krishna river water harnessing

8/6/2019 Krishna River Water Harnessing

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N.SASIDHAR

Are pumped storage schemes beneficial forharnessing the Krishna river 'water further?

The demandfor water from the river Krishna surpasses thewater available in the river. The 75% dependable wateravailable in the river will be completely harnessed in nextfew years. Substantial quantity of water is available at 50%dependability over the water available at 75% dependabil-ity in the river. This conceptual paper examines the techno-economic feasibility of harnessing this unreliable wateravailable during good monsoons for irrigation needs andpower generation by pumped storage schemes.

I.,troductionThe river Krishnahas drainage area of 2,58,948sq.km of w hich 26.8% lies, in M aharastra, 43.8%in Karnataka and 29.4% in Andhra Pradesh (AP).It ha s two major tributaries which are Tungabhadra andBhim a rivers. The Bhim a joins K rishna just before enter-ing into A P and Tungabhadra joins K rishna ncar K um ooltow n (F ig.l) in AP. K rishna river after the confluence ofTungabhadra passes through a narrow gorge for a distanceof 130 km in which two large reservoirs, Srisailarn andN agarjuna Sagar are located. T hese reservoirs create a hy-draulic head of nearly 90 m eters each, w hich have been har-n es sed for gener at ing hyd roel ec tr ic (HE) power.II.1I , \ Water availabilityB eing a peninsular river. m ost of the w ater flow in the riveris during south west monsoon which lasts for about fourmonths duration. A typical hydrograph of the. river atV ijayaw ada during m onsoon season is show n in F ig. 2. Thew ater availab le in the river sho ots up fro m neglig ib le q uan -tily in the m iddle of July and b ec omes n eg lig ib le a br up tlyafter th e sec on d w eek o f Nov em be r. T he d isc harg e in th e ri vc ris n eg lig ib le d urin g res t o f th e y ear. T he m ax im um d isc harg eof this river is 33,810 cum ecs (m J/scc) and the m inim um isless than 3 cum ecs. T he total annual m ean. r unoff is 67:675m illio n c ub ic mete rs 0'1' 2390 thousand m illion cubic feet('fM C). The w ater run off in the river vary w idely from yearto year and month 10 month depending on the vagaries ofM r. N . S as id ha r, M an ag er. N TP C L td . H yd cra ba d.

INDrAN JO URNAL O F PO WER &. R iV ER V AL LE Y D EV EL O PM E NT

'the m onsoon. It has been estim ated that 75% dependableyield in the river is 2060 TM C and is allocated among theriparian states of Maharastra, Karnataka and AP byB achavat T ribunal. H ow ever. A P is allow ed to use the ex -cess w ater available in the river during better m onsoon pe-riod s up to the year 2000 AD when tribunal aw ard w ill bereview ed. A Pis already utilising its fut'l share of w ater andtrying to use the surplus w ater. K am ataka add M aharastraare m aking th eir fu ll efforts to utilise their share of w aterby~OOOAD.

Water requirementThe cultivable area and net sown area are 78% and 60% ofthe geographical area of the river basin respectively. 100h igh pe rcentage of sow n area co upled w ith sem iarid w eatherconditions in this river basin increases the water- demandf or irr ig atio n n ee ds . In addition the ad jo in in g P cn nar riv erbasin w hich is perennially drought prone area w ith scantyrain fall, further raises the w ater dem and for its irrigationneeds from the K rishna river. M oreover. K rishna river hasgood potential for pow er generation w hich ha s been har-nessed mostly by Koyna. Srisailam , Nagarjuna Sagar HEstatio ns and few H E station s C onstructed by T atas in p rivatesector. The dem and for w ater is unlim ited from th is riv ersince gen eratin g H E po wer is h ig hly profitab le.NeEDS FO R PU MPED STO RAGE RESERVO IRS

