SPATIAL MODELING OF GROUNDWATER RECHARGE USING SWAT MODEL IN R'MEL AQUIFER (NORTHWESTERN OF MOROCCO)

The estimated groundwater recharge presented in this research paper is modeled by the water balance approach, and then incorporated into SWAT model. This semi-distributed physical model provides a dynamic estimate of recharge. The SWAT model has been proven to provide a powerful tool for estimating recharge, runoff and erosion on a daily, monthly or annual time step. The value of this type of analysis lies in its ability to simulate in a reasonable manner the physical processes that control the groundwater recharge by rainfall. Meteorological parameters such as temperature, rainfall and solar radiation are taken into account, as well as soil properties, slope and landuse. In this study, the results of several analyzes using SWAT, were used to develop an empirical relationship between annual rainfall and the amount of recharge that is likely to occur. Groundwater recharge is not a constant as previous studies have suggested, although the long-term mean can be estimated, if an annual average rainfall is assumed. For long-term of 752 mm average rainfall, this study suggests a 237 mm average recharge. The water balance is calculated using the annual average values from the output files of the SWAT model. In general, the results show that evapotranspiration is the main component of annual water balance for the study area, SWAT estimates that evapotranspiration is 52% (395 mm) of total rainfall, more than half of the precipitation is lost due to evapotranspiration. Runoff accounts for nearly 10% of the water balance (73 mm). The mean annual infiltration is estimated at 283 mm / year, representing almost 38%.