Hydro-climatic and Water Availability Changes and its Relationship with NDVI in Northern Sub-Saharan Africa

The variations in total water storage anomaly and groundwater balance were examined during 2002-2016. Based on the empirical orthogonal function, it was found that the water resource underwent high variability. The linear trend of hydro-climatic variables, total water storage anomaly, water budget, and its components have been investigated. For the area average, all the variables increased except for the potential evapotranspiration, which had decreased during the period of study. For the spatial distribution of trends in total water storage (TWS) in the northern Sub-Saharan Africa (NSSA), 44.76% underwent significant negative changes, whereas the proportion of areas that underwent significant negative changes was 24.84%. The results indicated that the precipitation and soil moisture were determinant factors for positive changes in TWS, whereas the potential evapotranspiration and temperature contributed to the reduction in TWS, respectively, implying a harmful effect of rising in temperature on water resources over the region. Moreover, a non-significant positive interdependence between the area-averaged TWS and the water budget (WB) was acquired. Positive correlations between normalized difference vegetation index (NDVI) and TWS (WB) occupied 48.93% (37.86%), but negative correlations occupied 34.59% (28.49%) of the total area. Results of the relationships between TWS and NDVI were higher than that of NDVI and water budget over the period 2002-2015. The TWS and WB (water resources) played essential roles in the positive changes in the ecosystem. These findings are valuable for the management of agriculture, water resources, environment, and ecosystem, profiting from the implementation of policies at regional and local scales.