WATER QUALITY INDEX AS A TOOL TO ASSESS WATER QUALITY OF SASTHAMKOTTA FRESHWATER WETLAND, A RAMSAR SITE IN INDIA

Lakes are versatile ecosystems thatperform valuable functions such as recycling nutrients,attenuating floods, recharging groundwater and also serve the water needs of the human populace.Nowadaysthe quality of surface water is getting deteriorating at a rapid pace due to excess waterwithdrawal and various anthropogenic activities. In this study, the water quality status ofSasthamkotta lake, a fresh water wetland in the south western part of India which is also a Ramsarsite is determined in terms of Central Pollution Control Board National Sanitation FoundationWater Quality Index. The study was carried out from the month of October 2018 to the month ofSeptember 2019 and parameters namely dissolved oxygen, faecal coliform, pH and biochemicaloxygen demand were analysed to determine the water quality status of the lake and the same wasmapped using Geographical Information System. It was found that major part of the lake comesunder the category good (Central Pollution Control Board National Sanitation Foundation WaterQuality index [CPCB-NSFWQI] ranging from 78 to 80). Localised moderately good water quality(CPCB-NSFWQI ranging from 76 to 78) was observed at sampling stations namely Bharanikkavuand Anjalimooduand very good water quality(CPCB-NSFWQI ranging from 80 to 82) was foundat the sampling stationnamely Kerala Water Authority main pumping station during the postmonsoonand the pre-monsoon season respectively. It was also found that the major portion of thenorth eastern part of lake comes under moderately good water quality during the monsoon season.Densely populated catchment area of the lake, physical setting of the lake characterised by steepslopes on three sides and excess runoff during rainfall could be attributed to the moderately goodwater quality of the lake. Water quality parameters namely faecal coliform exceeded thepermissible limits as per the Bureau of Indian Standards for drinking purpose at all the samplingstations throughout the study period. The designated best use of Sathamkotta lake belongs to thecategory ClassA (non-polluted source) (as per the various classes given by the Central PollutionControl Board based on the CPCB-NSFWQI values obtained during the study period.