Renuka Lake ecosystem and wetland protection, Lesser Himalaya ...

Renuka Lake ecosystem and wetland protection, Lesser Himalaya,Himachal Pradesh, IndiaDAS Brijraj.KGeology of Department, Panjab University, Chandigarh-160014(India)E.Mail:bkdgeochem@yahoo.inAbstract The oval-shaped Renuka Lake islocated at an elevation of 620m above mslin Himachal Pradesh. The lake follows ariparian course between steep hill slopes onboth the sides with thick forest. The lake isalkaline, Ca 2+ + Mg 2+ are the major cationsand HCO 3 - and SO 42-are the major anions.The high SO 4 2- in the lake water is derivedfrom black carbonaceous shale and gypsumof the lithology. The total hardness of lakewater exceeds the prescribed limits henceunfit for drinking, washing, and agriculture.The Na, K, and Cl are deficient in RenukaLake. The variation in the chemistry of thelake water is primarily due toanthropogenic activity and the ripariancourse of lake. The drop of trashes by thetourists and seepage of inlets of domesticand municipal sewage has resulted in thegrowth of the macrophytes particularly inthe extreme west of Renuka Lake wheretourist lodge, temples and bathing ghats arelocated. The growth of weeds causesdeficiency of D.O leading to eutrophicconditions and consequent fish mortality inthe lake. The lake water in contact with soilin the riparian zone show variation in somemajor and trace elements. The vegetation inriparian zone affect both the quantity andquality of water. The wetland sedimentchemistry shows enrichment in Al 2 O 3 ,Fe 2 O 3 , K 2 O,TiO 2 and trace elements Y, Zr,Ni, Th, U and Nb compared to lakesediments and the latter shows similaritywith Post Archean Australian shale(PAAS)indicating higher clay fraction in wetland.Therefore, the variation in water chemistryof riparian zone is soil controlled. Thehigher Zr/Hf ratio of lake sediments andwetland suggests that these elements arecontrolled by zircon. The higher Zr/Yb andZr/Th ratios in wetland sediments comparedto lake sediments show mineral sorting(fractionation) during process of lighterparticles (clays) being trapped in thewetland soil concentrating heavy mineralsin sediments. This shows wetland control inthe flow of nutrients and metal ions in thelake basin. The removal of plant cover, roadconstruction and widening have acceleratedsilting in lake (3.3mm/yr).In order to reducesilt flow dredging has been carried outsuccessfully in the wetland.Key words Alkaline, Dredging, HimachalPradesh, Renuka Lake, Riparian course,Soil control.1.IntroductionThe lake ecosystem is disturbed byvarious factors such as natural and manmade. The natural factors may includeclimate, acid rain, nuclear fall out, landslide, etc. But impact of man made factors,in most of the fresh water lakes, arepronounce and detrimental. Discharge ofpollutants from point and non-point source,deforestation, extensive cultivation,building construction, road constructionand widening, setting of industries,discharge of untreated effluents, domesticsievage etc. not only pollutes the waterbody but also causes increased silt flow inthe lake basin making it shallow hencecutting short the life span of the lake.The Riparian zones have the capacity tobuffer surface water bodies from non-pointsource run off from agriculture, urban or1

other land uses. It even absorbs sediment,chemical nutrients and other substances innon-point source run off. Riparian zones areinstrumental in water quality improvementfor both surface and water flowing intowater bodies through sub-surface or groundwater flow. The wetland riparian zonesshows a particularly high rate of removal ofnitrate entering a stream and thus has aplace in eutrophication management.Because of there prominent role insupporting a diversity of species, riparianzones wetland are often the subject ofnational protection in a Biodiversity ActionPlan.Renuka Lake having a riparian courseand a wetland shows water quality control,soil conservation, their biodiversity andinfluence on aquatic ecosystem. Toestablish these characters a comprehensivestudy of water quality, lake and wetlandsediment geochemistry, isotope chemistryto determine rate of sedimentation, andsurvey of flora and fauna distribution havebeen carried out. The lake is unique inlesser Himalaya and is under RamsarConvention Environment Act.2. MethodologyThe water samples were collected in prewashed1L polythelene bottles filling it tothe capacity. Within 5-6 hours of collectionpH, E.C, D.O, TDS etc. were measuredusing portable field kit. The samples werefiltered using 0.45 µm Millipore filtermembranes. A part of this was used formeasurement of carbonate and bi-carbonateby acid titration, choride by AgNO 3titration, sulphate by Ba(ClO 4 ) 2 titrationafter passing the samples through cationexchange resin, phosphate by an ascorbicacid spectrophotometry, silicate bymolybdenum blue spectrometry. Na, K byflame photometer and Ca and Mg by AAS2100(Perkin Elmer Atomic AbsorptionSpectrophotometer).The sediment samples carefully selectedwere collected from lake and wetland, driedand processed. The samples were ground to-200 mesh size in agate mortar and wereused for making pellets. These pellets weresubjected to X-ray fluorescencespectrophotometer (energy dispersive,Phillips EXAM-6 system) and major andtrace elements were estimated. Theaccuracy was checked by running USGSsediment standards SDO1, SCO1, GSD9and SO1. The major element accuracy is~2.5%. The REE’s were measured on ICP-MS using G2 and SDO1 standards in theUniversity of Kiel, Germany. As the REE.sare present in minor quantities in the matrixelements, therefore, elements have to beseparated as a group so that the spectralinterference from the matrix elements canbe avoided. The precision of data is betterthan 5% except for Ce and Nd, which haveprecision of about 10% and for REE(