T he ab ov e fa cto rs n ece ss itate to m ake use of the avail-able w ater in th~ K rishna river to th e m axim um ex tent ei-ther (or po wer g eneration o r irrig ation. M ore than 800 T MCo f un reliab le w ater is availab le at 5 0% d ep end ability abo ve2060 TM C of 75% dependable water d urin g g oo d m on so onyears. The quantum of water that had gone into sea from1972 to 1992 is shown in Table 1. Sub sta ntia l q ua ntity o fthis water has overflowed downstream on the spillway ofdam s during floods w ithout even being used for secondarypow er generation in the existing H E stations. Full utilisa-t ion can be a ch ie ve d b y c re atin g la rg e re se rv oir s to s to re f loodw ater during good m onsoon years w hich otherw ise go w asteinto sea. This stored flood w ater ean be p ut 10 use eith er forpow er g eneration o r irrigation needs.

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TA .OU l 1 WA .T P1 { D R AIN ED IN TO S EA .Monsoon year Wa l J! r d ra in ed(June to May) into se a (fMC)

197273 16 3197374 1217197475 97 8197576 2 5 9 2197677 1039197778 64 0197879 1867197980 85 5198081 1068198182 1239198283 456198384 1481198485 33 2198586 157198687 13 6198788 N O ( AVlilal>le.198889 1244198990 N O ( AVlilable.199091 1045199192 1204199293 323

N early 1 40 0 T M C o f sto rage capacity is already createdor in advanced stage of creation till now . It w ould be diffi-CUl l 10 identify further new storage reservoirs on the m ainriv er w ith le ss su bm erg en ce a re a Howev er s to rag e c ap ac ityca n be c re ated o n the minor/medium tributary riv ers w hicha re d ir ec tly empty in g in to th e e xis tin g s to ra ge re se rv oir s s uc has S risailam . Ju rala, N agarju na S agar. etc., b y en visag in gp um pe d s to rag e s ch em es (P SS ).

A typical P SS consists of an upper reservoir, H E pow erstatio~ .an d a d ow nstream reserv oir. T he H E po wer stationh as a n a dd itio na l f ea tu re o f re ve rs ib le tu rb in e c ap ab ility ( i.e .tu rb in es c an be used as pum ps 10 lift w ater to higher levelby con su min g electricity). W h en w ater is available. this H Estation pum ps w ater into upper reservoir from the dow n-stream reserv oir an d stores for fu ture uses. This stored w a-ter is released through HE turbines into downstreamreser vo ir . g ener at ing e le ct ri ci ty whenever r equ ir ed .

These proposed P SS pum p w ater from the existing stor-age reservoir (dow nstream reservoir) located on the m ainriv er in to a n u pp er s to ra ge re se rv oir lo ca ted o n its trib uta ryd urin g m on so on s ea so n. T his w ate r is re le as ed in to th e d own-stream reservoir during non m onsoon season for furtherpo wer g en eration in th e d ow n stream H E p ow er statio ns an d/o r ir rig atio n n ee ds .

Advantage of PSST he adv an tages o f P SS w hich m ake it m ulti-p urpo se and

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eco no mically viab le are g iven belo w:1. It stores flood w ater to utilise during bad m onsoon years.2. It consumes the surplus power during m onsoon season

p rev en tin g th erm al p ow er s ta tio ns fro m b ac kin g d own be-cause o f secon dary p ow er av ailab ility fro m H E S tatio ns.

3. C heap im ported pow er from adjacent R egional E lectric-ity Boards or State E lectricity Boards can be used forp um ping requ irem en ts du ring m on so on season .

4. It can also be used as a truly peaking pow er station tomeet .daily as w ell as seasonal peak demands.

5. It generates m ore pow er than w hat it consum es providedH E stations w ith fairly good hydraulic head are locateddow nstream on the river.

6 . The stored water can be used fo r cre atin g irrig atio n fa-c ilitie s an d/o r d rin kin g w ate r req uirem en ts .

7 . This stored water can be u tilis ed to co ntro l th e s alin itying ress in estu aries an d to m ain ta in th e riv er reg im e af-ter using for pow er generation. B achavat A ward has notallocated w ater out of 75% dependable yield of K rishnariver for this purpose. How ever, the recent opinion ofex perts is that ten (10% ) p ercent o f7 5% d ep en dable w aterof m ajor riv ers sh all be sp ared fo r th is p urp os e.

