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Springs in a headwater basin in the Deccan Trap country of the Western Ghats,

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DOI: 10.1007/s10040-002-0213-9

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Hydrogeology Journal (2002) 10:553–565 DOI 10.1007/s10040-002-0213-9

Abstract Available literature reveals that little work hasbeen done on the origin of springs in a basaltic terrain.Close examination of such springs in about 2,000 km2 ofthe upper Koyna River basin in the Deccan Trap countryof the Western Ghats (hills), India, reveals that their ori-gins are dependent on the lithologic character of differ-ent basaltic flow units and the existing physiography. Al-though rainfall, its seasonality and areas of recharge,play vital roles in the recharge of these springs, theiryields are also controlled by lithological variations andhydraulic characteristics of their source-aquifers. Chemi-cal concentrations of these springs are heavily dependenton the lithological compositions of the source-aquifersand the residence time of groundwater in these aquifers.Currently, basaltic springs are classified with those issu-ing from other terrains. However, because the emergenceof groundwater in the form of springs is largely con-trolled by the lithology and the resulting water-bearingproperties of the formations, a new classification schemeis proposed that classifies the springs on the basis oftheir source-aquifers.

While tapping springs for drinking/irrigation purpos-es, it must be remembered that they also sustain thou-sands of other life forms vital to a balanced ecosystem.Changes in the uses of these springs may also affect oth-er human communities downstream. Therefore, beforedeveloping spring flow, a trade-off must be made consid-ering local needs and downstream users. Emphasizingonly local human needs may lead to severe intercommu-nity conflict and negative environmental consequences.

Résumé Une recherche bibliographique montre qu’ilexiste peu de travaux sur l’origine des sources en terrainbasaltique. Un examen détaillé de telles sources sur envi-ron 2,000 km2 dans le bassin de la rivière Koyna, dans larégion des traps du Dekkan des Ghats (collines) del’ouest (Inde), montre que leur origine dépend de la lit-hologie des différentes unités de coulées basaltiques etde la physiographie actuelle. Bien que la pluie, sa sai-sonnalité et les zones de recharge jouent un rôle essentieldans l’alimentation de ces sources, leur débit est aussicontrôlé par les variations lithologiques et les caractéris-tiques hydrauliques des aquifères qu’elles drainent. Lacomposition chimique de leurs eaux dépend très forte-ment de la composition lithologique des formationsaquifères drainées et du temps de séjour de l’eau souter-raine. Habituellement, les sources des basaltes sont clas-sées avec celles issues d’autres terrains. Toutefois, com-me l’émergence de l’eau souterraine à une source est for-tement contrôlée par la lithologie et les propriétés aquif-ères résultantes des formations, un nouveau modèle declassification est proposé pour classer les sources à partirdes aquifères drainés.

Alors que l’on capte les sources pour l’eau potable oul’irrigation, il faut garder en mémoire le fait qu’elles sontaussi l’élément vital pour des milliers d’autres formes devie dans un écosystème équilibré. Des modifications desusages de ces sources peuvent affecter également d’au-tres communautés humaines en aval. C’est pourquoi,avant de mettre en exploitation une source, un accorddoit être mis en place pour prendre en considération lesbesoins locaux et les usagers de l’aval. Le fait de mettrel’accent uniquement sur les besoins humains locaux peutconduire à des conflits graves entre les communautés età des conséquences négatives sur l’environnement.

Resumen No abundan las referencias bibliográficas re-lacionadas con el origen de manantiales en rocas basálti-cas. El estudio detallado de este tipo de manantiales enun área de unos 2,000 km2 de la cuenca alta del RíoKoyna, en Deccan Trap (Ghats Occidentales, India), re-vela que sus orígenes dependen de la litología de dife-rentes unidades de flujo basáltico y de la fisiografía exi-stente. Aunque la precipitación, su estacionalidad y laszonas de recarga desempeñan un papel vital en la recargade dichos manantiales, sus caudales también están con-

Received: 4 May 2001 / Accepted: 22 May 2002Published online: 31 July 2002

© Springer-Verlag 2002

P.K. Naik (✉)Central Ground Water Board, Central Region, New Secretariat Building, Civil Lines, Nagpur 440001, Indiae-mail: pnaikus@yahoo.comTel.: +91-712-512400, Fax: +91-712-534391

A.K. Awasthi · P.C. MohanDepartment of Earth Sciences, Indian Institute of Technology,Roorkee 247667, India

Springs in a headwater basin in the Deccan Trap country of the Western Ghats, IndiaPradeep K. Naik · Arun K. AwasthiPrakash C. Mohan

trolados por las variaciones litológicas y las característi-cas hidráulicas de los acuíferos base. Las concentracio-nes de diversos parámetros químicos en estos manantia-les dependen enormemente de la composición litológicade sus acuíferos, y del tiempo de residencia de las aguassubterráneas. Actualmente, se clasifica los manantialesbasálticos junto con otros situados en materiales distin-tos. Sin embargo, la gran influencia de la litología endichos manantiales, así como los efectos en las propieda-des de las formaciones acuíferas que los alumbran, hanllevado a la propuesta de una nueva clasificación quetenga en cuenta los acuíferos de los que se originan.

