000			05061nam a22001937a 4500
003			OSt
005			20220107122854.0
008			190820b xxu||||| |||| 00| 0 eng d
040			_cIIITMK
100			_aMaha Madhu (41618008) _916303
245			_aGeo environmental indicators of vellayani lake of Thiruvananthapuram district, Kerala
300			_aMPhil EI (2018-2019)
500			_aVellayani lake with a spread area of about 3.98 km2 is the second largest fresh water lake in the Kerala state. The lake is located in the outskirts of Thiruvananthapuram District and lies between the North latitudes, 8024'90" and 80 26'30" and East longitudes, 760 59'08" and 76 59'47". It is getting polluted consequent to the discharge of toxic contaminant from urban and agricultural areas. Lake of adequate baseline information is one of the major constrains challenging conservation & efficient use of freshwater resources. At present, the the lake Vellayani is disappearing in an unpredictable pace. Several reports have been published on the present condition of Vellayani lake. The area of the lake has been reduced to a little less than half the area of what previously existed (750 hectares in 1926). The scenic fresh water lake, at present is being strangulated by the invasive plant species. A thick layer of grass has made some portions near the banks as marshy grassland. Over the years, the lake has been filled with invasive plants such as Eichhornia crassipes, Limnocharis flava, Salvinia molesta, Salvinia auriculata, Cabomba Caroliniana, Lemna Minor and lotus (Cultivated for temple uses). All these indicates that the lake is under heavy threat mostly due human intervention. The present study was conducted as an attempt to evaluate the present geo-environmental status of the lake. Several physico-chemical parameters were analysed, which included Temperature, pH, EC, TDS, Turbidity, Salinity, TSS, Calcium, Magnesium, Sodium, Potassium, DO, CO2, Cl-, NO3, NO 2, NH3, SO42-, PO4, SiO4, Alkalinity as well as heavy metals like Iron, Copper, Cadmium, Lead and Zinc. The Chl-a concentration was also estimated in the lake water, those concentrations showed that the lake was in oligotrophic. category. The physico-chemical parameters like EC, TDS, TSS, DO, CO2, NO2, NH3, PO4 as well as the heavy metal iron and cadmium. Highly significant correlation was found in the study, where EC strongly correlated with TDS & Salinity, pH strongly correlated with DO, PO4 with NO3, Mgwith HCO3 and TA and HCO3 with TA. SiO4 showed a strong negative correlation with K. As per the Gibb’s diagram, the samples fall in the rock-water interaction dominant area. Irrigation suitability of the samples were analyzed, various indices were considered to find the suitability and they were sodium percentage, sodium adsorption ratio (SAR), Kelly’s Ratio, Residual Sodium Carbonate, Potential salinity, Permeability Index and Mg Hazard. As per the Kelly’s ratio about 64.31 percentage of samples were unsuitable for irrigation. All the samples belonged to the excellent category of sodium absorption ration classification. Salinity and alkalinity hazard class diagram (USSL) showed that all lake water samples fall under high salinity with low sodium (C3– S1) class. The Sodium percentage ratio index showed that almost 64% of the lake water samples fall under excellent category. The Wilcox diagram showed that about (78.57%) fell under permissible to doubtful. RSC values of the samples ranged from1.045to 0.0592. Based on the US Salinity Laboratory (1954), all the samples have values <1.25 meql-1 and are safe for irrigation purposes. Based on the Doneen criteria, all the collected samples came under Class ΙΙ which is categorized as good for irrigation. High values of potential salinity in the area can be ascribed to due to comparatively high values of chloride and sulphate content in the study area. About 99% of the samples were within the recommended limits and are suitable for irrigation purposes. As per WQI, only 14 % of samples came under excellent category. The higher values of nitrites, ammonia, phosphate, TDS and TSS along with the organic carbon content in the sediments (Krishnakumar and Baijulal, 2006), are suspected to be the reason for the growth of aquatic floating plantation in the lake. These parameters indicate that the water is mainly polluted by the agricultural and urban runoff. From the overall analysis, it was found that the lake water of Vellayani is portable for drinking water purposes only after pre-treatment. The overall irrigation suitability of the lake was found to be moderate. This study recommends to take proper action against unscientific agricultural activities and also recommends for the proper treatment of the lake water before using for irrigational as well as drinking water purposes.
502			_bMPhil EI _c2018-2019 _dINT _eDr. R Jaishankar
650			_aGEO ENVIRONMENTAL _916304
650			_aPHYSICO-CHEMICAL PARAMETERS _916305
650			_aLAKE WATER QUALITY _916306
942			_2ddc _cPR
999			_c6610 _d6610