ESSMENT OF THE IMPACTS OF LULC AND CLIMATE CHANGE ON THE MAGNITUDE OF RUNOFF PEAK AT THE OUTLET OF THE LESHKA (STAGE-I) CATCHMENT

Abstract

The response of the catchment to rainfall is greatly influenced by the changing climate and increasing human activities, which affect the hydrologic aspects of the catchment through different parameters, thereby altering the volume of runoff and peak flows. In this study, the assessment of the impact of Land Use and Land Cover (LULC) change and climate change on the magnitude of runoff peaks was quantified for the near future (2030-2050) within the Leshka-I catchment using GIS techniques and HEC-HMS model by incorporating the biascorrected CMIP6 data under different scenarios of SSP245, SSP370 and SSP585 respectively. In this study, LULC maps of the study area for the years 2001, 2011 and 2020 were prepared from Landsat 7 ETM satellite images using ArcGIS’s maximum likelihood classification approach. Using historical LULC maps, future LULC maps were predicted using the MOLUSCE plugin in QGIS 2.16. To evaluate the HEC-HMS model’s performance, the model was calibrated for the monsoon season (May-August) for the year 2021 and validated for the year monsoon seasons of 2019 and 2020. The model performance was assessed using statistical matrices such as Coefficient of determination (R2), Nash Sutcliffe Efficiency (NSE), Percentage Bias (δb) and Root Mean Square Error (RSR). Based on these statistics, the model was found to be good. Further, for climate change impact assessment, the best-performing biascorrected GCM was selected out of an ensemble of 13 CMIP6-GCMs, which was further used for the simulation of runoff peaks along with projected LULC changes (2020-50). Based on the results, it can be demonstrated that the maximum runoff peak of 916 m3/sec, 1220.9 m3/sec, and 1038.8 m3/sec is expected for the years 2021-30, 2031-40, and 2041-50 respectively as per the SSP245, SSP370, and SSP5 scenarios. However, due to the small-scale changes of LULC within the Leshka (Stage-I) catchment the amount of LULC impacts on the runoff generation is found to be very less till the year 2050. This study may be helpful for reservoir operation and for the safety management of the Leshka (Stage-I) dam to prevent the adverse effects of the sudden rise of runoff peaks due to climate change.