Cuando se aprovecha manantiales para producir aguapotable o para riego, se debe recordar que también sosti-enen miles de formas de vida diferentes, que son vitalespara mantener un ecosistema equilibrado. Los cambiosen la utilización de estos manantiales pueden afectartambién a otros usuarios situados aguas abajo. Por tanto,hay que establecer un balance entre las necesidades loca-les y las de otros usuarios del sistema antes de decidirutilizar los recursos proporcionados por los manantiales.Enfatizar únicamente en las necesidades locales puedeacarrear graves conflictos entre comunidades e impactosmedioambientales negativos.

Keywords Deccan trap · Groundwater development ·Hydrochemistry · Springs · Western Ghats

Introduction

All recharge to groundwater discharges naturally and canbe used by a wide variety of organisms, including (butnot limited to) mankind, in the special ecosystem thatthey sustain. Springs are natural outlets through whichgroundwater emerges at the ground surface as concen-trated discharge from an aquifer and are one of the mostconspicuous forms of natural return of groundwater tothe surface. As spring waters flow down a slope, a por-tion of the flow may seep into the ground, adding to therecharge of the lower aquifers. In the long history ofmankind, these great resources have often been de-stroyed by diversion or ‘development’ in short-sightedattempts to improve water supplies for human communi-ties. This frequently has had adverse effects on the envi-rons of the original springs and seeps. Springs in thehigh hills of the Western Ghats (hills), in the westernmargin of the Indian Peninsula, are no exception. Theysustain the life of thousands of human beings, plants, an-imals, birds and other organisms. In the name of devel-opment, these springs are under constant exploitation forlocal water supply. Their natural settings and sources areoften modified, thus diminishing their life and oftencausing their complete disappearance.

An attempt has been made to study these springs ofthe Western Ghats area and to classify them with respectto their origin, distribution, discharge and quality forpossible use as a potable source of water. A total of 121springs have been investigated at or very close to their

origins in the Koyna River basin, a ‘head water’ basin inthe Deccan Trap country of the Western Ghats, in an areaof 2,036 km2. Locations are shown in Fig. 1. The KoynaRiver basin has an elevation of 550–1,460 m above sealevel (a.s.l.) and represents a typical physiographical set-ting characteristic of the Deccan Plateau. Naik et al.(2001) give a detailed account of this river basin and itshydrogeological framework.

Geologically, the Koyna River basin consists of basal-tic lava flows that erupted through fissures during thelate Cretaceous to lower Eocene time. Commonly, theseflows are lateritized at their tops, especially at higher locations and wetter conditions. Alluvium of the riverKoyna is localized in the valley section. Each basalticflow consists of two main trap units: (1) a lower massiveunit and (2) an upper vesicular unit. The massive unitconstitutes the main trap unit and forms 60–85% of thebasaltic flows. These are mostly fine-grained, dense,compact and greenish to dark grey in colour. They occa-sionally exhibit columnar and spheroidal structures andoften show well-developed multi-dimensional joints. Thevesicular unit forms the upper horizon of each flow andconstitutes 15–40% of the individual basaltic flows.They are generally soft, fine grained and greenish tobrownish in colour. The vesicles are rounded to oval-shaped and are either open and interconnected or filledwith secondary minerals, such as zeolite, quartz and cal-cite. When they are filled with secondary minerals, thevesicular basalt is called the amygdaloidal basalt. Be-cause of weathering, the secondary minerals are removedfrom exposed rock surfaces, leaving a pitted appearance.Generally, the consecutive lava flows are separated by ared layer, varying in thickness from 0.20–1.30 m. Terms,such as red bed (Kanegaonkar 1977), redbole (Gupte1979) and red tuffaceous material in the interflow zone(Kshirasagar 1981) have been used to describe this redlayer. ‘Redbole’, however, is the commonly acceptedterm. Redboles are considered to be in-situ products ofweathering (laterization) during a long time gap after theearlier flow (CGWB 1984), and are subsequently bakedby the succeeding flow.

Climate

The Koyna River basin experiences a subtropical mon-soon type of climate. The Indian monsoon, the most hy-drologically significant of India’s three seasons, lastsfrom June–September and brings about 88% of the annu-al rainfall. The winter season is from November–Febru-ary and the summer extends from March–May. The win-ter season brings about 8% of the annual rainfall and thesummer about 4%. There is a systematic variation in thedistribution of rainfall in the area because of the oro-graphic influence of the Western Ghats. The annual rain-fall decreases steadily from the western to the eastern ar-eas. Highest annual average rainfall is recorded at Maha-baleswar (6,024 mm) in the north whereas the lowest isreceived at Karad (745 mm) in the east. January is the

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coldest month and daily mean monthly minimum tem-perature ranges from 10–14 °C. May is the hottestmonth, the daily mean monthly maximum temperaturevarying between 31–37 °C. The air is highly humid dur-ing the monsoon months. The relative humidity rangesfrom 79–96% in the morning (830 h) and 70–100% inthe evening (1,730 h) during this period. March has thelowest humidity of 31–43%. The dryness is moremarked in the plains than in the upland regions.

Origin of Springs

Conditions necessary to produce springs are many andare related to different combinations of geologic, hydro-logic, hydraulic, pedological, climatic and even biologiccontrols (Maxey 1964). In the Western Ghats, the geo-logic control, particularly the physiographic/geomorphicsetting, is the most important factor in the origin ofsprings. Most of the hills in the Western Ghats are flat-topped, although some tops are very narrow, but stillprovide evidence of a broad flat plateau prior to dissec-tion by the Koyna River and other streams. Characteristi-

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Fig. 1 Location of spring sampling locations and eleva-tions in the upper Koyna River basin, India

cally, at elevations lower than flat hilltops, on both sidesof the hills, there exist hill terraces, giving a step-like ap-pearance in an aerial view. Such hill terraces generallyare developed in relatively massive basalts, but, becauseof constant weathering, they are leached, and often are inthe process of lateritization or are completely lateritized.Commonly, hilltops in the area above a height of 975 ma.s.l. are lateritized.

