Modeling Simulation of River Discharge of Loktak Lake Catchment in Northeast India

Abstract

Water resources management requires an integrated approach between sustainability and catchment management to provide an enhanced understanding of usage options and environmental impacts. Discharge contributes significantly to the lake water and hence its accurate assessment would help in designing the management policies. This study simulates river discharge contributing to a lake using different physical and data-based modeling approaches. Models such as support vector machine (SVM); extreme learning machine (ELM); MIKE SHE; and a combination of MIKE SHE and the Soil and Water Assessment Tool (SWAT), the hybrid MIKE SHE-SWAT model, are used to simulate discharge for three subcatchments of Loktak Lake. Discharge simulation at different sections of a river using physically based models is cumbersome because it requires data such as river geometry, hydrologic time series, channel roughness coefficients, and hydraulics of existing control structures. In developing countries such as India, quality and quantity of data become the limitation because of poor monitoring and record keeping. Therefore, a data-based modeling approach can also be used as an alternative tool in hydrologic simulation studies. The selected methods are evaluated using statistical indicators, and results show that both physical and data-based methods satisfactorily simulate the observed hydrograph at the outlet of each subcatchments. This study concludes that using the hybrid MIKE SHE-SWAT model simulates the river discharge with the highest Nash-Sutcliffe model efficiency (NSE), .854 for the Nambul subcatchment, .89 for the Iril subcatchment, and .845 for the Thoubal subcatchment. Subsequently, hydrological models for the other six subcatchments are developed using the hybrid MIKE SHE-SWAT model. Furthermore, water balance components of the Loktak Lake are also analyzed, which suggest that of the total inflows to the lake, discharge from the nine subcatchments accounts for about 91%, and the remainder is contributed by direct rainfall onto the lake area. Among outflows, Ithai barrage (69%) accounts for the largest fraction, whereas abstractions for hydropower generation, evaporation from the lake surface not covered by phumdis, evapotranspiration from the area of phumdis on the lake, irrigation, and domestic consumption account for 22, 2, 5, 1, and 1%, respectively.