Evaluation of effect of the upland field on the groundwater recharge

The objectives of this study are quantification of the upland field effect on the groundwater recharge and evaluation of the influence of the land use condition on the groundwater recharge. The groundwater analysis is conducted using MODFLOW in a 1540 ha study site, Izena Island, which is located in southwestern Japan. To specify the initial and surface boundary condition, data on the elevation and use condition in the study site stored in the GIS database is transferred into the numerical model of groundwater flow, respectively. To quantify the upland field effect on the groundwater recharge, the groundwater analysis is conducted in 2 cases. First, the groundwater storage is calculated under the present land use condition. Next, the groundwater analysis is conducted when all forests in the study site are converted into the upland field. Simulation results indicated that groundwater storage, when all forests are converted into the upland field, is larger than the groundwater storage under the present land use condition. This result is caused that the irrigation water in the upland field contributes to the ground water recharge and the water loss by the rainfall runoff and the evapotranspiration at the upland field is less than amount of the forest.