[A-HW24] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW24-16] Variation Of Water Balance Components in the Kurose River Basin Between The 1980s and 2000s Using SWAT

*Sharon Bih Kimbi¹, Kunyang Wang¹, Shin-ichi Onodera², Ichirow Kaihotsu¹, Yuta Shimizu³, Yusuke Tomozawa² (1.Graduate School of Integrated Arts and Sciences, Hiroshima University, 2.Graduate School of Advanced Science and Engineering, Hiroshima University, 3.Western Region agricultural Research Center, National agriculture and Food Research Organization)

Keywords:Groundwater, Kurose River basin, Landuse change, Water Balance, SWAT

Hydrologic models have been used to evaluate water availability and determine long-term sustainable water resources management policies through a comprehensive assessment of all water cycle components. The Kurose River Basin with a total area of 39.95km2 has undergone the cumulative effects of increased population and land-use change which has pressured the availability of groundwater resources in it its watershed. The study was aimed to analyse the impact of land-use change on groundwater using the SWAT model. This is a physically-based semi-distributed hydrological model with various applications to simulate water balance and watershed management. Daily discharge records for 1980-1993 and 2000-2007 with land use data for 1987 and 2009 were used in this research to compare the water balance between the 1980s and 2000s, emphasising groundwater recharge. The results showed that the calibration and validation exhibited satisfactory criteria for hydrologic simulations with both NSE and R² coefficients greater than 0.55. Simulation results showed that land-use changes have resulted in a corresponding increase in surface runoff and a decrease in groundwater recharge from the 1980s to the 2000s. Also, paddy areas were observed to be high groundwater recharge zones but due to urbanization processes, these areas have been encroached thus leading to a decrease in groundwater recharge in the recent historic years.