Suitable location of PSSSom e of the suitable sites for locating these P SS can be ex -plo red u pstream of S risailarn reserv oir o n th e m ediu m/m i-nor rivers w hich arc directly em ptying into it because of thefollowing advantages. .1. Most of. the flood water during good monsoon yearspasses through this dam since the river at this point C ov-

ers 80% ;of the total catchm ent area.2. Being a large reservoir of capacity nearly 200 TM C. i,

can retain the peak flo od w ater an d m ake available 10 th ePSS over a period of time to pump into the upper reser-voir.

3. Fairly good hydraulic head (90 to 210 metres) is avail-able to generate ad ditio nal h yd ro p ow er b y usin g th is sur-p lu s w ater befo re pu tting to ir rig atio n u se s. T his aspectm akes the P SS econom ically viable because it allow s tog en erate m ore po wer w ith th e stored flood wa te r th an thepow er consum ed to pum p into the storage reservoir.

4 . Srisailam HE station has 770 M W under operation andanother 900 M W is under advanced stage of construc-tion. T his peaking H E station w ould m ake available sec-ondary power during monsoon period to nearby PSSw hich redu ces transm ission lines cost an d transm issionlosses.

5 . The water stored by the PSS can be used as carry for-ward storage to advance the sowing activity in theK rishna Delta, Nagarjuna Sagar command area and

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. . .l) Pulichintala (proposed)2) Nagarjuna Sagar3) SrisaiJam4) Iurala5) Tungabhadra

6) Bhsdra7) Narayanapur8) Almaui9) Koyna10) Bhima

. ". .+.. .- -

- . .. . . - - 1 - - - _ _ _ _'. - . .o

Fig.I Basin plan of the river Krishna

Srisailam command area, to match w ith the onset ofm onsoon w ithout w aiting for sufficient inflow s into theN agarjuna Sagar and Srisailam reservoirs. In this w ay itwould be beneficial to grow long duration or m ultipleirrigated crops. S o the w ater stored by the P SS gives enor-m ous flexibility in the better m anagem ent of availablewater to m axim ise the benefits to irrigation and pow ergeneration.

6. M any irrigation schem es are under construction or con-tem plation draw ing w ater from S risailam reservoir suchas Srisailam R ight B ank Canal, H indri-N eeva, T eluguG anga, V elugodu, G aleru N agari, K .C . Canal rem odel-ling, Srisailam left B ank Canal, etc. These schem es en-visage storing required w ater in balancing reservoirs.T hese reservoirs w ill receive w ater through flood canals

INDIAN JO URNAL O F PO WE R & R IV ER V AL L EY D E VE L OP M[ ~" -r

from the Srisailam reservoir w hen flood w ater is avail-able. The PSS option is better alternative to 'balancingreservoirs w ith associated flood canals' since it can sup-ply w ate r to th ese irrig atio n sc heme s th ro ug ho ut th e c ro p-ping season by releasing w ater into Srisailam reservoir.T he canals of irrigation schem es can be just sized to sup-ply the water throughout the irrigation period fromS risailam reservoir. T here w ill be s ub st an ti al r ed uc ti onin the cost of these irrigation schem es by avoiding theexpenditure on balancing reservoirs and flood canals dueto P SS.

C.~'1 Si un II'S:In case, a storage reservoir of live capacity 318 TMCalong with a pum ped storage HE Station is to be created ona medium /minor river which is emptying directly intoSrisailam reservoir, this reservoir acts as upper reservoir for

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T ABL8 2 B I !N I F IT S f ROM 111E P SS I N VARlOOUS C OM BlNA11 0NS Of' MONSOON I IB IlAVlORSuoocuive

IW OmoruoorubcMviour.

AVI ilability ofcarry forwlprdItorajigcfromprevious year.

W lta lu pply toirrigation systemsdoWlUIIUm ofSrillilarn Dam.

