Sedimentation study of Mansar lake in Udhampur – A research report by National Institute of Hydrology

The report presents a sedimentation study of the Mansar lake in Udhampur district situated about 55 kms east of Jammu at an elevation of 666 m above mean sea level in the Siwalik terrain. The lake surface area is 0.59 sqkm whereas the lake basin area is 1.67 sqkm. The maximum depth of lake is 38.25 m. The lake has been developed as a tourist spot of the region owing to its natural beauty. The 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 is being increasingly felt that the Mansar lake is shrinking very fast due to high rate of siltation.

In recent years radiometric dating techniques (i.e., ¹³⁷Cs and ²¹⁰Pb) have emerged as reliable tools for estimation of sedimentation rate. The 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 locations were collected from Mansar lake in order to determine the rate of sedimentation. The rate of sedimentation obtained using ¹³⁷Cs varies between 0.14 to 0.37 cm/yr 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/yr to 0.34 cm/yr that are comparable with the rates estimated using ¹³⁷Cs dating technique. The predicted life based on post 1964 the mean rate of sedimentation in the lake (0.23±0.02 cm/yr) is about 9110±790 years.

The Mansar lake with its smaller catchment area, larger lake surface area and comparatively lesser anthropogenic activities has a rate of sedimentation comparable to Kumaon lakes, which implies that its catchment is more prone to erosion.

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