Geological Controls of Groundwater Movementand Location of SpringsThe numerous streams in the hilly tracts of the WesternGhats generally start with springs that carve narrow gul-lies on hill faces. Such narrow gullies gradually grow insize exposing the source aquifer from which groundwa-ter oozes from a number of points above the less perme-able basaltic unit. Groups of these springs contribute sig-nificantly to streamflow. When a stream travels for along distance at high elevation over a gentle slope, thestreamflow is strengthened by the contribution from sev-eral such points along its flow path. Such contributionsof groundwater create a significant base flow, and manyof these streams are perennial.

The preferred flow paths of groundwater convergingon springs are determined by the interconnected porespaces, especially fractures, existing in the rock units,generally resting on rocks of low permeability, for exam-ple, at the contact between the vesicular unit and mas-sive unit or highly weathered massive unit and relativelypoorly weathered (or unweathered) flow unit. The fol-lowing geologic conditions control the occurrence ofsprings in the study area. Many of these conditions arediagrammatically shown in Fig. 2.

1. If the source-aquifer is in laterite, rainwater in it per-colates very rapidly because of high permeability ofthe rock. However, the downward movement of wateris blocked by a lithomargic clay that commonly existsat the base of the laterite. Groundwater emerges as aspring where the lithomargic clay outcrops. A litho-marge is a smooth, indurated variety of common kao-

lin, consisting at least in part of a mixture of kaoliniteand halloysite (Bates and Jackson 1987). Sometimes alithomargic clay horizon is non-existent at the bottom,and the spring emerges at the contact between thelaterite and the poorly lateritized basaltic flow. Ninepercent of the springs examined at their source havethis type of origin.

2. If the source-aquifer is a vesicular basalt, springsooze out at the contact between the vesicular basaltabove and the non-vesicular basalt below (which maybe weathered or massive). Twenty percent of thesprings investigated have this type of occurrence, i.e.they emerge at the contact between the vesicular ba-salt and weathered massive basalt or relatively hardmassive basalt.

3. Generally, the entire thickness of the massive basalticunit underlying hilltops and/or hill terraces is weath-ered; however, the degree of weathering gradually de-creases with depth. Thus, the highly weathered basaltgrades into the less weathered basalt of the same flowunit and two hydraulically different layers are formed.Percolating rainwater gets blocked at the poorlyweathered massive basalt and oozes out as springs inhill slopes or gullies in the slopes. Twenty percent ofthe springs examined are found at the contact betweenthe weathered massive basalt and moderately weath-ered massive basalt or hard massive basalt.

4. When the entire thickness of a basaltic flow in a hillterrace is well-weathered, rain water percolates easilythroughout the entire thickness; however, these unitsare often underlain by thick slightly permeable red-bole beds, which deflect the water laterally to springsthat emerge on the hillside at the outcrops of the red-bole bed. Seventeen percent of springs were found tobelong to this category. However, if the redbole is toothin to inhibit the downward movement of water or isabsent (this rarely happens at higher elevations inyounger flows), groundwater percolates further down-ward until it is blocked by a relatively impermeablestratum to emerge as springs.

5. Talus deposits are very common and widespread athigher elevations. Thick piles of broken pieces of

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Fig. 2 Cross sections in the up-per Koyna River basin, India,showing the geologic settingsof several types of springs

rocks and weathered materials are found on hillslopes. The narrow ridges on hilltops are remnants oferosion, the eroded materials or talus occur in piles ad-jacent to the hill terraces. The talus deposits are quitepermeable because they are unconsolidated. Watervery easily seeps into the talus deposits and emergesas springs when the downward movement of water isblocked by less permeable underlying rock. Twenty-three percent of the springs were found at the contactbetween the talus deposits and less permeable strata.

6. Springs oozing out of fractures/joints also occur in theWestern Ghats. Closely spaced horizontal to subhori-zontal joints (or sheet joints) are often found near thetop of individual flow layers at intervals of 0.2–2 m.Vertical joints, which are prominent in many of themassive flows, do not extend into either the vesicu-lar/fragmentary top of the flow or into underlyingflows. Horizontal joints mostly form seepage zonesrather than distinct springs in stream channels. In thesummer, the springs that occur in horizontal joints arecommonly reported to be dry, whereas the springsemerging from vertical joints are reported as havingsome discharge. It may be because the existing piezo-metric heads, which cause the upward movement ofgroundwater through such joints, are low in summerbecause of limited recharge. Eleven percent of thesprings studied are of this type.

The basaltic flows generally are nearly horizontal with aneastward dip of about 6–8° (Pitale at al. 1987). Despitethe fact that they have lateral variations, the lithologicand hydraulic characteristics are more or less similarwithin a few kilometres. A number of springs mayemerge from a particular flow at several points and mayalign along a line within a few kilometres (Fig. 2). Again,springs emerge on both sides of a water-divide because ofexposure of the rock formation on either side of the di-vide. However, springs issuing from a point at one sidemay not exist exactly at the same level on the oppositeside. Thus, lithology, structure and interflow processes allhave a role in the locations of emergence of springs.

