Sediment Yield in an Urbanized River Basin: A Case Study of Nambul River, Manipur, India

Sediment controls the physical habitat of river ecosystems. Changes in the amount and distribution of different sediment types cause changes in river-channel form and river habitat. Understanding sediment transport and the conditions under which sediment is deposited or eroded from the various environments in a river basin is therefore critical to understanding and managing sediment and sediment-related habitat in rivers. Sediment transport in rivers is controlled by both the flow and the upstream sediment supply. The objective of this study is to quantify the sediment loading through an urbanized degrading river basin by applying the SWAT model (Soil and Water Assessment Tools) on the Nambul river basin located mostly in Imphal urban and peri-urban region (with urbanization increasing by 8.5% in the basin from 2012 to 2020), draining an area of 217.38 sq km. SWAT model integrated with Geographic Information System were used to simulate the discharge and sediment loading. Model calibration and validation were performed for daily time periods using Sequential Uncertainty Fitting 2 (SUFI-2, ver.2) within SWAT-CUP. Model calibration and validation outputs for daily simulation showed a good model performance for the range of streamflow discharges adopted. Thus the evolution of the average total annual sediment in the Nambul river basin which discharges in Loktak Lake, largest freshwater lake in North East India, is estimated at 11.92 t/ha. The study indicates that SWAT model can be used to simulate the runoff and sediment that are mainly caused by rainfall.