W a ta lu pp ly toi rr igation systamfrom Srisailamreservoir,

Creation ofc.ury fOfW. rdl to ra ge f or n ex t

year.( ' ; ' pSGSSGO

YESNONOYES

YE SYESN

YFSYFSNOYFS

NOYE SNOYES

B -> Sad monsoon ycar .q -> Good I1lOIUOOO yeatlr. Cropping 'Sowing activity"atarts w it h t he onset of monsoon (June lst). O t he rw is e i tslArtS in t he middl e of J ul y mon th ." E x is ti ng o ld i rr ig at io n s ch eme s w il l be given pr ior i ty in supply of ava ilable wutcr.

I.

F ig. 2 Hydro graph of Kri shn a a nd Goda va ri rivers in 1973 monsoon periodthe p um ped sto rag e H E statio n and S risailam reserv oir actsas ~ dow nstream reservoir. W h en the flood w ater is a va il-abl~ in the Srisailam reservoir. water is pum ped into theupper reservoir by operating the H E turbines in pum pingm ode. T his sto red w ater is released in to S risailam reservo irb y o pera tin g H E tu rb in es in tu rb in e mod e w hen ev er req uire dto m eet irrig ation an d/o r p ow er g en eratio n n eeds

It is assum ed that flood w ater can be pum ped into upperreservoir for 90 days (2160 hours) at the rate of 1157.4cu mccs from th e S risailam reservo ir du ring goo d m on so onseaso n. T he evapo ration and seepage lo sses in th e u pp er res-ervoir is assum ed eq ual to inflo ws from its c atc hme nt a re a.

The follow ing two cases are examined for which thiss to re d wat er c an be put to use:1. Case I: The water is used for power generation in the

S risailam H E station (90 m eters head), N ag arjuna S ag ardam HE station (90 meters head) and proposedP ulichin tala H E statio n (3 0 m eters h ead) b efo re lettin ginto sea w ithout any irrigation usage. So 210 m eters to-

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ta l hydraul ic head is a va ila ble in th e d ow n stre amof P SS fo r p ow er g en eratio n,

2. Case 2 : A t present sufficient infiow into theN ag arju na S ag ar an d S risa ila m re se rv oirs is notta kin g p lac e till th e late r half of July m onth com -polling farmers to start so win g a ctiv ity in th e se c-ond half of July m onth every year. It is proposedto use the stored w ater by the P SS for irrigationin Krishna D elta, Nagarjuna Sagar com manda nd Pulic hin ta 1a c ommand ( pr op os ed ) b ef or e s uf -ficient inflow takes place in the reservoirs byad va nc in g th e c ro p so win g ac .tiv ity to m atc h w iththe onset of monsoon (i.e. June Ist}.W hen thep ro po se d P ulich in ta la rese rv oir alo ng with HEstation is c on str uc te d, it c an s up ply water to so meo f the existin g irrigated area in N ag arju na S agarcom mand. This w ould.facilitate to extend theNagarjuna Sagar Right Bank Canal up toS om asila reserv oir in P enn ar 'riv er basin brin g-in g a dd itio na l a re a u nd er irrig atio n a nd to trans-fer K rish na w ater to Pcnnar river basin for itsir rig atio n r eq uir eme nts . Wh e n th is carry forwardstorage w ater is used in the dow nstream irriga-t ion requ i rements , the wa te r a va il ab le u pst re amin Srisailam reservoir can be used f or c re at ingadditional irrigated area under Telugu G anga.Galcru-Nagari, Velugodu, H indri Neeva,S risailarn L eft B an k Canal, e tc . s ch eme s. It isconsidered that 30% , 20% and 50% of the 31 8TM C of carry forw ard storage w ater is used fo rirrigation in K rishna D elta, Pulichintala com -mand and Nagarjuna Sagar com mand respec-tively. Nearly 210 meters,180 meters and 90m eters h yd ra ulic h ead s are av ailab le in th e down-

stream H E station s for po wer generation b efo re u sing fo rirrig atio n fro m K rish na B arra ge , P ulich in taIa rese rv oiran d N ag arju na S ag ar re serv oir re sp ec tiv ely . T he a ve rag ehead available is 144 m eters (210 x 0.3 + 180 x 0.2 +90 x 0.5) for pow er generation before using for irriga-tion during good m onsoon years.

