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.

We present here an evaluation of the water quality of an inland watercourse, the Densu River, using multivariate statistical approaches; Principal Component and Cluster Analyses. Sixteen (16) physicochemical parameters were analysed from river water samples for ten (10) different stations. The sampling campaigns were done for four months, October 2018- January, 2019. Results from the Principal Component Analysis (PCA) revealed that five components with eigenvalues >1 were extracted from the water quality data, depicting 78% of total variation in the data. The first Principal Component (PC) explained 37% variance in the data and correlated highly with ions conductivity (0.97), temperature (0.70), total hardness (0.95), sodium (0.93), sulphate (0.80) and chloride (0.93). The second PC explained 12% variance and was loading high with Turbidity (0.84) and PO₄ ^3- (0.80). The third components explained 11% of the total variance and correlated highly with five-day Biological Oxygen Demand (BOD₅) (0.90) and Chemical Oxygen Demand (COD) (0.72). Cluster analysis (CA) classified similar sampling stations into 3 clusters based on their water quality characteristics. Cluster 1 consisted of S1 (Aplaku), and described as fairly good quality but highly influenced by natural activities such as the sea water intrusion. Cluster 2 comprised of S2, S10, S9, S7 (Weija, Potroase, Koforidua, Mangoase) and described as fairly good water quality, but highly influenced by both natural and anthropogenic activities. Cluster 3 consisted of S3, S4, S5, S6 and S8 (Ashalaja, Afuaman, Pakro, Nsawam and Akwadum) and described as poor water quality was mainly influenced by human activities. The study revealed that pollution sources in the Densu River were mainly from anthropogenic and natural activities; including agricultural, urban pollution, domestic waste discharge, geology and the influx of sea water. It is recommended that, effluents must be treated before discharged into the river and buffer zone policies should be enforced.

Intensified human activities over the past decades have culminated in the prevalence of dire environmental consequences of sediment yield resulting mainly from land use changes. Understanding the role that land use changes play in the dynamics of sediment yield would greatly enhance decision-making processes related to land use and water resources management. In this study, we investigated the impacts of land use and cover changes on sediment yield dynamics through an integrated approach of hydrologic modelling and principal component analysis (PCA). A three-phase land use scenario (2000, 2007 and 2013) employing the “fix-changing” method was used to simulate the sediment yield of the Olifants Basin. Contributions in the changes in individual land uses to sediment yield were assessed using the component and pattern matrixes of PCA. Our results indicate that sediment yield dynamics in the study area is significantly attributed to the changes in agriculture, urban and forested lands. Changes in agriculture and urban lands were directly proportional to sediment yield dynamics of the Olifants Basin. On the contrary, forested areas had a negative relationship with sediment yield indicating less sediment yield from these areas. The output of this research work provides a simplistic approach of evaluating the impacts of land use changes on sediment yield. The tools and methods used are relevant for policy directions on land and water resources planning and management.

The Black Volta River basin faces several challenges, which impede the sustainability of its water resources and biodiversity. Climate change coupled with land use/land cover (LULC) change patterns account for most of the observed hydrological changes in the basin. The aim of this study was to assess the impact of changes in the climate and LULC on water resources in the basin, and its effect on the livelihoods of downstream users, particularly regarding water allocations. The water evaluation and planning (WEAP) model was applied to the assessment of runoff and streamflow and the percentage future water demand under climate change scenarios (RCP 2.6 and RCP 8.5), as well as the effects of current and future changes on water supply systems. LULC data from 1990 to 2019 were processed to detect the changes in LULC patterns in the basin. The results showed that from 1990 and 2019, the land use classes of settlements/bare ground, open savannah woodland, croplands, and waterbodies increased by 339.5%, 77.4%, 24.4%, and 607%, respectively. Close savannah woodlands, wetlands, and grasslands all decreased by 97%, 99.8%, and 21.2%, respectively. Overall, there was a significant difference in LULC changes. Hence, measures needed to be put in place to curb the changes, as the observed changes posed a serious challenge to the basin’s water resources. The results from the WEAP simulations also indicated that in the future, changes in discharge would be visible in September with ranges between 0.72 × 10⁶ m³ and 1.9 × 10⁶ m³ for RCP 2.6, and 0.65 × 10⁶ m³ and 2.5 × 10⁶ m³ for RCP 8.5, per month. Although the median values illustrate an increase in water availability from river discharge compared with the reference scenario, the uncertainties in future changes largely exceeded the predicted increases. Annual variability of the mean annual flows is projected to decrease over the period in the Black Volta Basin. Therefore, the outcomes of this study will be useful for different stakeholders within the basin in water resources planning and the formulation of appropriate policies for improving land use planning.