Abstract:
This study investigates the impact of the land use/cover changes on the stream flow and sediment yield of the Deme River. Land use/land cover change has been one of factors responsible for changing the hydrologic response of watersheds leading to impacting stream flows. For water resources planning and implementation, the knowledge of these changes on watershed level were required and important to minimize the undesirable effects of future land use/cover change or modifications. In this study analysis of land cover change between the 2000, 2009 and 2019, and their effects on the catchment hydrology were addressed. Land use maps of 2000, 2009 and 2019 were prepared from satellite images using ERDAS Imagine 2015 software. Land cover change analysis has shown the modification on the land cover classes. The forest class and grass class coverage was decreased by 12.08 % and 16. 34 % respectively during 2000 and 2009, whereas the agricultural land coverage, cultivation land and urban coverage was increased by 17.66 %, 19.07 %, 30.35 % respectively for 2000 and 2009. For 2009 and 2019 forest class, grass land, shrubland was decreased by 12.77%, 38.98%, and 10.3 % respectively whereas urban land was increased by 27.6 %.
The Soil and Water Assessment Tool (SWAT) model was used to examine the impact of land cover change on stream flow and sediment yield. The model was calibrated and validated using measured flow data and sediment data from 1992 to 2004 and validated from 2005 to 2014 for checking accuracy purpose. The correlation coefficient (R2) values for the watershed from calibration of 2000, 2009 and 2019 stream flow were 0.83, 0.82 and 0.8 respectively. The correlation coefficient (R2) values for the watershed from validation of 2000, 2009 and 2019 stream flow were 0.84, 0.83 and 0.81 and Nash‐Sutcliffe Efficiency (NSE) values for the watershed from calibration of 2000, 2009 and 2019 were 0.69, 0.7 and 0.75 respectively. Nash‐Sutcliffe Efficiency (NSE) values for the watershed from Validation of 2000, 2009 and 2019 were 0.72, 0.73 and 0.71 respectively. The mean monthly stream flow in between 2009 land cover and 2019 land cover increased 33%, land cover between 2000 and 2009 showed 27 % increment. The Average annual sediment yield at outlet of Deme River was 6.131 million ton/yr for 2000 LULC, 6.429 million ton/yr and for 6.748 million ton/yr 2019. The sediment yield increased in 10% on past 30 years.
Generally, the
