The Impact of Climate Variability and Land Cover Change on Groundwater Resources in The Niger River Basin

Abstract

The Niger River Basin (NRB) has experienced severe droughts and floods under a significant change of the land use and land cover (LULC) with increasing population over the years. The present study is to understand the hydrological dynamics of NRB by using a water balance modeling approach with the seasonal variation of precipitation and LULC over the period from 2001 to 2013. The basin-scale NRB water balance model was then downscaled to the regional scale water balance model for two regions - Maradi and Zinder in Niger. Using the in-situ groundwater data, the decadal changes of groundwater depth in Maradi and Zinder were statistically analyzed to investigate the change of groundwater in the local level. The Zinder region was studied from 1999 to 2009, and the Maradi region was from 1995 to 2005. WetSpass was adopted for the basin-scale modeling of NRB, while its monthly simulator, WetSpass-M was used to simulate a regional water balance in Maradi and Zinder. The NRB water balance showed that the long-term average annual precipitation (735.09mm) was distributed as 48.10% (353.61 mm) for evapotranspiration, 6.27% (46.11mm) for interception, 45.69% (335.85mm) for surface runoff, and 10.53% (77.44) for groundwater recharge. For the study period from 2001-2013, the precipitation increased during the dry season by about 3%, but no significant change was observed during the wet season. The change in the LULC increased substantially in the areas dominated by agriculture, forests, and shrubs. . The regional groundwater study showed that the groundwater depth in the Zinder region decreased during both dry and wet seasons by 30% and 5%, respectively, while in the Maradi region, the depth of groundwater increased by 2% during the dry season and 3% during the wet season. Despite the increase in population density, irrigation for agriculture, and livestock over the study period, there was no significant change in the groundwater level. Our two studies show that precipitation is still the primary driver, followed by the LULC change and the soil texture that controlled the fate of water resources in the NRB and Niger.