Impact of land use and land cover changes on streamflow dynamics using SWAT model in uMhlathuze River Catchment, South Africa

Abstract

Land use and land cover (LULC) change alters catchment scale streamflow and recharge dynamics which are modified by precipitation partition into surface runoff and baseflow processes. Water consumption has increased through industrialization, urbanization, agriculture, and changes in LULC are a major concern for sustainable water resource management of the catchment. This study aimed to investigate the impact of spatiotemporal LULC changes on streamflow and recharge dynamics using multitemporal Landsat imagery integrated with Soil and Water Assessment Tool (SWAT) within the uMhlathuze catchment. Supervised classification methods using maximum likelihood techniques were employed to categorize each LULC class in the Earth Resources Data Analysis System (ERDAS-2015) Imagine software for the years 2001, 2013, and 2023. LULC changes showed an increasing trend in built-up areas, forests, and barren land, by 30 km 2 , 119 km 2 and 424 km 2, respectively from 2001 to 2023, while a decreased trend was observed in bushland, agricultural land, and water bodies by 427 km 2 , 117 km 2 , and 29 km 2 . The SWAT model pereformed well, with a good correlation between simulated and observed streamflow. During the calibration period, the model achieved R 2 and NSE values of 0.65 and 0.61, respectively, while validation yielded a values of 0.71 and 0.62, respectively. The findings of the mean annual streamflow in the uMhlatuze catchment declined by 55% between 2001 and 2023. Surface runoff and water yield increased by 13% and 7.6%, respectively, these may attribute to a 46% growth in built-up areas in the study area, while groundwater and evapotranspiration decreased by 19% and 2.1%, respectively. The findings of this study suggest that streamflow dynamics and recharge are contlled by climate variability and LULC. The study recommends that policymakers integrate climate and LULC resilience strategies into urban expansion planning to minimize negative impacts on water resources and support sustainable water resource management.