19-Evaluation of recent trends of sedimentation in Indian lakes using 210Pb and 137CS dating techniques

Abstract

In the present study, 21°Pb and 137Cs dating techniques have been employed to determine the recent sedimentation rates in Nainital, Bhimtal, Sat-tal, Naukuchiyatal lakes of Uttaranchal, Mansar and Dal-Nagin lakes of Jammu and Kashmir, Sagar and Bhopal lake of Madhya Pradesh and Barapani reservoir (artificial lake) of Meghalaya. These lakes mainly represent western Himalayas, Central India and north-east Himalaya.

The weighted mean of sedimentation rates i.e., 1.44 ± 0.18 cm/y in Bhimtal lake, 0.74 ± 0.04 cm/y in Naukuchiyatal lake, 0.84 ± 0.05 cm/y in Sat-tal lake, 0.80 + 0.05 in Nainital lake, and 0.23 ± 0.03 cm/yr in Mansar lake have been observed. The average rate of sedimentation in Dal lake was 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 was 0.41 ± 0.05 cm/y since 1964 marginally reduced to 0.34 ± 0.03 cm/y since 1987. The rate of sedimentation showed two types of sedimentation pattern in the Barapani reservoir located in north-east Himalaya: One part of the reservoir receiving the sediment at higher rate, weighted mean 1.76 ± 0.16 cm/y while the other part comparatively at lower rate of 0.72 ± 0.16 cm/y (weighted mean). In Sagar lake, the sedimentation rate was found between 0.14± 0.02 to 1.68± 0.18 cm/y (weighted mean 0.58 ± 0.02 cm/y) in different parts of lake. The average rate of sedimentation in upper Bhopal lake stands 0.97± 0.16 cm/yr.