je zaznamovala su{a. V neka-terih predelih vodonosnikov severovzhodne Slo-venije je bila hidrolo{ka su{a skozi celo leto. Vteh predelih su{a traja neprekinjeno ‘e od pom-ladi leta 2000. Decembra je pestila ve~ino Slo-venije huda hidrolo{ka su{a podzemnih voda, karje redek pojav. Zadnja zimska su{a pred tem jebila v zimi leta 1988/89. Izjemno nizka ravenzalog podzemnih voda na koncu leta 2001 je biloslabo izhodi{~e za re‘im nihanja zalog v letu2002.

beginning of the year and the lowest water levelat the end of the year were recorded.

The year 2001 can be described as unu-sual, judging by the general characteristics ofgroundwater regime. Water levels were general-ly high in the first half of the year. Normally, thewater levels are highest in late autumn whenweather fronts bringing abundant precipitationpass Slovenia. A favourable water reserves sta-tus generally prevailed in the first half of the yearwith water levels above the yearly mean of theperiod (Hs). Water levels were below the yearlymean in the second half of the year, with theexception of September.

The year 2001 was marked by drought.The hydrological drought lasted throughout theyear in some parts of aquifers in north-easternSlovenia. Drought has persisted in these partssince the spring of 2000. A severe hydrologicaldrought of groundwaters affected most of Slove-nia in December, which is a rare phenomenon.The last drought before that occurred in the win-ter of 1988/89. An exceptionally low level ofgroundwater supplies at the end of 2001 was nota favourable starting point for the regime of fluc-tuations of water supplies in 2002.

Zara{~ena struga Ledave pri vodomerni postaji ^entiba 31. avgusta 2001 (foto: Peter Frantar).Nearly overgrown channel of the Ledava River at the gauging station ^entiba on August 31, 2001 (photo: Peter Frantar).

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C. IZVIRI

HIDROLO[KI MONITORINGIZVIROVNiko Tri{i}

V letu 2001 se je nadaljeval hidrolo{kimonitoring izvirov, ki se je z vgraditvijo podat-kovnih zapisovalnikov na izvirih Divje jezero inPodroteja pri~el v letu 1999. Srednji letni vodo-staj je bil na izviru Podroteja nekaj centimetrovni‘ji od srednjega vodostaja v preteklih dveh le-tih, vendar je ‘e v mesecu januarju 2001 nastopilvisokovodni val, ki je presegel vse vrednosti vdotedanjem dvoletnem nizu izmerjene vrednostivodostajev. Konica vala se je pojavila na obehizvirih isto~asno, 25. januarja ob 20:30. Na izvi-ru Divje jezero je bil ob tem podatkovni zapiso-valnik preplavljen in je po nekaj dneh prenehaldelovati. Najvi{ji zabele‘eni vodostaj na izviruDivje jezero (616 cm) je bil za 54 oz. 97 centi-metrov vi{ji od najvi{jega vodostaja v letu 2000oz. v letu 1999. Na podlagi sledov visoke vodesmo ocenili, da je vodostaj na vodomerni postajiDivje jezero na Jezernici, ki je iztok vode izviraDivje jezero, dosegel okoli 245 cm. Ocenjenipretok ob tem vodostaju je med 70 in 75 m3/s.

Zaradi visokega vala je tudi srednja me-se~na januarska vrednost vodostaja v letu 2001najvi{ja v opazovanem nizu 1999-2001. Zaradiprekinitve delovanja merilnika v za~etku fe-bruarja nimamo na razpolago primerljivega nizapodatkov o Divjem jezeru za celotno leto 2001.Kljub temu je podatek o vodostaju visokega valadragocen, saj do sedaj nismo imeli ocene viso-kega pretoka iz Divjega jezera.

Podatkovni zapisovalnik, ki je vstavljen v~rpali{~e izvira Podroteja, je neprekinjeno bele‘ilpodatke o vodostaju, temperaturi in specifi~ni

C. SPRINGS

HYDROLOGICALMONITORING OF SPRINGSNiko Tri{i}

The hydrological monitoring of springsbegan in 1999 with the installation of data log-gers on Divje jezero (Savage Lake) in Podrotejaand continued in 2001. Mean yearly water levelin the Podroteja spring was a few centimetreslower than the mean water level in the last twoyears, however a highwater wave occurred whichexceeded all values in the two year series of wa-ter level measurements. The peak of the waveappeared on both springs at the same time, onJanuary 25 at 20:30. The data logger on Divjejezero (Savage Lake) was flooded and stoppedworking after a couple of days. The highest re-corded water level on Divje jezero (Savage Lake)(616 cm) was 54 or 97 higher than the highestwater level in 2000 or 1999. On the basis of highwater marks the water level on gauging stationDivje jezero (Savage Lake) on Jezernica (an ou-tflow of Divje jezero (Savage Lake) spring) wasestimated to around 245 cm. An estimated di-scharge value on this aquifer was between 70 and75 m3/s.