To summarize, springs generally issue at the contactsbetween laterite and lithomargic clay or poorly lateriti-zed basaltic flow, vesicular basalt and non-vesicularmassive basalt, highly weathered massive basalt andmoderately or poorly weathered massive basalt or red-bole, and/or talus deposits and hard massive basalt orlaterite or lateritized basaltic flow. Springs also emergefrom fractures, both horizontal and vertical, in each ofthe geologic units and from the intersections of fractureswith different orientations.

Distribution of Springs by Elevation and their Recharge Areas

Springs generally are distributed at an elevation range of600–1,340 m a.s.l. in the upper Koyna River basin(Fig. 1). Table 1 gives the percentage distribution of

these springs in different elevations. The highest springlocation was found at an altitude of 1,340 m a.s.l. at OldMahabaleshwar. The area of the Koyna River Basinabove the elevation of 1,100 m is very small; therefore,only a very small percentage (9%) of springs occurabove this altitude. A distinct 20-m-thick laterite rockcliff is found at approximately 1,060–1,080 m elevationthat extends from the eastern side of the basin to the cen-tral part. Above this elevation are extensive tablelands,which serve as recharge areas for the springs located be-low the rock cliff. Of the 121 springs examined, 13% oc-cur at the elevation range of 1,000–1,100 m a.s.l. In thesouthern part of the Koyna River Basin, a distinct breakin slope occurs at the 900-m contour. Hill slopes becomesteeper below this contour. Above 900 m, the area as awhole is generally level to gently rolling. Hill terracesare extensive. Rocks show lateritization above an alti-tude of 975 m. Talus deposits form considerable thick-ness. Similar conditions occur in the central part of thebasin, but the hill terraces are above 950 m altitude.Thus, nearly half of the springs (47%) occur at an eleva-tion range of 900–1,000 m. Whereas groundwater with-drawal through dug wells and bored wells in the area isconcentrated at the elevation range of 550–700 m a.s.l.,springs on the hill slopes emerge at an elevation of about650 m a.s.l. and form an additional source of water forthe inhabitants in the foothill zones where the successrate of dug wells and bore wells is meagre. About 11%of the 121 springs examined were found to occur be-tween 650–700 m a.s.l.

One characteristic feature observed during field in-vestigation is that the western part of the main ridge ofthe Western Ghats (Koyna River basin is on the easternpart of the main ridge) facing the Coastal Tracts (Arabi-an Sea) has very few springs, mostly of an ephemeral na-ture. This area experiences the same subtropical mon-soon type of climate as the Koyna River basin with ayearly average rainfall of about 4,000–5,000 mm. Tem-perature variation is also similar to that of the KoynaRiver basin. However, physiographically the westernpart is steeper in slope and forms a N–S-trending escarp-ment. Hardly a hill terrace is found to form any potentialzone for formation of springs. The 6–8° eastward dip ofthe basaltic flows (Pitale et al. 1987) also contribute sig-nificantly to the concentration of the springs on the east-

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Table 1 Elevation distributionof springs Elevation No. of % of

range springs springs(m a.s.l.)

600–700 13 11700–800 12 10800–900 12 10900–1,000 57 47

1,000–1,100 16 131,100–1,200 4 31,200–1,300 2 21,300–1,400 5 4

Total 121 100

ern side. Along the base of the N–S-trending escarpmentin the western part, at an elevation of about 10–20 ma.s.l., there is a series of hot springs situated in a lineparallel to the Indian West Coast. Pitale et al. (1987)have done extensive studies on this hot springs belt. Thelinear disposition of the hot springs is a prominent fea-ture and may be indicative of a deep-seated fault (Gupte1968).

Although springs occur at an elevation range of600–1,350 m a.s.l. in the upper Koyna River Basin, theirmain concentration is in the rolling hilltops and flat areasrather than on the steep slopes. In fact, these slopes hard-

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Hydrogeology Journal (2002) 10:553–565 DOI 10.1007/s10040-002-0213-9

Fig. 3 Map showing spring re-charge areas and other surfacefeatures in the upper KoynaRiver basin, India

ly allow rainwater to percolate downward to form poten-tial springs and, hence, do not form recharge areas.Therefore, these steep slope areas have been demarcatedand their areal extent has been calculated with the helpof a planimeter. Similarly, the areas that form potentialzones for spring formation have been demarcated (Table 2). These features are shown in Fig. 3.

Thus, about 35% of the total area of the Koyna Riverbasin forms recharge areas that support springs. In thecentral part of the river basin, in an area of 80 km2 ofspring recharge area, there were 70–80 springs; thus, theaverage distribution of springs in the area is about one

large discharges, a 90° V-notch weir was used to mea-sure spring flow. Discharge of the 74 springs variedbetween 0.024 l/s (86 l/h or 2.06 m3/day) and 5 l/s(18,000 l/h or 432 m3/day) in the winter (Decem-ber–February). The mean winter discharge of the indi-vidual springs is estimated at 46 m3/day. No measure-ments were made in the spring season. The summer dis-charges varied between 0.011 l/s (39 l/h or 0.94 m3/day)and 2.5 l/s (9,000 l/h or 216 m3/day). The mean summerdischarge of the individual springs is estimated to be28 m3/day. The summer discharges were measured in aspan of 15 days during May. Spring discharges peak dur-ing the monsoon season (June–September), as reportedby the local inhabitants, resulting from peaks in re-charge. However, no measurement could be made duringthe monsoon period.

