Investigating the effects of land use and land cover changes and BMPS scenarios on water balance and sediment yield of the Nakivubo channel micro-catchment in Uganda

Abstract

The increasing demand for freshwater resources due to the growing population requires information on the effects of land use and land cover (LULC) changes on blue and green water resources. This study aimed at investigating the effects of LULC changes and BMPs scenarios on water balance and sediment yield in the Nakivubo micro-catchment of the inner Murchison Bay catchment in Uganda. LULC change analysis between 2005 and 2040 was done by ArcGIS software and the cellular automata Markov model. The Soil and Water Assessment Tool (SWAT) was used to simulate the components of the water balance equation. Results showed that between 2005 and 2040, built-up land and water bodies increased by 1,010 Ha and 60 Ha respectively. Bare land, wetland, and agricultural land declined from 343 Ha to 322 Ha, 85 ha to 7Ha and 1864 Ha to 657 Ha respectively in the same period. Model performance evaluation produced R2 of 0.74, NSE of 0.72 and PBIAS of -0.05 for calibration and R2 of 0.68, NSE of 0.75 and PBIAS of 2.35 for validation. Water flows in 2005 and 2040 were 1096.5 mm and 1278.9 mm respectively, whereas Evapotranspiration plus soil moisture flows were 2482.5 mm and 2522.5 mm in the same period respectively. Surface runoff increased from 207.6 mm to 698.1 mm between 2005 and 2040 and total sediment loading from 5.8 ton ha-1 year-1 to 12.4 ton ha-1 year-1 between 2005 and 2040. Catchment management scenarios reduced sediment load and surface runoff by 79% and 68% respectively. Therefore, the information on the effects of LULC changes and BMPs application on the water balance and sediment yield will be used in global and national water planning and management of water resources for a sustainable catchment.