A mean January water level in 2001 wasthe highest in a series of observations from 1999till 2000 due to a high wave. We have no compa-rable series of data for the entire year 2001 be-cause of the data logger disruption at the beginn-ing of February. In spite of all that, the data aboutthe highwave level is very important, since therewas not any high discharge estimation from Divjejezero (Savage Lake) so far.

The data logger installed in the water-works Podroteja continuously recorded data on

Preglednica 7: Primerjava zna~ilnih nizkih, visokih (nk, vk) in srednjih (s) letnih vrednosti vodostajev, temperature in specifi~neelektri~ne prevodnosti na izviru Podroteja.Table 7: Comparison of characteristic low, high (nk, vk) and mean (s) annual water levels (H), temperatures (T) and specific electricconductivity (EP) on the water gauging station Podroteja.

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elektri~ni prevodnosti. Ker imata izvira podobenre‘im in skupno vodozbirno zaledje, lahko iz~asovnega razporeda podatkov za ta izvir skle-pamo na re‘im izvira Divje jezero v letu 2001.

Po prvem visokem valu v januarju je sle-dil drugi visoki val 5. marca, ki je bil le za 6centimetrov ni‘ji od prvega. Temu pa je sledilavrsta nekaj ni‘jih vodnih valov, ki so povzro~ilivisoko srednjo vrednost vodostajev v mesecumarcu. Kalnost ob nastopu visokih valov je ver-jetno vzrok za motnje v delovanju sonde zaspecifi~no elektri~no prevodnost. Zaradi nezanes-ljivih podatkov te veli~ine za leto 2001 ne poda-jamo.

V juliju in avgustu je bil le en srednjevisoki vodni val, sicer pa so vodostaji upadali inv avgustu in za~etku septembra je bil zabele‘ennajni‘ji vodostaj v opazovanih treh letih, 14 oz.15 centimetrov. Jesenski visoki val je 24. sep-tembra dosegel konico 179 centimetrov, kasnej{ivalovi pa so bili precej ni‘ji, kar je posledi~nopovzro~ilo tudi zelo nizek zimski minimum vdecembru z vrednostjo le 21 centimetrov.

water level, temperature and specific electricalconductivity. Since the two springs have a com-mon regime and a catchment area, it is possibleto establish the regime of Divje jezero (SavageLake) in 2001 with the help of the temporal datadistribution.

After the first high wave in January, asecond high wave followed on March 5, whichwas only 6 cm lower than the first. A series oflower water waves followed. They caused highmean water level value in March. The turbiditythat appears with high waves is probably the re-ason for interruptions in sensors for specificelectric conductivity. The data for 2001 wereunreliable; therefore they are not included here.

Only one middle height wave was record-ed in July and August, otherwise the water levelwas decreasing and in August and at the begin-ning of September the lowest water levels in threeyears of observations were recorded (14 or 15 cm).The high wave in autumn reached a peak of 179cm on September 24. The waves following wereconsiderably lower, which consequently causeda very low winter minimum in December (21 cm).

Graf 15: Srednji mese~ni vodostaji (cm) in srednje mese~ne temperature (°C) vode na izviru Podroteja v letu 2001.Graph 15: Mean monthly water levels (cm) and mean monthly temperatures (°C) in the Podroteja spring in 2001.