WATER MANAGEMEfIITIt is envisaged that the w ater stored in the PSS is let into

d ow nstrea m re se rv oirs (S risa ila m an d N ag arju na S ag ar) be-fore the end of every m onsoon year. These dow nstream res-erv oirs b ein g p artially e mp ty d urin g th e la ter h alf o f m on so onyear, retain the w ater as carry forward storage for the nextm onso on year. T his w ill facilitate to g en erate po wee fro m th estored water in the PSS during summer months when thepow er/energy shortage is m ore acute and dow nstream H Estations arc not in operation due to lack of w ater.

W h en w ater availability in the d ow nstream (S risailam ,N agarjuna Sagar, etc.) reservoirs is sufficient during good

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m onsoon years, w ater requirem ent for all the irrigation sys- w at er i n the P SS during good m onsoon years is used ascarryt erns can be m et from the dow nstream reservoirs itself w ith- fo rw ard sto rag e for n ex t y ea r. "out depending on the water stored in the PSS. T he stored

TABLB 3 EcoNOMIC ANALYSts Of' PUMPEDSTORAGeSOIHMII (Cxsa-I)Average Pumped storage GroSi power Energy Revenue Economicallyhead of scheme capacity generation generation (Rs. crores p e r year) affordablepumped (MW) capacity' (million kWh) invaIrnemstorage (MW) withscheme, downstream Rereres(meters) Pump Turbine head Groll Consumption l\'CI Energy Energy Net R /MW (IUI-

mode mode (1934 MW) generation (pump mode) general ion sales purchases revenue crores bine mode)30 406 294 ,2228 2406 438 1968 122 31 691 3455 11.7540 542 391 2325 2511 585 1926 753 41 712 3560 9.1050 671 489 2423 2617 731 18~6 785 51 734 3670 7.5160 813 587 2521 2723 878 1845 817 61 756 3780 6.4470 948 685 2619 2829 1024 1805 849 72 777 3885 5.67

2'117 2934 1171 1763 880 82 798 . 3990 5.100 1084 78390 1219 881 2 8 1 5 3040 1317 1723 912 92 820 4100 4 . 6 5100 1 3 5 4 979 2913 3146 1462 1684 944 102 842 4210 4.30110 1490 1076 3010 3251 1609 1642 975 113 862 4310 4.01

SOles:Overall effeciency in turbine mode and pwnp mode is 85% each. Average pumping and generating hOUR each are 1080 houn in a year foreconomic analysis.

2. Energy purchase price is II RI 0.70 per kWh during good monsoon yean. Energy sale price i. at RI.3.0 per kWh.3. Financial COIl (inlcresl on loan capiLal, return on equilY capital and depreciation) is 19% of PSS oost. O~ OOCI of PSS U I~ of illCOIL4. The affordable investment also includes rehabilitation compensation. interest during construction. price escalation durin, conauvction, etc.

TABle 4 EcoNOMIC ANALYSISOf' PUMPED STOItACESOtEME (CASH-n)Average Pumped slOnlge Groupower Energy Revenue Economicallyhead of schane capacity generalion generation (RI. CtOI'CI pe r year) affordablepumped (MW) capacity (million kWh) in~cnlstorage (MW)with "-:scheme, dowrutn:am R . s . C I ' O I ' C I(meters) Pump Turbine head Gross Conswnpt ion Ncs Energy Energy Net R.. fMW(wr-

mode mode (1326 MW) generation (purnpmodc) gmeration sales pu~es revenue cron:s binemode)30 " 40 6 294 1620 1750 438 1312 S 2 5 31 494 2470 8.4040 542 391 1717 1854 5 8 5 1269 556 41 5 1 5 2S75 6.5950 677 489 1 8 1 S 1960 731 1229 5 8 8 5 1 5 3 7 2685 5.4960 813 587 1913 2066 878 1188 620 61 559 2795 4.7670 948 685 2011 2172 1024 1148 637 72 5 6 S 2825 4.1280 1084 783 2109 2278 1171 1107 683 82 601 3005 3.8490 1219 881 2207 2384 1317 1067 7 1 5 92 623 3115 3.54100 1354 979 2305 2489 1462 1027 747 102 645 3225 3.29110 1490 1076 2402 2594 1609 985 778 113 66 S 3325 3.09

Notes:Overall cffecieney in turbine mode and pump mode is 85% each. Average pumping and generating hours each are 1080 hours in a year foreconomic analysis.