Discharge vs. Elevation and Other FactorsMeinzer (1923) classified springs based on their magni-tude of discharge. Table 3 shows a modified version of Meinzer’s (1923) classification, and Table 4 shows the discharge ranges of springs examined and the corresponding Meinzer’s (1923) magnitude. Based onMeinzer’s (1923) classification, springs of the magnitude5th and 6th are prevalent in the Koyna River basin. Dis-tribution of these spring discharges in different eleva-tions is shown in Table 5.

The discharge of a spring depends upon the area thatcontributes recharge to the aquifer and the rate of re-charge (Bowen 1982). It also depends on lithological andhydraulic characteristics of the aquifers. In the KoynaRiver basin, between an elevation of 1,400–1,300 ma.s.l., the aquifers are mostly talus deposits. Talus depos-its in the area naturally are highly porous and permeableand have an average transmissivity of 128 m2/day asagainst an average of 67 m2/day in basalts (Naik et al.2001). Because of the talus and rolling nature of the hillranges at this elevation, the recharge received by theseaquifers is high and the resulting springs, although fewin numbers, have high discharges (>72 m3/day). The ele-vation range of 900–1,000 m has the maximum numberof springs (47%) in the area. These springs issue fromlaterites, talus deposits, vesicular basalts and weatheredmassive basalts and have a range of spring dischargesvarying between 2–12 to >72 m3/day. However, theprobability of occurrence of high yielding springs(>72 m3/day) at this elevation range is only 18% asagainst 50% at the elevation range of 1,300–1,400 m.

Classification of Springs

There are various types of spring flow domains depend-ing on aquifer geometry and other physical factors. Nu-merous specific descriptive terms for springs have devel-oped, but no single basis of classification satisfies theneed of general usage. Maxey (1964) and Alfaro andWallace (1994) summarize the various classification

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Table 2 Areas of potential zones for spring formation

(1) Spring recharge areas 722 km2

(rolling hill tops and flat areas)(2) Dissected plateau including steep slopes 623 km2

(3) Water-spread area of the Koyna reservoir 115 km2

(4) Relatively flat areas where groundwater 576 km2

development is through dug wells and bore wells

Total 2,036 km2

Table 3 Classification of springs according to magnitude of dis-charge (Meinzer 1923). l ft.3/s=448.831 gal/min; 1 gallon=4.546 l;1 gal/min=5.3 m3/day

Magnitude Discharge

(ft.3/s, gal/min) (m3/day)

First ≥100 ft.3/s ≥238,000Second 10–100 ft.3/s 23,800–238,000Third 0.1–10 ft.3/s 2,380–23,800Fourth 100 gal/min to 1 ft.3/s 530–2.380Fifth 10–100 gal/min 53–530Sixth 1–10 gal/min 5.3–53Seventh 1 pint to 1 gal/min 1.3–5.3Eighth <1 pint/min <1.3

Table 4 Discharge ranges of springs examined

Discharge range Meinzer’s No. of % of (m3/day) magnitude springs springs

2–12 Seventh/sixth 17 2312–24 Sixth 24 3224–36 Sixth 8 1136–48 Sixth 8 1148–60 Sixth/fifth 4 560–72 Fifth 0 072 Fifth 13 18

Total 74 100

per square kilometre. Although lithology is considered tobe the most important factor affecting recharge, otherfactors including soil type, vegetation cover and slopeare also influential (Sanz Perez 1996). At higher eleva-tion, soils are mostly lateritic followed by black cottonsoils descending the slope. The hills as a whole havesparse vegetation with mostly uniform surface slope con-ditions. Thus, in an area of 722 km2, considered to be therecharge areas for springs, about 725 springs are expect-ed to occur.

Spring Discharges

Discharge Variations vs. TimeThe discharges from an individual or a group of springswere measured wherever possible (74 out of 121). At ornear the origin, the spring water was allowed to fall intoa 20-l bucket and the time taken to fill the bucket in eachcase was noted with the help of a stopwatch. In case of

schemes available in the literature. Although a numberof classification schemes, based on one or many of thecriteria described by these authors, have been developedhistorically by various workers, such as Fuller (1904),Keilhack (1912), Bryan (1919), Meinzer (1923), Clarke(1924), Stiny (1933), Tolman (1937), Netopil (1971),Shuster and White (1971), Bliss (1983), McColloch(1986), Scanlon and Thrailkill (1987) and Sanz Perez(1996), none of these classifications take into accountthe origin, occurrence and source-aquifers altogether.Therefore, a simple classification based on the nature ofemergence and source-aquifers is suggested for the ba-saltic terrain of the Western Ghats. This classificationscheme could be applied to similar basaltic terrains else-where in the world.

The springs of the Western Ghats are mostly gravitysprings, emerging either from the contact between twolitho-units or from fracture surfaces. But because theemergence of groundwater as springs is largely con-trolled by the water-bearing properties of the aquifers inthe study area, these springs can also be classified on thebasis of their source-aquifers as follows.

1. If a spring issues at the contact between the lateriteabove and the lithomarge or poorly lateritized flow orthe massive basalt below, i.e. if the source-aquifer islaterite, the spring may be termed a ‘laterite spring’.

2. If a spring issues at the contact between the talus de-posits above and the poorly lateritized or weatheredhard massive basalt below, the talus deposits form thesource-aquifer, and the spring may be termed a ‘talusspring’.

3. When a spring emerges at the contact between a ve-sicular basalt above and a weathered or hard massivebasalt below, i.e. when the source-aquifer is vesicularbasalt, the spring may be called a ‘vesicular basaltspring’ (or ‘vb spring’).

