Author(s): Kozue Yuge, Mitsumasa Anan, Kosuke Hamada
Linked Author(s): Kozue Yuge
Keywords: Groundwater storage, multi-functionality of agriculture, land use condition, surface water balance, water demand
Abstract: The aim of this study is quantifying irrigation effect on the groundwater recharge in crop fields of the subtropical island, Izena (N24? 55', E127? 56'), which is located in southwestern Japan. Izena Island is relatively plain and the soil of this island is classified as the special red-yellow clay soil (called Kunigami Maaji). This soil is acidic, and the hydraulic conductivity is high. The staple crop in this island is sugar cane and land use conditions can be categorized as the crop field, forest and artificial surface. In crop fields, a large amount of water is irrigated for not only supply water loss of evapotranspiration but also various purposes, for example, protection of salt breeze damage or leaching. Since main water resource for irrigation is dependent on groundwater in the study site and there is a serious risk of drought, subsurface dams have been constructed to supply the agricultural water and it is important to evaluate the groundwater movement to develop the subsurface dams, considering the land use condition and agricultural water use. The groundwater analysis was performed using MODFLOW in a subtropical island which is located in southwestern Japan. To simulate the groundwater flow, surface water balance in each land use condition was estimated in the study site. Boundary conditions were specified using elevation, surface water balance and sea water level. Scenario analysis was performed to evaluate the effect of irrigation water of crop fields on groundwater recharge under several assumed land use conditions. The results indicated that the irrigation water in crop fields contributed to the groundwater recharge and the water loss by the rainfall and the evapotranspiration in the crop field was less than the amount of that in the forest
Year: 2017