Abstract
This paper discusses the hydrological impacts of land use changes on the Olifants Basin in South Africa using the Soil and Water Assessment Tool (SWAT). A three-phase land use scenario (2000, 2007 and 2013) employing the “fix-changing” method was used to simulate the hydrology of the Olifants Basin. Changes in land uses were related to different hydrological responses through a multi-regression analysis to quantify the effects of land use changes. Results reveal that from 2000 to 2013, a 31.6% decrease in rangeland with concomitant increases in agriculture lands (20.1%), urban areas (10.5%) and forest (0.7%) led to a 46.97% increase in surface runoff generation. Further, urbanization was revealed as the strongest contributor to increases in surface runoff generation, water yield and evapotranspiration (ET). ET was found to be a key water availability determinant as it has a high negative impact on surface runoff and water yield. Urbanization and agriculture were the most essential environmental factors influencing water resources of the basin with ET playing a dominant role. The output of the paper provides a simplistic approach of evaluating the impacts of land use changes on water resources. The tools and methods used are relevant for policy directions on water resources planning and adaptation of strategies.
Highlights
Land use and land cover (LULC) is an essential component of the terrestrial ecosystem, influencing various fundamental characteristics and processes such as the hydrological cycle, geomorphological processes, land productivity and animal species [1,2]
Studies have shown that changes in catchment hydrology occur mainly due to alterations in interception, infiltration, evapotranspiration and groundwater recharge which are linked to LULC changes [3,5]
Assessing the impacts of LULC changes on hydrology remains an important step in watershed management strategies inclusive of water resources planning and conservation measures
Summary
Land use and land cover (LULC) is an essential component of the terrestrial ecosystem, influencing various fundamental characteristics and processes such as the hydrological cycle, geomorphological processes, land productivity and animal species [1,2]. Studies have shown that changes in catchment hydrology occur mainly due to alterations in interception, infiltration, evapotranspiration and groundwater recharge which are linked to LULC changes [3,5]. Assessing the impacts of LULC changes on hydrology remains an important step in watershed management strategies inclusive of water resources planning and conservation measures. More so, evaluating the impacts of LULC on the hydrology of the Olifants Basin is important considering its water stressed nature [6]. Quantifying the impacts of LULC on the hydrologic responses of large watersheds presents a major challenge due to the complex LULC–climate–hydrology nexus [7]. Notwithstanding, watershed assessment of hydrological responses to LULC changes has reportedly been achieved through the use of two methods; the paired catchment studies and hydrological modelling [8,9]
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