4. When a spring issues at the contact between a weath-ered massive basalt (source-aquifer) above and mod-erately weathered or hard massive basalt or redbolebelow, the spring may be called a ‘massive basaltspring’ or (‘mb spring’).

5. When a spring issues through a fracture, vertical orhorizontal, it may be called a 'fracture spring’. Frac-tures may not be deep seated, and no specific source-aquifer is involved. The fractures giving rise tosprings are generally found in massive basalts.

From these five subclasses the first four are contactsprings, categorized into four different types dependingon their source-aquifers. Therefore, when one speaks ofcontact springs, it not only gives an idea about the natureof the emergence of springs, but also their source-aqui-fers. Thus, when one speaks of laterite or talus or vesicu-lar basalt springs, one can easily imagine the source-aquifer and the nature of the spring emergence.

The frequency distribution of the occurrence of thevarious types of springs, as proposed, is given in Table 6.

Chemical Quality of Spring Waters

To test water quality from the several types of springs,29 water samples were randomly collected: 21 from ba-salts, five from laterites and three from talus deposits.Eighteen samples were collected separately for the anal-ysis of iron. Springs supplying drinking water to homesand livestock were given priority to unused springs.Temperature of the spring water varied between17–22 °C as against air temperature of 28–32 °C in thewinter. Table 7 gives the mean values and ranges of the

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Table 5 Relationship betweenspring discharges and elevation Elevation No. of springs with discharge ranges Total

range no.(m a.s.l.) (m3/day)

2–12 12–24 24–36 36–48 48–60 60–72 >72

600–700 0 3 1 0 0 0 1 5700–800 3 2 1 2 0 0 1 9800–900 0 3 1 1 0 0 1 6900–1,000 9 11 2 3 2 0 6 33

1,000–1,100 2 2 3 2 2 0 2 131,100–1,200 1 1 0 0 0 0 0 21,200–1,300 1 1 0 0 0 0 0 21,300–1,400 1 1 0 0 0 0 2 4

Total no. 17 24 8 8 4 0 13 74

Springs (%) 23 32 11 11 5 0 18 100

Table 6 Frequency of occurrence of various types of springs

Type of spring No. of Percentage springs of springs

A. Contact springs1. Laterite springs 7 92. Talus springs 17 233.Vesicular basalt spring 15 204. Massive basalt springs 28 37B. Fracture springs 8 11

Total no. of springs 75 100

major chemical constituents. Because samples were un-filtered, the concentration reported may be in excess ofthe true dissolved values, but close to the total concen-trations (Somasundaram et al. 1993). Because all thesesprings are located at higher elevations and most sampleswere collected at or very close to their origins, except ina few cases where they were collected at the point of de-livery of the spring water to the water supply storagetanks, human impact that may change/modify chemistryof these spring waters is minimal. All the spring watershave very low major-ion concentrations. Without excep-tion, HCO3

– is the dominant anion and Ca2+ is the domi-nant cation. In all the samples, the Ca/Mg ratio is greaterthan 1. Na+ concentration is always higher than K+.CO3

2– and SO42– are totally absent. NO3

2– is found in traces in only a few of the samples. The chemical constituents have been plotted on a Hill–Piper diagram(Piper 1944) and a modified Hill–Piper diagram(Romani 1981). These diagrams are shown in Fig. 4. Thesamples on the Hill–Piper diagram plot in three distinctdomains. As per the concept of hydrochemical facies de-veloped by Morgan and Winner (1962) and Back (1966),the spring waters in the cation-triangle could be classi-fied as calcium type while in the anion-triangle theycould be classified as bicarbonate type. Plots in the cen-tral rectangle indicate that the waters are dominated byalkaline earths (Ca2+, Mg2+) and weak acids (HCO3

–,

CO32–). The modified Hill–Piper diagram (Romani 1981)

classifies spring waters under calcium type (84%), calci-um–magnesium type (10%), magnesium type (3%) andsodium type (3%). The central field in this diagram givesthe overall character of waters. The waters falling ingroup I have alkaline earths exceeding the bicarbonates.Such waters show permanent hardness and have no bi-carbonate hazard for irrigation. On the other hand, wa-ters falling in group II have temporary hardness and re-sidual sodium carbonates.

The chemical composition shows distinct variationamong the spring sources. Springs originating from ba-salts show the highest mineralization, followed by thosefrom laterites and the least in the talus deposits. Also,mean pH in the basaltic springs (7.97) is higher thanthose in the laterites (7.76) and the talus deposits (7.70).The concentrations of the chemical constituents in springwaters are dependent on the time they spent in the aqui-fer as well as the aquifer lithology. Talus deposits in thearea have higher porosity, permeability and specificyield, followed by those in the laterites and then the ba-salts (Naik 1994). Therefore, the average travel time forthe same quantity of groundwater for the same distancein basalts is higher compared with that in the lateritesand the talus deposits. In terms of lithology, basalts inthe area are of tholeiitic composition and consist mostlyof plagioclase [(Na, Ca)Al(Si, Al)Si2O8], sub-calcic

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Table 7 Chemistry of spring waters. Figures are mean values; figures in parentheses indicate minimum and maximum values. EC Elec-trical conductivity; TDS total dissolved solids; TH total hardness

Source pH EC TDS TH as Na+ K+ Ca2+ Mg2+ HCO3– Cl– Fe2–

aquifer (No. (mmho/cm CaCO3 (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l) (mg/l)of samples) at 25 °C) (mg/l)

