Estimation Of Sedimentation Rates And Useful Life Of Dal-Nagin Lake In Jammu And Kashmir In India Using Radiometric Dating Techniques

摘要

The Dal-Nagin Lake is a Himalayan Lake located in the heart of Srinagar at an average altitude of 1583m. The lake comprises of four major sub-basins, viz., Hazratbal, Bod Dal, Gagribal & Nagin. The first three sub-basin collectively known as Dal Lake while the fourth one has the separate identity due to its specific location. The sedimentation rates have been estimated at different locations in the lake employing Cesium-137 (~(137)Cs) and Lead-210 (~210)Pb) radiometric dating techniques of sediments. The average rate of sedimentation in Dal lake is 0.52 ± 0.04 cm/y since 1964 that stands reduced to 0.22 ± 0.03 cm/y since 1987. Similarly the rate of sedimentation in the Nagin lake is 0.41 ± 0.05 cm/y since 1964 and 0.34 ± 0.03 cm/y since 1987. The estimated useful life of Dal lake, taking an average rate of sedimentation starting from 1964, is about 155 years while for Nagin lake it is about 318 years. However, if we consider post 1986-1987 sedimentation rate the expected useful life of Dal lake comes about 360 years and for Nagin lake about 376 years. It is interesting to note that the average rate of sedimentation has reduced considerably (0.58 cm/yr) in Hazratbal sub-basin after 1986-87 in comparison to the rate of sedimentation since 1963-64 (1.60 cm/y). This may be due to the effect of settlement basin, which has come into existence from the year 1989. It is also found that the organic matters contribute 25-30% in lake sedimentation process. The content of organic matters found in different sediment cores reveals that the incoming water to the lake is contributing less than 10% of organic matters and rest of the organic matters are being contributed by the underwater weeds. It is therefore, important to control the growth of weeds in order to increase the useful life of the lake at least by 25%.