Scholarly record

QUANTIFICATION OF SEDIMENT SOURCS IN THE HIGH RELIEF CATCHMENT OF MANGLA RESERVOIR, PAKISTAN

M. Nawaz, R. J. Wasson, W. Ahmad, D. Pearson, D. L. Parry, F. Sattar

Abstract

Sedimentation in water reservoirs is a serious problem observed throughout the world. Its reduction is critical to ensure sustained socio-economic development. Mangla reservoir, the largest earth filled reservoir in Pakistan, was completed in 1967 with a gross storage capacity of 7280x106m3. Over the years (1967-99), this dam has been plagued by a massive inflow of sediments resulting in a reduction of 19 \% of its total storage capacity. This led to not only a decreased water supply to the farming community but also reduced hydro-electricity generation seriously impeding the industrial growth of Pakistan. The 2005 Kashmir earthquake further aggravated the land sliding and sediment transportation problem in the Mangla catchment resulting in the reduction of the reservoir’s life and its capacity. Currently, no scientific attempts have been made to understand the sources of the sediments in the reservoir and craft sediment reduction strategies. In this paper, results of a study focusing on the quantification of sediment sources based on measured sediment loads and top soil tracers 210Pb(ex) and 137Cs are presented. This is the first study of Mangla Reservoir catchment based on geochemical tracers and sediment load data from the gauging stations situated in the catchment area. The data analysis shows that the foothills (the Siwaliks) are yielding 2.2 times more sediment than the hinterland (areas upstream of the Siwaliks). Channel erosion and landslides dominate sediment sources in the hinterland and, unexpectedly, sheet erosion dominates in the Siwaliks.

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