Abstract:
Mansar lake is situated about 55 km East of Jammu City at an elevation of 666 metres above mean sea level in the Siwalik terrain of Jammu region. Lake surface area is 0.59 km² and lake basin area is 1.67 km². The maximum depth of lake is 38.25 meter. It has been developed as tourist spot in the Jammu region due to its natural beauty. The lake water is also being used for drinking and irrigation purposes. The lake catchment is composed of lower Siwalik rocks, which are highly prone to erosion. It has been felt that Mansar lake is shrinking very fastly due to high rate of siltation.
In recent years radiometric dating techniques (i.e., 137Cs and 210Pb) have been proved as reliable tools for estimation of sedimentation rate. Study of rate of sedimentation and pattern in Mansar lake has been carried out using 137Cs and 210Pb radiometric dating techniques. Five sediment cores at different location from Mansar lake were collected in order to determine the rate of sedimentation. Rate of sedimentation obtained using 137Cs varies between 0.14 to 0.37 cm/y depending upon the location in the lake. Sedimentation rates have also been estimated at three locations using 210Pb dating technique. These vary from 0.24 cm/y to 0.34 cm/y that are comparable with the rates estimated using 137Cs dating technique. The mean rate of sedimentation in lake using 137Cs results is 0.23±0.031 cm/y. Results obtained by 137Cs technique are used to compute the life of Mansar lake. The predicted life based on Post-1964 mean rate of sedimentation of Mansar lake (0.23 ± 0.02 cm/y) is about 9110 ± 790 years.
