Numerical Assessment of Hydrodynamic Trends and Groundwater Recharge through Long Chronicle Data in the Bagré Dam, Burkina Faso: Implications for Climate Change and Dam Management Operations

Abstract

In the context of climate change and the subsequent pressure of human activities, there is abounding need to establish a clear relationship between reservoir storage, rainfall, and groundwater recharge in Bagre dam, Burkina Faso. Hydrodynamic variables collected in and around the operations of Bagré dam (e.g., evaporation, inflow, irrigation, spillage, water level, rainfall) were analysed, using the singular spectrum analysis to delineate the trends and variability over the 1993-2022 period. Additional sensitivity assessments were conducted on groundwater data between 2002 and 2022, using linear and polynomial models to predict the impact of the reservoir water level on the groundwater; Pettitt and Mann Kendall test to evaluate the significance level of the trends and a water table fluctuation and infiltration models were developed to delve into the influence of the reservoir water level and rainfall on groundwater recharge in and around the Bagré Dam. The result shows that there is an increasing trend of spillage due to increasing inflow. Evaporation trend is decreasing, and irrigation trend is increasing. Rainfall trend is decreasing from 2012, and the reservoir water level is relatively stable. The statistical indices showed strong, moderate, and very low relationship with the water level. The percentage of groundwater recharge percentage is between 25-28%, which is stable due to the constant availability of surface water. The Mann Kendall and Pettitt tests show an increasing trend and breaking points on most of the piezometer profiles. Inflows rise has affected the dam stability while spill over led to flooding downstream of the Bagre Dam. The reservoir water level is improving the groundwater recharge, which will enable agricultural practice irrespective of the seasons around the dam. These results suggest that future ground water trends and variability in and around the Bagré Dam can be predicted using the variables from dam management operations.