Temporal, spatial and size variation in the sediment transport in the Krishna River basin, India

Abstract

The total sediment transport of the Krishna River to the Bay of Bengal is estimated to be 4.11 × 10 6 ton yr −1. The sediment load decreases sharply from 67.72 × 10 6 ton yr −1 from the upstream region ((Morvakonda) to 4.11 × 10 6 ton yr −1 at the river mouth (Vijayawada). The depletion of sediment supply in the river mouth and lack of uniformity in sediment transport within the basin is mainly due to several human activities such as dams, cropping, etc. This has been substantiated by the temporal and spatial variation of the suspended sediments based on fourteen years data (1971–1984). One of the tributaries of the Krishna, the Bhima River is the main sediment contributor to the Krishna with an average annual sediment transport of 25.91 × 10 6 ton and sediment concentration of 2070 mg 1 −1. The bulk of sediment transport (> 95%) takes place in the monsoon period. Erosion rate shows no systematic relationship either spatially or temporarily. The total sediment erosion of the Krishna is estimated to be 16 ton km −2 yr −1. Rates of erosion calculated for various subbasins indicate that smaller basins erode more rapidly than larger basins. The particle size distribution of the suspended sediments were correlated with the mean monthly sediment transportation to evaluate the downstream and temporal variation of grain size with sediment transport. At the river mouth, it is seen that enormous amounts of fine particles (1–10 μm) add to the monthly sediment load of the river.