Basalt 7.97 190 97 78 8 0.7 23 5 97 11 –(21) (7.70–8.30) (100–320) (55–160) (40–140) (4–25) (0–4) (12–36) (1–12) (31–177) (7–14) (Tr-0.50)Laterite 7.76 136 70 60 4 0.2 18 4 65 11 –(5) (7.42–7.90) (90–180) (50–95) (40–75) (2–7) (0–0.5) (14–28) (1–6) (31–92) (7–14) (Tr-0.7)Talus 7.70 127 63 55 4 0.33 18 2 63 8 –(3) (7.31–8) (70–200) (35–100) (30–85) (2–7) (0–0.5) (10–30) (1–4) (31–104) (7–11) (Tr-0.45)

Fig. 4 Hill–Piper and modifiedHill–Piper plots of chemicalconstituents of water fromsprings in basalt, laterite andtalus from the Koyna River basin, India

augite [(Ca, Mg, Fe2+,Fe3+, Ti,Al)2] and olivine [(Mg,Fe)2SiO4]. Laterites derived from basalts are highly fer-ruginous and contain irregular pockets and lenses ofbauxite (Thorat and Ravi Kumar 1987). Talus deposits,on the other hand, consist of unconsolidated boulders,pebbles, soils and clays, produced by the down-slopemovement of the weathered and eroded basalts and late-rites. As groundwater flows through strata of differentmineralogical composition, the water composition under-goes adjustments caused by the imposition of new mineralogically controlled thermodynamic constraints(Freeze and Cherry 1979). Because of these constraints,talus deposits in the area have lesser mineralization com-pared with those in the laterites and basalts. Even withinthe same type of source-aquifer, chemical variations areperceptible. For example, in basalts, spring waters atlower elevations in a geologic section usually showhigher mineralization compared with springs at higherelevations. Assuming there is little variation in the basal-tic flow lithology and its chemistry, the residence timefor groundwaters before they emerge as springs at lowerlevels is higher compared with residence time at higherlevels. This also could be a reason, apart from mixing ofwaters from different basaltic flows, why bore-well wa-

ters derived from depth in the area have higher mineral-ization compared with the shallow dug-well waters(Naik et al. 2001).

All the analysed chemical constituents fall within thedrinking water standards set by Indian Standards Institu-tion (ISI) (1983) and World Health Organization (WHO)(1998). However, iron concentrations in about 40% of thesamples (7 out of 18) fall above the ISI (1983) permissi-ble limit of 0.3 mg/l. The high iron concentrations inthese spring waters could be attributed to the ferruginousnature of basalts and laterites. To test the suitability of thespring waters for irrigation, sodium adsorption ratios andpercent sodium of the collected samples were determinedand plotted on USSL (US Salinity Laboratory) (1954)and Wilcox (1955) diagrams. These plots are shown inFig. 5. The USSL diagram classifies spring waters underthe ‘excellent’ category, whereas the Wilcox diagramclassifies them under the ‘excellent to good’ category.

Springs as a Source of Water

Springs are used both for drinking and irrigation purpos-es by the local inhabitants both at higher elevations andin foothill zones. Spring water is even considered holy insome places. For example, Fig. 6 shows a woman col-lecting drinking water from a spring coming from themouth of a statue at the Panchaganga Temple at Old

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Fig. 5 US Salinity Laboratory and Wilcox diagrams, showing so-dium absorption ratio and percent sodium in the spring water ofthe upper Koyna River basin, India

Mahabaleshwar, which is the highest spring location inthe area (1,340 m a.s.l.). In many villages, more than100 acres of land are irrigated from springs. Villagerscombine waters of two or more springs and bring it toone channel to irrigate wheat, sugarcane, rice, vegetablesand other seasonal crops. Generally, spring waters aretapped and supplied to small hamlets by the State Gov-ernment under a ‘gravity water supply scheme’. Oftenwaters from two springs are combined to cater to theneeds of a larger population. A small tank is made at theorigin of a spring and water is allowed to flow by gravitythrough a pipeline to a distribution tank (Fig. 7), whichis located higher than the village to be served. Depend-ing on the quantity of water stored, water is released ei-ther periodically or continually by pipelines to the villag-es for their use.

Among the 30 water supply schemes investigated, 23(~80%) of the schemes were found to be ineffective.Some of the common causes for the poor performance ofthe gravity water supply schemes are (1) tapping of onlyone small spring for a comparatively large population,(2) lack of spring flow through the dry season, (3) pipe-line breaks connecting the spring and the storage tanks,(4) leakage of the storage tanks and silting up of thesmall tanks at the spring, and (5) mismanagement of thealready tapped spring water.

There are cases, in addition to the above, where manylarger springs have been thoughtlessly diverted, thuscausing heavy ecological damage and public outcry. Infact, these springs, while flowing downhill from their or-igins, have formed their own narrow riparian zones oneither side of their flow-paths. These riparian zones usu-ally have heavy vegetation growth. Undoubtedly, theseplant growths and the seeping spring waters support nu-merous organisms, many of which are unnoticed by mostpeople. Also, the seeping spring waters augment thegroundwater recharge of the lower aquifers to supportthe life of the existing springs issuing from these aqui-

fers. These lower elevation springs also have their ownenvirons similar to those at higher elevations. Dependingon their locations, these springs are either utilized by thelocal inhabitants for drinking/irrigation purposes, or theyflow downhill to join the mainstream and continuethrough the hydrological cycle. The interconnected na-ture of all these elements in the environment is often farfrom simple. Thoughtless exploitation of these springs,therefore, may cause much ecological damage and publicdissatisfaction (especially if they are utilized by somehamlets/groups of individuals). Because of all these con-siderations, before diverting any spring, thorough inves-tigations of the affected springs, their environs and theircurrent utilization are highly warranted to safeguard theenvironmental serenity of the region. Because thesesprings are the blood of the region, they must not beover-exploited.

