Effect of Paddy Irrigation Water on Recharging Groundwater

Paddy irrigation water is well known as big contributor of groundwater recharge. During the irrigation season, large amount of water is kept in groundwater and some parts of it flow out to the main river directly or indirectly. The objective of this study is quantifying the effect of the paddy irrigation water on the groundwater recharge, and evaluating of the influence of the land use condition on the groundwater recharge. A comprehensive simulation model of groundwater flow in alluvial plain along Chikugo River, which is located in southwest in Japan, has been established by coupling GIS technique with traditional Finite Differential Model (FDM). In this study, relationships of groundwater level change and land use change were investigated. Using GIS, the fundamental data related to groundwater flow and land use conditions are input at every nodal point as database. A GIS based surface water simulation was carried out and spatial and temporal groundwater infiltration quantity is obtained and provided for groundwater flow simulation. Groundwater flows was calculated by adopting the Successive Over Relaxation (SOR) technique. The simulated result is consistent with the observed data, and the simulation model introduced in this study is fairly satisfactory. The result indicates that the paddy irrigation condition affects on the groundwater recharge. The simulation model introduced here is effective for quantification the groundwater recharge, considering the land use condition.