Analysis of the Hydrological Budget using the J2000 Model in the Pendjari River Basin, West Africa

Abstract

In a semi - arid region where water scarcity is a major problem, quantify the water balance variables is very essential for sustainable water management. In a condition where meteorological input data are often not available in a sufficient spatial and temporal resolution, simulating the water balance variables is a big challenge. This research assesses the water balance for the Pendjari River basin, a 23208 km² sub-basin of the Volta basin in West Africa. The main purpose of this study is to assess how much water is available in the Pendjari River basin in terms of blue water and green water. To assess the water balance variables the distributed hydrological model J2000 has been used. The model has been manually and automatically calibrated for the period 1982 – 1990 using 24 parameters and validated for the period 1998 – 2008. 17 of the parameters have been selected for regional sensitivity analysis. The performance of the model has been measured using objective functions: Root Mean Square Error, Percent Bias, Nash-Sutcliffe efficiency, Relative Nash-Sutcliffe efficiency and Coefficient of Determination. The findings of this study have indicated that 58.67% of annual rainfall represents the evapotranspiration, which is considered as the amount of green water used to support natural vegetation productivity and agricultural system. The total actual evapotranspiration is estimated at 87% of annual rainfall. 12.53 % of annual rainfall end up as surface runoff and 9.92% of annual rainfall represents the groundwater recharge rate. Approximately 21% of annual rainfall represents the water yield, which is devoted to blue water source in the Pendjari River basin. The meteorological simulations are globally acceptable and the hydro-meteorological component simulation has shown very good model performances in comparison with the observed discharge data, indicating the potential of J2000 model to reproduce the geographical environment of the Pendjari River basin.

Keywords: J2000; Green water; Blue water; Hydrological budget; Pendjari River