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D. MORJE

PLIMOVANJE MORJAIgor Strojan

Leta 2001 so bile gladine morja vi{je kotv dolgoletnem primerjalnem obdobju od leta1961 do 2000. Povpre~na letna vi{ina morja jebila 219,4 cm, kar je 3,3 cm vi{ja kot navadno.Povpre~na mese~na gladina morja je bila najvi{jamarca (232 cm), januarja (231 cm) in septembra(226 cm), kar je dokaj nenavadno, saj so pravilo-ma vi{ine morja v prvih treh mesecih leta najni‘-je, najvi{je pa oktobra in novembra. Najvi{javi{ina morja v letu 2001 (320 cm) je bila osmegajanuarja. Vrednost je 9 cm ni‘ja od dolgoletnegapovpre~ja najvi{jih letnih vi{in. Tudi najni‘jagladina morja v letu (127 cm), ki je bila drugegadecembra, glede na dolgoletno obdobje ni bilaekstremna. Vrednost je bila 11 cm vi{ja od pov-pre~ja v dolgoletnem obdobju. Preplavitve ni‘jele‘e~ih predelov obale so bile manj{e in manjpogoste kot navadno.

Vi{ine morja so v prvih treh mesecih letanajpogosteje nizke. V 40-letnem obdobju meri-tev vi{in morja v Koprskem zalivu je bila gladi-na morja v vseh prvih treh mesecih obdobja vpovpre~ju okoli 10 cm ni‘ja od celoletnegapovpre~ja obdobja, ki zna{a 216,1 cm. Leta 2001ni bilo tako. Povpre~ne mese~ne vi{ine gladinemorja so bile v prvih treh mesecih veliko vi{jekot v dolgoletnem primerjalnem obdobju: januar-ja 25 cm, februarja 9 cm in marca celo 28 cm.Januarja (231 cm) in marca (232 cm) sta bilipovpre~ni mese~ni vi{ini morja celo najvi{ji vletu 2001.

Januarja je bila gladina morja ve~ji delmeseca vi{ja od pri~akovane, le nekaj dni v sre-dini meseca je bila gladina ni‘ja. Najve~je odsto-panje je bilo v prvih desetih dneh, ko je morje{estkrat preseglo vi{ino 300 cm in v manj{i meripoplavljalo obalo. Na preseganje izra~unaneastronomske gladine morja je najbolj vplival ju‘niveter, ki je bil najmo~nej{i od {estega do devete-ga januarja. V tem ~asu so bile zabele‘ene velikeresidualne vi{ine, najvi{ja (75 cm) {estega januar-ja pozno pono~i. Posebej visoko je bilo morjesedmega januarja, ko je srednja dnevna vi{inazna{ala 265,2 cm. Najvi{ja vi{ina morja v mese-cu in obenem v letu (320 cm) je bila izmerjena

D. SEA

SEA LEVELSIgor Strojan

Sea levels in 2001 were higher than inthe multiannual comparative period from 1961till 2000. The mean annual sea level reached219.4 cm which is 3.3 cm higher than usual. Themean monthly seal level was highest in March(232 cm), January (231 cm) and September(226 cm), which is rather unusual consideringthat the sea level is generally lowest in the firstthree months and highest in October and Novem-ber. The maximum sea level (320 cm) was recor-ded on January 8, 2001. This value is 9 cm lowerthan the multiannual mean of the highest yearlypeaks. The minimum sea level in 2001 (127 cm)was recorded on December 2 and in comparisonwith the multiannual mean, it was not extreme.It was 11 cm higher than the multiannual mean.The sea did not flood the lower parts of the coastas frequently and extensively as in the previousyear.

The sea level was low in the first threemonths. In 40 years of sea level measuring in theGulf of Koper, the sea level was 10 cm lower inthe first three months than the multiannual mean(216.1 cm). This was not the case in 2001. Meanmonthly sea levels were substantially higher inthe first three months than in the multiannualcomparative period: 25 cm in January, 9 cm inFebruary and 28 cm in March. Mean monthlylevels in January (231 cm) and March (232 cm)were highest in 2001.

The sea level was higher than expectedfor most of January; there were only a few dayswith the sea level lower than expected. The high-est deviation occurred in the first ten days, whenthe sea exceeded 300 cm and flooded the coast.The south wind that was strongest from January6 to 9 was the cause of exceeded astronomic sealevel. High residual heights were recorded duringthis time, the highest being 75 cm in the night ofJanuary 6. The sea level was especially high onJanuary 7, when the mean daily height of 265.2 cmwas recorded. The highest sea level of the monthand of the year (320 cm) was recorded on Ja-nuary 8 at 8:26, and the lowest (144 cm) on Ja-nuary 12 at 16:58.

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osmega januarja ob 8:26, najni‘ja (144 cm) padvanajstega januarja ob 16:58.