2. Energy purchase price is at Rs. 0.70 per kWh during good monsoon years. Energy sale price is II Rs.3.0 per kWh.3. Financial cost (interest on loan capital. return on equhy capital and depreciation) is 19% of PSS cost. O&M COSI of PSS i.1% of ill COIL.4. The afrordable investment also includes rehabilitation, compensation, interest during construction, price escalation during constructien, ClC.

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The following possibilities are examined for planning us-age of water with the help of PSS :I. Bad monsoon succeeds good monsoon (GB): The carry

forward storage in the downstream reservoirs w ill be uti-lised for early crop up to middle of July month in thecommand areas of Krishna Barrage. Pulichintala andNagarjuna Sagar. The fresh inflow into downstream res-crvoirs from later h alf o f Ju ly month, will be used for restof irrigation needs of these areas and irrigation needs ofSrisailam command area. In this case entire irrigationneeds are met and creation of carry forward storage forIl C.X ty ea r i s not p ossib le d ue [0 bad monsoon year.

') Good monsoon succeeds bad monsoon (BG): Since thecarry forward storage could not be maintained in the pre-\IOUS year. there is no water available to start sowingactivity with the onset of monsoon. W ater w ill be sup-plied to the entire irrigated area under all reservoirs from15th July when the inflow into the reservoirs is adequatefor irrigation needs. Being a good monsoon, surplus wa-ter is available to pump into the PSS to create carry for-ward storage for next year. Pumping operation of PSS isdone with the secondary power available from the HEstations during m onsoon season.

3. Bad monsoon succeeds bad monsoon (8B): In this casesufficient w ater is not available in the river due to badmonsoon and absenee of carry forward storage from pre-vious year. Priority is given to supply water to the oldirrigation system s due to insufficient water avai labt lr t yand pumping operation also can not be done for crcnungcarry forward storage. TIle probability of two successivebad monsoons is once in four years when bad monsoonoccurrence is once in two years.

4 Good monsoon succeeds good monsoon (GG): The carryforward storage in the downstream reservoirs is used fore:uly crop up to middle of July in the command areas of,~Jgarjuna Sagar, Pulichintala and Krishna Barrage. Thefresh inflow after 15th July into the dow nstream reser-voirs during the good monsoon will be used for the restof irrigation needs of these areas and irrigation needs ofSrisailarn command area. W hen flood water is available.water is pumped into the PSS by consuming secondarypow er from HE stations to create carry forward storagefor next year.As explained above. the dependability of water for newly

irrigated areas due to the PSS. is three years out of four yearswhich is 75% dependability. W ater availability is not possi-ble from second bad monsoon year when bad monsoons oc-cur successively. The benefits of PSS during variouscombinations of monsoon behaviour (good or bad) is shownin Table 2. PSS facilitates to harness the water for irrigationtwice its storage capacity (upper reservoir) during goodmonsoon years by creating carry forward storage for nextyear.72

E conom ic analysisAverage pumping/generating hours of PSS: The PSS wouldbe in operation when water availability in the river is nearlyat 50% dependability. During good monsoon year, the PSSpumps water for 90 days (2160 hours). The probability ofgood monsoon at 50% dependable yield is once in tw o years.So the operating hours of PSS both in pumping mode andturbine mode arc considered as 1080 hours/year each foreconomic a na ly sis p urpos e.

