Abstract
The Nasia catchment is the reservoir with significant surface water resources in Northern Ghana and home to numerous subsistence farmers engaged in rainfed and dry season irrigation farming. Yet, there is little understanding of the hydro-climatic and land use/cover conditions of this basin. This study investigated trends, relationships and changes in hydro-climatic variables and land use/cover in addition to implications of the observable changes in the Nasia catchment over a period of 50 years. Parameters used for the study were minimum (Tmin) and maximum temperature (Tmax), wind speed (WS), sunshine duration (S), rainfall (R), relative humidity (RH), discharge (D) and potential evapotranspiration (PET) data, 15 years of remotely sensed normalized difference vegetation index (NDVI) data and 30 years of land use/cover image data. Results show that Tmin, Tmax, WS and PET have increased significantly (p < 0.05) over time. RH and S significantly declined. R, D and NDVI have not decreased significantly (p > 0.05). A significant abrupt change in almost all hydro-climatic variables started in the 1980s, a period that coincides with the occurrence of drought events in the region, except WS in 2001, R in 1968 and D in 1975, respectively. Also, D showed a positive significant correlation with RH, R and PET, but an insignificant positive relationship with S. D also showed a negative insignificant correlation with Tmin, Tmax and WS. Areas covered with shrubland and settlement/bare lands have increased to the disadvantage of cropland, forest, grassland and water bodies. It was concluded that climate change impact is quite noticeable in the basin, indicating water scarcity and possibilities of droughts. The analysis performed herein is a vital foundation for further studies to simulate and predict the effect of climate change on the water resources, agriculture and livelihoods in the Nasia catchment.
Highlights
Climate change presents the most pressing challenge of the twenty-first century, with extraordinary impact on natural ecosystems, economic sectors, society and water resources (Arnell 2004; Khaliq et al 2009; Sabbaghi et al 2020; de Hipt et al 2018; Schilling et al 2020; Baarsch et al 2020)
Bare areas were combined with settlement due to the dryness of the basin located in the Guinea Savannah zones
The findings show that potential evapotranspiration in the Nasia basin has significantly increased over the last 50 years
Summary
Climate change presents the most pressing challenge of the twenty-first century, with extraordinary impact on natural ecosystems, economic sectors, society and water resources (Arnell 2004; Khaliq et al 2009; Sabbaghi et al 2020; de Hipt et al 2018; Schilling et al 2020; Baarsch et al 2020). Variations in climatic conditions are important determinants of vegetation growth and density across the world and, especially, in tropical and subtropical Africa (Warburton et al 2012; Schmidt et al 2014). Feedbacks from land surface processes and vegetation dynamics influence local and regional climate variability. Vegetation, are likely to aggravate the climate change situation in a way that the hydrological cycle will be altered, resulting in an increase in frequency and severity of droughts and floods which in turn influences agriculture, water supply, environmental sustainability and protection from floods (Aduah et al 2018). The combined effects of climate variability, land use/cover changes and unsustainable water management practices have led to a significant alteration in the water balance of the river basins (Buma et al 2016). Unsustainable land use/cover activities, affect soil structure, texture and fertility that play a key role in food production (Lal et al 2015)
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