Prvih deset dni februarja je bilo morjevi{je od povpre~ja, nato je bilo deset dni ni‘je inv zadnjih dneh meseca, ob izrazitem zni‘anjuzra~nega pritiska, zopet vi{je. Najvi{ja vi{inamorja v mesecu (288 cm), izmerjena osmega fe-bruarja ob 22:42, je bila nekoliko vi{ja kot je toobi~ajno za februar. Najni‘ja gladina morja138 cm je bila zabele‘ena 21. februarja ob 14:54.Tudi ta vrednost je med srednjo in najvi{jo ob-dobno vrednostjo. Morje je bilo marca 2001 zelovisoko. Srednja mese~na gladina morja (232 cm)je bila najvi{ja v letu in najvi{ja v mar~evskemdolgoletnem primerjalnem obdobju. Gladinamorja je bila ves mesec vi{ja od srednje obdob-ne vrednosti. Zelo visoko je bila predvsem v pr-vih dneh marca. Glede na dnevna povpre~ja jebila gladina morja najvi{ja ~etrtega marca, ko jebila srednja dnevna vi{ina morja 253,1 cm. Naj-vi{ja vi{ina morja v mesecu (303 cm), ki je bilanekoliko vi{ja od dolgoletnega mar~evskegapovpre~ja, je bila izmerjena osmega marca ob21:44. Gladina morja je bila najni‘ja sedmegamarca ob 14:02 (157 cm). Obi~ajno so najni‘jevi{ine morja marca veliko ni‘je.

Pomladi in poleti, v mesecih od aprila doseptembra, so povpre~ne mese~ne vi{ine morjav 40-letnem obdobju zelo malo odstopale odceloletnega povpre~ja obdobja. Za leto 2001 je

The sea level was above average in thefirst ten days of February, for the next ten daysit was low and again high in the last days of themonth when the barometric pressure droppedconsiderably. The highest sea level of the month(288 cm), measured on February 8 at 22:42, wasslightly higher than usual. The lowest sea level(138 cm) was recorded on February 21 at 14:45.This value was also between the mean and thehighest value of the period. March saw extre-mely high sea levels. The mean monthly sea le-vel (232 cm) was the highest of the year and thehighest of the multiannual comparative periodfor March. The sea level was higher than the meanvalues of the period throughout the month. It wasespecially high in the first days of the month.Considering the daily means, the sea level washighest on March 4, when the mean daily sealevel came up to 253.1 cm. The highest monthlysea level (303 cm), which was slightly higher thanthe multiannual March mean, was recorded onMarch 8 at 21:44. The sea level was lowest onMarch 7 at 14:02 (157 cm). The lowest sea le-vels in March are generally much lower.

The mean monthly sea levels in a 40-yearperiod deviated only slightly from the yearly va-lue of the period in spring and summer, from Apriltill September. In 2001 all mean monthly sea le-vels were generally higher than in the multian-nual period, yet at the same time they were con-

Graf 16: Januarja je bilo morje najvi{je v prvih desetih dneh meseca, ko je {estkrat preseglo 300 cm in je poplavilo ni‘je le‘e~e predele obale.Zaradi mo~nega ju`nega vetra in zni`anega zra~nega pritiska so bile gladine morja zvi{ane tudi do 75 cm.Legenda: Hmer – merjena vi{ina morja, Hres – residualna vi{ina morja.Graph 16: The sea level reached its peak in the first ten days of January, when it exceeded 300 cm six times and flooded the lower partsof the coast. Due to strong southerly wind and low air pressure measured sea levels exceeded astronomic sea levels up to 75 cm.Key: Hmer – measured sea level, Hres – residual sea level.

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zna~ilno, da so bile v tem delu leta vse povpre~nemese~ne vi{ine morja vi{je kot v dolgoletnemobdobju, vendar bistveno manj kot v prvih trehmesecih, v povpre~ju za 5 cm.