The average rain fall in the region isbetween 150-199.9 cm per annum (Joshi,1984) 1 . The Renuka Lake is 10.50m inlength and 204m in breadth with amaximum depth of ~13m and catchmentarea is ~254.3ha.The catchment rocks of Renuka are darkcarbonaceous shales and slates, closelyinterbedded with thin slaty quartzitebelonging to Infra Krol Group. The slatyquartzites, or clay slates are frequentlycalcareous and consists of quartz, carbonate,sericite and pyrite and in some caseschlorite. The green-gray calcareous shaleand argillaceous limestone with variablegradation are of Krol A Group. The purpleredshales with intercalation of green-shalesand thin dolomitic cherty limestone belongto Krol B Group. The well bedded grayishwhitelimestone with shale represents KrolC. The rock formation belongs to neo-Proterozoic – Proterozoic age. (Auden,1934) 2 . The soil composition of the regionalso show a heterogeneous mixture ofcarbonate rocks, sandstones, shales,siltstone in various proportion (Srikantiaand Bhargava,1998) 3 . The soil cover is thindue to weathering-limited conditions(Stallard and Edmond, 1987) 4 as physicalerosion has been stronger due to upliftingHimalaya.4. Water quality of Renuka LakeThe lake water is alkaline, pH rangesbetween 8.21 to 8.55 in the month ofMarch-April. The carbonate alkalinity is2.45 meq/l average. Ca 2+ and Mg 2+ are themajor cations and contribute 38.57 to48.93% and 44.71 to 54.16% of the totalcation budget, respectively. The HCO - 3 andSO 2_4 are the major anions contributing36.97b to 51.90 and 43.25 to 51.91% to theanion budget, respectively. The high Ca 2+ +Mg 2+ -and HCO 3 in water indicatedissolution of limestone in the lake basinwhich is supported by (Ca 2+ +Mg 2+ -):HCO 3equivalent ratio of ±2.55.The high SO 2_ 4 inthe lake is derived from black carbonaceousshale and gypsum in the lithology. Duringweathering process rocks exposed to theatmosphere come in contact with dissolvedO 2 (rain water) that reacts with pyriteresulting in oxidative decompositionproducing H 2 SO 4 by the followingreactions:4FeS 2 +15O 2 + 8H 2 O→2Fe 2 O 3 + 8H 2 SO 4H 2 SO 4 →2H + SO 2_ 4 (Berner and Berner,1987) 5 ……………………(1)As water draining rocks where sulphideoxidation is taking place, the presence ofcarbonate minerals neutralizes acid andhence the pH of lake water remains alkaline(Das and Parkash, 2001) 6 . The contributionof Na and K is between 4 and 7% of themajor ion budget of the lake. The low+(Na+K)/T Z ratio (0.058) indicates thatthere is no significant contribution ofcations to the lake water from thedegradation of alumino-silicates. Thedepletion in K compared to Na may be dueto its resistance to weathering and that K + isutilized in the formation of clay mineralillite. As the hardness of water exceeds theprescribed safe limit hence unfit fordrinking, domestic and agriculture use. Thevariation in chemistry of water is related toanthropogenic activity and riparian wetlandzone. It is observed that PO 2_ 4 and in somecases SO 2_4 in water samples in contactwith wetland are depleted (1.5 to 3.5µg/land 120 to 135 mg/l, respectively) where asthere concentration is enhanced in samplestaken from wetland (12.0 to 13.5 µg/l and150 to 160 mg/l, respectively).The variationshows that these nutrients are adsorbed invegetation/soil thus protecting the lakewater from further pollution. The traceelement content of Renuka water showhigher concentration of Fe and Pb in3