Following are a few suggestions, apart from a keyconcept described above, for effective development ofthe existing springs:

1. Springs should be tapped after a thorough examina-tion of their seasonal discharges, including during thesummer. Water requirements of the villages to be sup-plied with the spring waters must be satisfied.

2. Whenever necessary, two or more springs should betapped together to cater to the needs of a relativelylarger population.

3. After installation of the water-supply schemes, theyshould be monitored.

4. In case water supply exceeds use, the surplus watersmay be stored for future use in horticulture and to irri-gate crop land.

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Fig. 6 A woman collecting drinking water from a spring comingout from the mouth of a statue at the ‘Panchaganga’ (meaning fiveGanges, the holy river of India) temple at Old Mahabaleshwar inthe northernmost part of the upper Koyna River basin. This springis the highest spring location (elevation 1,340 m a.s.l.) in the area

Fig. 7 A storage tank for collection and distribution of spring wa-ter through gravity

5. Rainwater harvesting structures may be constructed atsuitable locations on hilltops for enhancement of thelife of springs and to increase their discharges.

6. The pipelines connecting the spring and the storagetanks may be buried at about 2–3 ft. depth so as toprotect them from detachments because of rockslidesor interference from wild animals.

7. A barbed-wire fence may be constructed around thesprings under use to protect them from human/wild-life interference.

Summary and Conclusions

Origins of springs in a basaltic terrain has been poorlystudied. There is a prevailing misconception that springsissue only from fractures/joints or from basaltic flowcontacts. However, the present study reveals that theirorigins are more dependent on the lithological characterof different basaltic flow units and the terrain physiogra-phy. In the Western Ghats, springs generally issue at thecontacts between (1) laterite and lithomargic clay orpoorly lateritized basaltic flow, (2) vesicular basalt andnon-vesicular massive basalt, (3) highly weathered mas-sive basalt and moderately or poorly weathered massivebasalt or redbole, and (4) talus deposits and hard massivebasalt or laterite or lateritized basaltic flow. Springs alsoemerge from fractures, both horizontal and vertical, andfrom the intersections of fractures with different orienta-tions.

A total of 121 springs were examined during thestudy, which were distributed at an elevation range of650–1,350 m a.s.l. The maximum concentration, 47%,were between 900–1,000 m elevation. Twenty-two per-cent of the springs occur above an elevation of 1,000 m.Springs have an average recharge area of 722 km2 in theKoyna River basin and an occurrence frequency of onespring per square kilometre. Although rainfall and re-charge areas play vital roles in the yields of thesesprings, their yields are largely controlled by lithologi-cal variations and hydraulic characteristics of theirsource aquifers. There is a marked seasonality in thespring flow domain depending on recharge. The meandischarge of the individual springs in winter is about46 m3/day as against a mean discharge of 28 m3/day inthe summer.

Springs of the Western Ghats are essentially contactsprings (89%) and fracture springs (11%). However, be-cause the emergence of groundwater in the form ofsprings is largely controlled by lithology and the result-ing water-bearing properties of the formations, a newclassification scheme is proposed that classifies thesprings on the basis of their source aquifers and nature ofemergence. Thus, contact springs may be further classi-fied into four different categories – ‘laterite springs’, ‘talus springs’, ‘vesicular basalt springs’ (or ‘vbsprings’), and ‘massive basalt springs’ (or ‘mb springs’).This new classification could also be applied to similarbasaltic terrains elsewhere in the world.

The chemical concentrations of the spring waters areheavily dependent on the lithological compositions ofthe source-aquifers and the residence time of groundwa-ters in these aquifers. The waters are dominated by alka-line earths (Ca2+, Mg2+) and weak acids (HCO3

–, CO32–),

and are mostly calcium type (84%) and calcium–magne-sium type (10%). Chemical qualities of the spring watersare well within the ISI (1983) and WHO (1998) drinkingwater standards, except for that of iron (ISI) in about40% of the samples.

One of the purposes of this contribution is to empha-size that the springs of the Western Ghats be tapped ef-fectively for the benefit of humankind. However, it mustbe remembered that they also sustain the life of thou-sands of plants, animals and other organisms and that thediversion/development of these springs would greatly af-fect these life forms. Moreover, as these springs flowdownhill, they also recharge the lower aquifers, thus en-hancing the life of the existing springs at lower levels.Therefore, depending on the situation, a trade-off mustbe made considering local needs and downstream users.Emphasizing only local human needs might lead to se-vere intercommunity conflict and negative environmen-tal consequences.

Acknowledgements The authors thank the people of the WesternGhats for their cooperation in the field studies. Thanks are alsodue to Central Groundwater Board, Ministry of Water Resources,Government of India, for providing the necessary field supportand facilities. All the analyses were carried out in the chemicallaboratory of Central Groundwater Board, Central Region, Nag-pur, India. Suggestions given by Zane Spiegel, Kristine Uhlman,Patty Toccalino, Perry G. Olcott and two anonymous reviewersgreatly improved the quality of the manuscript. Special thanks toZane Spiegel for some of his ideas used in the manuscript.

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