NUTRIENT DYNAMICS AND EUTROPHICATION IN LAKES WITH SPECIAL REFERENCE TO RENUKA LAKE, HP

Abstract

Using surfaceanddeepwatersamplescollectedwiththehelpofawatersampler, the proposedworkaimstoevaluatethetrophicstatus,itslimitingfactors,and waterqualityfordrinkingandirrigationpurposes,aswellasdeterminethehydro- chemistryofthelakeinRenukaLakeduringpre-monsoonandjustaftermonsoon. The lake’swaterisslightlyalkaline,withapHrangeof9.09–8.11.Thelake’s turbidityrangedfrom8.62to12.699NTU,indicatingalowlevelofclarity.The Carlson’s index,whichisbasedonSecchidisctransparency(SD),chlorophyll-a (Chl-a), andtotalphosphorus(TP),showsthatRenukaLakehastransitioned from hypereutrophictoeutrophicstate.Accordingtothecorrelationcoefficient, the majorityoftheparametersinthelakecomefromvarioussources.Forlarge- sized algae,nitrogen(TP)limitation,aswellasphosphorus,isacriticallimiting factor forincreasingproductionandtrophicstatusindex.Duringallseasons,Ca2+ and Mg2+ are themajorcations,whereasSO2− is thedominantanion.Renuka Lake’sWQIis431.25inthepre-monsoonseasonanddropsto107.63afterthe monsoon,indicatingthatthewaterisunfitfordrinking.Theincreasingconcen- tration ofF− in thelake,whichiscreatedbyfluorapatite,cryolite,mica,andother minerals, aswellasanthropogenicactivity,isresponsibleforthehigherWQIvalue. Its concentrationexceedsthestandardpermittedlimit,posingaseriousthreatto humansandaquaticlife.Basedonthesodiumadsorptionratio(1.66-1.40meq/l) and Kelly’sindex(0.133-0.199meq/l),thewaterqualityisassessedtobeadequate for irrigation.SeasonalvariationsinCa2+, Mg2+, Na+, K+, chloride,fluride,sul- phate, andotherelementshavebeenobservedinthelake,whichcouldbecaused bychangesintemperature,monsoon,rain,andhumanactivity.Tolimittheris- ing concentrationofseveralphysiochemicalparametersandmaintaintheRenuka Lake,strictmitigationmeasuresarerequired.