Aprila so bile vi{ine morja povpre~ne.Srednja mese~na vrednost 214 cm je bila podob-na srednji obdobni vrednosti. Maja je bilo morje,z izjemo prvih dveh dni, nekoliko vi{je odpri~akovanega. Posebno visoko je bilo med 14.in 18. majem, ko so se srednje dnevne vrednostigibale med 227,9 in 237,9 cm. Povpre~na mese~-na vi{ina morja (220 cm) je bila 6 cm vi{ja kotnavadno v tem mesecu. V naslednjem mesecu,juniju, so bile povpre~ne dnevne vi{ine morjave~inoma vi{je od srednje obdobne vi{ine, ven-dar so bile v {tirih kraj{ih obdobjih tudi nekolikoni‘je. Podobno kot v predhodnih mesecih so biletudi julija srednje dnevne vi{ine morja ve~inomeseca nekoliko vi{je od povpre~nih. Prve tri dnijulija je bilo morje ni‘je, nato pa do 21. v mese-cu precej vi{je od dolgoletnega povpre~ja. Zad-nje dni julija odstopanja niso bila velika. Podob-ne razmere so se nadaljevale tudi avgusta.Povpre~ne dnevne vi{ine morja so bile ve~inomeseca nekoliko vi{je od povpre~ja. Ni‘je so bilele v dveh obdobjih: 11. in 12. ter od 21. do 25.

siderably lower than in the first three months,5cm on average.

Sea levels in April were average. Themean monthly value (214 cm) was similar to themean value of the period. In May, however, thesea level was slightly higher than expected, withthe exception of the first two days. The sea wasespecially high between May 14 and 18, when themean daily values ranged between 227.9 and 237.9cm. The mean monthly sea level (220 cm) was 6cm higher than usual. The mean daily sea levelswere generally higher than the mean value of theperiod in June; yet, there were four short periodsof low values. Similarly, the mean daily sea levelswere slightly higher than average in July. The sealevel was somewhat lower in the first three daysof July, but from July 21 onwards, it was notablyhigher than the multiannual mean. There were nogreat deviations noticeable in the last days of July.Similar conditions continued in August. The meandaily sea levels were slightly higher than averagefor most of the month. Only two periods witnes-sed lower temperatures: August 11 and 12 as wellas August 21 to 25. There were no considerabledeviations from the average and they did not exce-ed 10 cm.

Graf 17: Marca so vremenske razmere ve~ji del meseca zvi{evale gladino morja. Na sliki so prikazani odkloni srednjih dnevnih vi{inmorja dH in odkloni srednjih dnevnih zra~nih pritiskov dP od dolgoletnih povpre~nih vrednosti. Dobro je razviden odnos med spremem-bo obeh merjenih parametrov. Ob zni‘anem zra~nem tlaku se gladina morja zvi{a.Graph 17: Sea levels got higher throughout the month due to weather conditions. The graph shows deviations of mean daily sea levelsdH and deviations of mean daily air pressure dP from multiannual mean values. The relation between the changes of both parametersmeasured is clearly visible. When the air pressure drops, the sea level rises.

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Graf 18: Izmerjene urne (Hmer) in izra~unane astronomske (Ha) vi{ine morja avgusta 2001. Izmerjene vi{ine morja so le malo odstopaleod izra~unanih astronomskih. Izhodi{~e izmerjenih vi{in morja je mareografska »ni~la« na mareografski postaji v Kopru. Srednja vi{inamorja v dolgoletnem obdobju je 216,1 cm.Graph 18: Measured hourly (Hmer) and calculated astronomic (Ha) sea levels in August 2001. Measured sea levels deviated onlyslightly from the calculated astronomic levels. The starting point for the measured sea levels is the mareographic ’zero’ on the Kopermareographic station. The mean sea level of the multiannual period reached 216.1 cm.

avgusta. Odstopanja od povpre~ja niso bila veli-ka in niso presegala 10 cm.

Septembra so bile vi{ine morja najvi{jev opisanem ve~mese~nem obdobju. Povpre~nednevne vi{ine morja so bile ves mesec vi{je odpovpre~ja septembrskega dolgoletnega povpre~-ja. Povpre~na mese~na vi{ina morja v septemb-ru (226 cm) je bila 11 cm vi{ja kot navadno vtem mesecu in tako med najvi{jimi v primerjal-nem obdobju.

Oktobra in novembra so vi{ine morjanavadno najvi{je v letu. Vremenski in drugi vplivina vi{ino gladine morja so v teh dveh mesecihnajve~ji. Oktobra je povpre~na vi{ina morja vdolgoletnem primerjalnem obdobju 220 cm, no-vembra pa 223 cm. To je obdobje, v kateremmorje najve~krat preplavlja ni‘je le‘e~e predeleobale. Leta 2001 so bile vi{ine morja oktobra inpredvsem novembra ni‘je kot obi~ajno. Novemb-ra je bila povpre~na mese~na vi{ina morja (213cm) 10 cm ni‘ja kot navadno. Morje je le v nekajprimerih in v manj{i meri preseglo vi{ino 300cm, pri kateri pri~ne preplavljati ni‘je predeleobale.