Power purchase price: During good monsoons, unex-peered cheap secondary power from the HE stations is avail-able. If U lC power demand could not consume the availablesecondary power from the HE stations. few thermal powerSl:IllOIlS need to be taken out of operation. Pumping opera-tilHl of ! 'SS would consume this secondary power facilitat-IIlh! thermal pow er stations keep operating. The in crem en ta lL ll~t for enhanced power generation by the thermal stationsIS Il~ fuel cost only. So the power purchase price of PSS isconsidered as Rs. 0.70 per kW h which is 'average fuel costo f th erm al statio n.Power sale price: The generation cost of latest thermalrower stations which arc meant for catering to base load, isnearly Rs. 2.5 per kW h. Moreover the hydro power gcncr-atcd due to PSS is peaking power which canmcct daily peakdemands as well as seasonal energy shortages. So the saleprice of power generated due to PSS is considered as Rs. 3p er kWh.

TIle following are the major features of a PSS which In-Ilucnccs its installation cosl/MW :I. Hydraulic head of the turbines: If head of turbines in-

creases, UIC equipment cost per M W decreases.2. Height of darn: If the dam height is more. its cost in-

creases.3 . Submergence area of reservoir: If the submergence area

IS more due to shallow storage capacity. the cost of landacq uisitio n, co mp en satio n an d reh ab ilitatio n expenditureincreases.So it is not possible to estimate the cost of the PSS with-

out site specific data. In the absence of site specific data, anattem pt is m ade to lind the economically affordable invest-m ent per r v [ w (turbine mode) for various average hydraulicheads of P5S.

The following paucrn of using the stored water in the PSSis considered for econom ic analysis:

Case I : T he stored water (318 TMC) is entirely used forpower generation during good monsoon years which takeplace one out of two (50%) years. So 210 meters total hy-draulic head is available in the downstream of PSS which isequal to 1934 MW power generation capacity. From the eco-nomic analysis shown in Table 3, the econmically affordablecost per MW (Rs. 4.0Icrores/MW ) of PSS is very favour-able up to 110 meters average hydraulic head.

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re'-is)-Ier -

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Case II : The carry forw ard storage w ater (318 TM C) isused for power generation in the downstream H E stations.b efore u sin g for irrig ation n eeds. T he availab le head in the

. d ow nstream ofP SS is 1 44 m eters w hich is equa l to 1326 M Wpow er generation capacity. From the econom ic analysisshow n in Table 4, the econom ically affordable cost per M W(Rs. 354 crorcs/M W ) of PSS is very favourable up to 90 m e-t er s a ve ra ge hyd rauli c h ead. If the stored water is to be usedfor irrigatio n fin ally as exp lained an d th e averag e h yd raulichead of the PSS is less than 90 m eters, the PSS is econom i-cally viable by the revenue from its pow er generation alonew ith ou t exp ecting any rev en ue fro m irrig ation u sage.

O ther beneficial features of PS S: The dam ' of the P SS canbe non overflow type w ithout any spillw ay because the peakflood flows from its catchm ent area is fraction of the stor-age reservo ir capacity en visaged , T he h yd ro tu rbin es o f P SSc an ea sily h an dle th e flood w ater to pass dow nstream in caseit is necessary. This feature tends-to reduce the cost of PS S.

The dead storage of the reservoir created by PSS can benom inal since the inflow s carrying silt from its catchm entarea is negligible. This feature is one of the factors to m ax-im ise th e liv e sto rage capacity o f P SS .

Transfer of Godavari river water to Krishna riverGodavar i r iv er h a s substantial water flow from July to N o-vember and negligible now in rest of months. Typicalhydrograph of the river during m onsoon season is show n inF ig. 2. This necessitates to construct storage reservoirs ont he r iv er 1 0 utilise w ater during lean flow period for irriga-tion needs in its basin and to transfer to river K rishna. A Iready our irrigation planners have proposed to transferGod av ar i w ate r to K rish na riv er b y id en tif yin g multi p urp osedam s at lncham pally and Polavaram as diversion points,T he se a rc in ter sta te p ro je cts whic h wou ld su bmerg e v ast ar eaof th ick reserv e fo rests and necessitate reh abilitation of ef-f ec te d trib al p op ula tio n p osin g d iffic ulty in g ettin g en viro n-m ent c1~ces. It is required to reduce the proposed storagec ap acitie s d ras tic ally to m in im ise in te rsta te. fo re st su bmer -gen ce and tribal po pu lation reh abilitatio n p rob lem s. Th esereduced storage capacities w ould be sufficient' only to th ewate r re qu ireme nts o f id en tifie d irr ig atio n sc hemes d ire ctlyunder these reservoirs leaving no scope to transfer w ater toK rishn a riv er du ring lean flo w p eriod .

