Understanding hydrogeomorphic and climatic controls on soil erosion and sediment dynamics in large Himalayan basins

Swarnkar, S and Tripathi, S and Sinha, R (2021) Understanding hydrogeomorphic and climatic controls on soil erosion and sediment dynamics in large Himalayan basins. In: Science of the Total Environment, 795 .

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Abstract

The Himalayan basins are characterised by severe soil erosion rates and several basins are among the largest sediment dispersal systems in the world. Unsustainable agricultural activities increase the soil erosion rates and influence the overall hydro-geomorphic regime of river basins. Consequently, the water holding capacity of soil reduces, which enhances the flood risk in the lowland regions. In addition, excessive sediment flux severely affects the reservoir capacity in the mountainous regions, thus amplifying the flood hazard in the upland regions. Here, we have analysed two large and hydro-geomorphically diverse Himalayan River basins, namely, the Ganga Basin (GBA) from source to Allahabad in northern India and the Kosi Basin (KB) draining through Nepal and north Bihar plains in eastern India. Based on RULSE and region-specific SDR modelling framework, which includes model calibration, validation and uncertainty assessment, we demonstrate that spatial variation in rainfall, hydrogeomorphic conditions, the presence of hydraulic structures, and large-scale agricultural activities influence the overall pattern of sediment production and transport in these two large river basins. Total soil erosion in GBA and KB are estimated to be ~404 × 106 t/y and ~724 × 106 t/y respectively, a large part of which comes from the mountainous regions in both basins. Sediment yield at the mountain exits of the GBA and KB are computed as 14.1 × 106 t/y and 86.4 × 106 t/y respectively, which work out to be ~5% and ~15% of total soil erosion from the respective contributing areas of the KB and GBA respectively. Similarly, sediment yields at outlets in the alluvial plains are estimated to be 32.2 × 106 t/y and 37.3 × 106 t/y in the GBA and the KB, respectively suggesting that a large part of sediments are accommodated in the alluvial plains of KB. These results have significant implications for sediment management in the Himalayan River basins.

Item Type:	Journal Article
Publication:	Science of the Total Environment
Publisher:	Elsevier B.V.
Additional Information:	The copyright for this article belongs to Elsevier B.V.
Keywords:	Agriculture; Floods; Reservoirs (water); Rivers; Sediment transport; Soils; Uncertainty analysis; Watersheds, Agricultural activities; Ganga basin; Landscape diversity; Mountainous regions; River basins; RUSLE; SDR; Sediment yields; Soil erosion; Soil erosion rate, Erosion, basin analysis; erosion rate; landscape structure; Revised Universal Soil Loss Equation; river basin; sediment transport; sediment yield; soil erosion, Bihar; Ganges Basin; Himalayas; India; Kosi Basin, environmental monitoring; India; river; sediment; soil; soil erosion, Environmental Monitoring; Geologic Sediments; India; Rivers; Soil; Soil Erosion
Department/Centre:	Division of Interdisciplinary Sciences > Interdisciplinary Centre for Water Research
Date Deposited:	21 Feb 2023 04:48
Last Modified:	21 Feb 2023 04:48
URI:	https://eprints.iisc.ac.in/id/eprint/80499

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