Abstract
The Soil and Water Assessment Tool (SWAT) is a versatile model presently used worldwide to evaluate water quality and hydrological concerns under varying land use and environmental conditions. In this study, SWAT was used to simulate streamflow and to estimate sediment yield and nutrients loss from the Murchison Bay catchment as a result of land use changes. The SWAT model was calibrated and validated for streamflow for extended periods. The Sequential Uncertainty Fitting (SUFI-2) global sensitivity method within SWAT Calibration and Uncertainty Procedures (SWAT-CUP) was used to identify the most sensitive streamflow parameters. The model satisfactorily simulated stream discharge from the catchment. The model performance was determined with different statistical methods. The results showed a satisfactory model streamflow simulation performance. The results of runoff and average upland sediment yield estimated from the catchment showed that, both have increased over the period of study. The increasing rate of runoff can lead to severe and frequent flooding, lower water quality and reduce crop yield in the catchment. Therefore, comprehensive water management steps should be taken to reduce surface runoff in the catchment. This is the first time the SWAT model has been used in the Murchison Bay catchment. The results showed that, if all uncertainties are minimised, a well calibrated SWAT model can generate reasonable hydrologic simulation results in relation to land use, which is useful to water and environmental resources managers and policy and decision makers.
Highlights
Land use change can lead to undesirable effects on ecosystems [1]
Comprehensive water management steps should be taken to reduce surface runoff in the catchment. This is the first time the Soil and Water Assessment Tool (SWAT) model has been used in the Murchison Bay catchment
The results showed that, if all uncertainties are minimised, a well calibrated SWAT model can generate reasonable hydrologic simulation results in relation to land use, which is useful to water and environmental resources managers and policy and decision makers
Summary
Land use change can lead to undesirable effects on ecosystems [1]. Land use and land cover changes are significant causes of water, soil and air pollution [2], which negatively impacts the health of rivers within catchments. Vegetation removal to prepare land for agriculture leaves soil susceptible to massive increase in soil erosion by wind and water This reduces the fertility of the soil rendering it unsuitable for agricultural purposes, as well as transport large volumes of nitrogen, phosphorus, and sediments to streams which can lead to various negative impacts such as increased sedimentation, turbidity, eutrophication and coastal hypoxia of wetlands and rivers. The use of agrochemicals such as herbicides, pesticides, and inorganic fertilizers in modern-day agriculture has hugely contributed to increased levels of pollution in surface water bodies as well as contamination of groundwater through runoff and by way of leaching. This pollution in most cases is toxic to aquatic life [2] and humans. These impacts affect the immediate area but their effects can extend to distant regions [3]
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