G odavari river flood w ater can be diverted to K rishnariver d urin g monsoo n months by g ravity to K rishn a B arrag ean d P ulichintala reservo ir to m ak e up sh ortage of w ater d ur-ing bad m onsoons. This can be achieved without any stor-ag e r ese rv oir s o n God av ari r iv er fo r th is p ur po se . T his wou ldfacilitate to create carry forw ard sto rag e by p umping w ateravailable in the upstream of river at Srisailam reservoirinto P SS even during bad m onsoons. Thus the dependabil-ity of w ater fo r v ario us requ irem ents fro m K rishn a riv er canbe enhanced to 100% u ltimate ly b y tr an sfe rr in g God av ar i w a-IN DIA N IO U R.." AL O F roWE R & R IV ER VA UE Y D EV EL OPM EN T

. . . : i f . > j ~ ;tcr to K rishna during m onsoon m onths only. In this w ay, the.~.;Lsto rag e cap acity o f the P SS ob viates to som e ex tent th e n~:'~~>'"o f s to ra ge r es ervo ir s on Godava ri to t rans fe r wafe r to K r i s h D 8 i F ' .

~:; .1riverConclusion

E nv isaging few pu mp ed storag e schem es to harness th e 5 0%dependable w ater in the river K rishna is econom ically vi-able by the revenue from its pow er generation alone w ithoutex pectin g an y revenu e from itrig ation usag e. 1be PSS hashigh flexibility to m eet any or com bination of th e followingneeds:Power genera tion :1. Pow er generation to m eet daily peak dem and.2. P ow er generation to m eet seasonal (sum mer) shortages.3. To store the surplus power in the grid and supply to grid

during shortage. ...4. To consum e the surplus pow er available injbe g rid d ur-

in g go od mon so on season s.I rr ig a ti on u s es :I. To convert 50% dep end ab le yield in to 75% dependable

y ie ld fo r cr ea tin g n ew ir rig atio n fa cilitie s.2 To supply additional water to th e existing irrigatio n fa-

cilities.3. To m aintain optim um w ater levels in downstr eam res er -

v oirs fo r fe ed in g v ar io us irr ig atio n canals fo r Io og er d u-ration.

4. To m atch the cropping/sow ing activity w ith the onset ofmonsoon by ma in ta in ing carry forward s to rage .

5. T o act as su bstitu te 1 0 the balancing reservoirs of new ir-r ig at ion s cheme s and s to ra ge r es ervo ir s 00Godavar i riveralso.W ater uses from the PSS can also be altered in future to

match th e chan ging needs. T he w ater available betw een 50 %and 75% dependable yield in the river can be harnessed ec0-n om ic ally fo r c re atin g n ew ir rig atio n fa cilitie s w ith a ssu re dwater availability for three (3) out of four (4) years by en-v isa gin g few PSS .

The w ater. dem and from the K rishna river s u r p a s s e s thew ater available in the river. A lready, m ost of th e reliablew ater in the river.h as been harnessed. The next step wouldb e to h arn ess the u nreliab le w ater av ailable in th e river. Thiscan be achieved cconom ically by envisaging few pum peds to ra ge sc heme s lo ca te d u pstre am o f th e e x.is tin g re ser vo irs.U l tima te ly Godava ri wat er c an be t ra ns fe rr ed t o Krishna riverf or f ur th er s ta bil is at ion o f i rr ig ati on in K rish na an d P en narr iver basins .

References1. R ao K .L ., India's w ater w ealth.2. Interbasin tr an sfe r o f w ate r, URJA, D ecember 19 91 .

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