samples close to the hotel, temples, bathingghat where human activity viz-a-vizpollution is maximum (Fig.2; Table 1). Incomparison to lake water, samples alongthe contact of wetland and riparian zoneshow depletion in metal ion concentrationexcept relative enhancement of Sr. Thelatter may indicate higher carbonate inwater as Sr has chemical affinity withcarbonate minerals and enter into latticestructure of calcite. Other metal ions Cu, Cdetc. do not show significant variation.4.1 Water quality and phytoplanktonThe phytoplankton being the primaryproducers constitute the basic food sourceof the lake which supports fish and otheraquatic animals. As the lake is rich innutrients it supports a high biologicaldiversity(Melkania,1988) 7 .The macrophyticvegetation covers an area of 39,969 sq. min Renuka lake. According to Singh andMahajan (1987) 8 the chief macrophyticgenera are Phragmites, Acorus, Typha,Carex, Pontederia and Veronica whichtotals to 42 in number. It is observed thatthe total number of phytoplankton werehigher in April and October which areindicators of pollution. In addition bluegreen algae developed in large number inOctober when the temperature of lake waterwas between 19 0 to 24 0 C but their numberdecrease in August when the temperature ofwater increased. It is observed that thenumber of Myxophycean members weredirectly correlated to the concentrations ofnitrate-nitrogen (NO 3 -N) and inorganicphosphate phosphorus. Phosphorous andnitrogen are transported into the lakethrough soil particles from agriculture lands,animals dung, sewage discharge, andcultural activities. The higherconcentrations of dissolved inorganicphosphate phosphorus was recorded inApril and October and low in June andAugust which corresponds to the high andlow number of phytoplankton population inthe lake (Singh and Mahajan, 1987) 8 . Weedinfestation also leads to oxygen depletionand consequent fish mortality particularlyin morning hours.5. Sediment geochemistry of Renuka Lakeand wetlandAmong the major elements Al 2 O 3 , Fe 2 O 3 ,K 2 O and TiO 2 are enriched in wetlandcompared to lake sediments and as theseshow positive correlation with Al 2 O 3 inboth the cases, it indicates a commonsource viz., phyllosilicates. The traceelements Y, Zr, Ni, Th, U and Nb areenriched in wetland compared to lake andshow similarity with Post ArcheanAustralian Shale (PAAS) indicating clayrich sediment in the wetland. A high Zr/Hfratio of 30 for lake sediments and 33 forwetland suggests that these elements arecontrolled by zircon since these values aresimilar to those reported by Murali et al(1983) 9 from the analysis of zircon crystals.The Zr/Yb, Zr/Th ratio are higher inwetland sediments as compared to lakesediments though these ratios are expectedto be higher in sandstones than in shales butas the wetland is enriched in alumina itindicates more of shale component. Thisshows mineral sorting (fractionation)during process of lighter particles (clays)being trapped in the wetland soilconcentrating heavy minerals (zircon) insediments. This is also reflected fromnegative correlation of Gd N /Yb N with Al 2 O 3and a strong positive correlation with SiO 2in wetland sediments. This shows that thewetland restricts the flow of nutrients, metalions to the lake basin during catchment runoff, due to precipitation in the monsoonseason and also checks the flood water flowin the lake (Das, Birgit and Parkash,4

2008) 10 .In addition grazing and roadconstruction and similar other humanactivities accelerate the silt flow in thewater body which has been measured 3.3mm/Yr by Pb 210 isotope method (Das andKaur, 2001) 6 . During rainy season silt flowwill increase with such anthropogenicactivities. This shows that theanthropogenic intervention is the maincause of environmental degradation ofRenuka Lake. The study shows, over theyears, the human activities have increasedmany fold throughout the Himalaya as aconsequence most of the water bodies inlesser Himalaya are eutrophic and/or inadvanced stage of trophic evolution. InHigher Himalaya population is sparse hencesituation is some what different exceptglacial silt flow in the water body is likely.6. Renuka wetland protectionThe problem of degradation of lakes andwetlands can be controlled effectively byadopting technical and socio-economicconditions of local people. An integrated Vprogram involving measures to combatunplanned growth of settlements and landuse may be a lasting solution.The Himachal Pradesh Government hastaken steps for dredging the wetland toprotect from further silt flow to the basin,control water pollution, save aquatic lifeand people, check flood water. Besides thisafforestation and planting of soil bindingtrees are being carried out to hold the soilfrom rapid erosion. Some importantmeasures to be followed for protection ofwetland are (i) throwing of householdgarbage in the water body be prevented bylaw, (ii) construction of building roads etc.should be restricted to the minimumnecessity, (iii) periodical cleaning of opendrains and selective harvesting ofmacrophytes, particularly the emergent andsub-merged , at the time of peak growth can·Tab. ;1 Trace elements content of water samples of RenukaLake (µg/l)Sample No Pb Cu Cr Zn Co Fe Cd SrRn 1 100 10 40 10 - 80 10 770Rn 2 100 10 30 - - 40 20 650Rn 3 100 10 20 10 10 60 10 620Rn 5 100 10 30 10 10 30 10 690Rn 6 100 - 10 20 30 30 10 610Rn 11 100 - 10 20 20 70 630Rn 16 200 10 20 - 10 120 10 600Rn 17 100 - 20 10 20 80 10 590Rn 19 100 10 30 30 20 70 - 610Rn 20 300 10 30 20 30 50 - 560Rn 21 200 10 20 10 30 60 - 630substantially reduce nutrients from the lakesediments,(iv) harvesting of weeds shouldbe increased to control excessive weedgrowth ,(v) public awareness should bepropagated for their involvement to protecttheir own property,(vi) water qualityparameters should be checked from time totime for its pollution.Reference[1] K.L.Joshi, Geography of HimachalPradesh. National Book Trust , Delhi,1984.[2] J.B.Auden, The Geology of Krol Belt.Rec. Geol. Surv. India, vol 67(4), 357-454,1934.[3] S.V.Srikantia, O.N.Bhargava, Geologyof Himachal Pradesh. Geol.Soc.India.Mem. Bangalore, 1989.[4] R.F.Stallard, J.M.Edmond, Geochmistryof the Amazon, the influence of Geologyand weathering environment on thedissolved load. Jour. Geophys.Res.88,9671-9688, 1983.[5] E. K. Berner, R.A. Berner, The globalWater cycle. Prentice-HallInc., Englewood Cliffs.N.J, pp.3971987.5