The sea levels in September were thehighest in the period of several months. The meandaily sea levels were higher than the multiannualSeptember mean throughout the month. Themean monthly sea level in September (226 cm)was 11 cm higher than usual and therefore oneof the highest in the comparative period.

The sea levels in October and Novemberare usually the highest of the year. Weather in-fluences and other influences are usually thestrongest in these two months. The mean sea le-vel in October in a multiannual comparative pe-riod reached 220 cm and 223 cm in November.This was the period of biggest over-flows overlower parts of the coast. The sea levels in Octo-ber and November 2001 were lower than usual.The mean sea level in November (213 cm) was10 cm lower than usual. There were even somecases when the sea levels exceeded 300 cm andstarted flooding the lower parts of the coast.

The mean sea level in October was only1 cm lower than usual. Considering the expectedastronomic levels, sea levels in November chan-ged considerably. Lower than average sea levels

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Povpre~na vi{ina morja v oktobru je bilale centimeter ni‘ja kot navadno. Novembra sose odstopanja gladin morja, glede na pri~akovaneastronomske vi{ine, zelo spreminjala. Morje jebilo prvih nekaj dni ni‘je od povpre~ja. Slediloje desetdnevno obdobje s povi{animi gladinami.To obdobje je imelo dva vi{ka, ob drugem je biladose‘ena najvi{ja gladina v mesecu. V drugi po-lovici meseca so bile gladine spet ve~inoma ni‘jeod povpre~ja. Najvi{ja gladina morja 305 cm jenastopila {tirinajstega novembra ob 8:12.Meteorolo{ka situacija je bila za povi{anje mor-ske gladine nekoliko nezna~ilna. Residualna vi{i-na je bila 43 cm. Pihala je burja. Hkrati pa je vju‘nem Jadranu pihal mo~an jugo, ki je vodonarival proti severu. K povi{anju gladine je pri-spevalo tudi mo~no zni‘anje zra~nega pritiska.

Decembra so bile vi{ine morja, razen zad-njih dni v mesecu, ni‘je od dolgoletnega pov-pre~ja. Povpre~na mese~na vi{ina morja je bila208 cm. Srednje dnevne gladine morja so bilevi{je od srednjih obdobnih vrednosti le v zadnjih{estih dneh decembra, ko je bila dose‘ena tudinajvi{ja mese~na vrednost. Najvi{ja gladinamorja (302 cm) je bila zabele‘ena tridesetega de-cembra ob 8:38, najni‘ja (127 cm) pa drugegadecembra ob 16:00.

could be observed in the first few days. A ten-day period of raised sea levels followed. Thisperiod recorded two peaks, with the highest sealevel of the month during the second peak. Sealevels were lower than average in the second partof the month. The highest sea level reached 305cm and was recorded on November 14 at 8:12.The meteorological situation was somewhat unu-sual considering the raised sea level. The resi-dual height reached 43 cm. A strong northeastwind (burja) was blowing. The jugo wind (a south-eastern wind of moderate strength) was blowingat the same time in the south Adriatic and push-ed the water towards the north. A considerabledecrease of barometric pressure contributed tothe sea level rise.

With the exception of the last days ofDecember, the sea levels were lower than themultiannual mean. The mean monthly sea levelheight reached 208 cm. The mean daily sea le-vels were higher than the mean values of the pe-riod only in the last six days of December, whenthe highest monthly value was reached. The high-est sea level (302 cm) was recorded on Decem-ber 30 at 8:38, and the lowest (127 cm) on De-cember 2 at 16:00.

Graf 19: Meteorolo{ka situacija je v za~etku decembra pogojevala vi{ine morja, ki so bile ni‘je od napovedanih. Burja je odrivala vodnemase od obale, visok zra~ni tlak pa je gladino morja {e zni‘eval.Legenda: dP – odstopanje od povpre~nega zra~nega pritiska, Vv – hitrost vetra, Vs – smer vetra, Hmer – merjena vi{ina morja, Ha –astronomska vi{ina morja.Graph 19: Meteorological situation at the beginning of December influenced the sea level, which was lower than forecasted. A strongnorth east wind pushed the water away from the coast, and high barometric pressure caused a decrease in the sea level.Key: dP – deviation from mean barometric pressure, Vv – wind speed, Vs – wind direction, Hmer – measured sea level, Ha – astronomicsea level.

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