HYDROCHEMICAL STATUS OF SAMBHAR SALT LAKE: A RAMSAR SITE

摘要

Sambhar lake, a Ramsar site; wetland of international importance, has a surface area of 190 Sq km and lies in 27° 58 N, 75° 55 E. It is a shallow Athalassic and Polymictic lake with depth varying between 9.3 cm to 3m. It can be categorized as a playa as it inundates during rainy season and dries up during summers. The lake exhibits considerable temporal changes in volume and surface area. The hydro-chemical study was carried out for a period of one year; Feb 2012 to Jan 2013 and covered all seasons and one complete hydrological cycle. The total rainfall received during the study period was 603 mm. Average Ambient and Water temperature fluctuated between 18℃ to 42.7℃ and 10.5 to 34℃ and has prominent influence on salinity and water density of the lake. Results show that the lake is halo-alkaline with pH and Salinity ranging between 8.13 to 8.93 and 0.34% to 158% respectively. Salinity in the lake results from evaporative concentration of ions leached from its drainage basin. Alkalinity of the lake water was high with Carbonate and Bicarbonate values falling between 249 to 910 and 849 to 2191 mg/L respectively. Density of lake water varied between 1.5 to 8 Be (Baume). Density is the prime factor controlling salt crystallization. Hardness was recorded between 79 to 660 mg/L. Dissolved Oxygen content fell between 0-8.6 mg/L and were inversely correlated to salinity. Free CO_2 was always absent owing to carbonate dominance. Nitrate and Phosphate appeared in all the samples during the course of study and showed values between 1.3 to 9.6 ug/L and 3.9 to 15.1 ug/L respectively. NaCl Content of lake brine was 98.31%, 98.56% and 98.80% in the months of Oct, Nov and Dec-12 respectively. Dominating cation is Na~+ and dominating anion is Cl: The total annual yield of Salt was 2.2 lac tons.