[6] B. K. Das, P. Kaur, Major ionchemistry of Renuka Lake andweathering processes, SirmaurDistrict, Himachal Pradesh, India.Environmental Geology (USA), 40,908-917, 2001.[7] N.P.Melkania, The Himalayan Lakesand Wetland Overview. Ind. Jour.EnvironmentalProtection,vol.8,11,November 1988.[8] R. Singh, I. Mahajan, Phytoplanktonand water chemistry of Rewalsar andRenuka Lakes, Himachal Pradesh,Indian Jour.Ecol., 14(2),273-277, 1987.[9] A.V.Murali, R.Parthasarthy,R.Mahadevan, T.M.Sankar, M.Das,Trace element characteristics, REEpatterns partition coefficient of zirconsfrom different geologicalenvironments-A case study of Indianzircons. Geochim.Cosmochim. Acta.47, 2047-2052.[10] B.K.Das, G.Birgit, P.Kaur,Geochemistry of Renuka Lake andwetland sediments, Lesser Himalaya(India): Implications for source-areaweathering, provenance, and tectonicsetting. Environ. Geol.(USA),54,147-163, 2008.6

Table 2. Rare Earth Elements( REE) Data ((REE)datain(ppm)ofselectedsedimentssamples sedimentof Renuka Lake andWetlandSample No. LAKE WETLANDGR I GR II GR III GR VII NGR I NGR IV NGR V NGR VILa 35.4 25.1 28.4 24.9 44.6 46.3 41.6 43.1Ce 72.8 51.7 58.8 50.4 88.8 94.9 85.1 87.3Pr 8.08 5.8 6.5 5.75 10.3 10.3 9.51 9.91Nd 30.5 21.9 24.4 22.1 39.1 38.9 35.9 37.8Sm 6.24 4.49 5.07 4.48 7.87 8.06 7.62 7.84Eu 1.18 0.85 0.97 0.92 1.61 1.55 1.43 1.57Gd 5.48 3.98 4.54 4.36 7.44 7.23 6.95 7.2Dy 4.81 3.58 3.7 3.81 6.79 6.51 6.36 6.69Ho 0.98 0.75 0.74 0.77 1.4 1.35 1.3 1.35Er 2.72 2.02 2.13 2.1 3.75 3.8 3.49 3.69Tm 0.41 0.29 0.29 0.29 0.53 0.56 0.51 0.52Yb 2.67 1.99 2.14 2.03 3.6 3.78 3.51 3.62Lu 0.41 0.31 0.33 0.32 0.56 0.59 0.54 0.58åREE 171.67 122.75 138.01 122.23 216.35 223.83 203.81 211.17LaN/YbN 8.96 8.52 8.97 18.29 8.37 8.28 8.01 8.05Ce/Ce* 1.03 1.03 1.04 1.01 0.99 1.04 1.03 1.01Eu/Eu* 0.62 0.62 0.62 0.64 0.7 0.62 0.6 0.64CeN/ YbN 7.07 6.73 7.12 6.43 6.39 6.51 6.28 6.25CeN/ SmN 2.82 2.78 2.8 2.72 2.72 2.84 2.7 2.69GdN/YbN 1.66 1.62 1.72 1.74 1.42 1.55 1.6 1.61åLREE 153.02 108.99 123.17 107.63 190.67 198.46 179.73 185.95åHREE 17.47 12.91 13.88 13.68 24.07 23.82 22.65 23.65åLREE/åHREE 8.76 8.44 8.88 7.87 7.92 8.33 7.93 7.867