Assessment of Future Climate Change Impact on Agricultural Water Supply Capacity in Geum River Basin Using SWAT and MODSIM-DSS

Abstract

This study is to evaluate future agricultural water supply capacity in Geum river basin (9,865 km²) using SWAT and MODSIM-DSS. The MODSIM-DSS was established by dividing the basin into 14 subbasins, and the irrigation facilities of agricultural reservoirs, pumping stations, diversions, culverts and groundwater wells were grouped within each subbasin, and networked between subbasins including municipal and industrial water supplies. The SWAT was calibrated and validated using 11 years (2005-2015) daily streamflow data of two dams (DCD and YDD) and 4 years (August 2012 to December 2015) data of three weirs (SJW, GJW, and BJW) considering water withdrawals and return flows from agricultural, municipal, and industrial water uses. The Nash−Sutcliffe efficiency (NSE) of two dam and three weirs inflows were 0.55∼0.70 and 0.57∼0.77 respectively. Through MODSIM-DSS run for 34 years from 1982 to 2015, the agricultural water shortage had occurred during the drought years of 1982, 1988, 1994, 2001 and 2015. The agricultural water shortage could be calculated as 197.8 × 10⁶ m³, 181.9 × 10⁶ m³, 211.5 × 10⁶ m³, 189.2 × 10⁶ m³ and 182.0 × 10⁶ m³ respectively. The big shortages of agricultural water were shown in water resources unit map number of 3004 (Yeongdongcheon) and 3012 (Geumgang Gongju) areas exceeding 25.1 × 10⁶ m³ and 47.4 × 10⁶ m³. From the estimation of future agricultural water requirement using RCP 8.5 INM-CM4 scenario, the 3004 and 3012 areas showed significant water shortages of 26.1 × 10⁶ m³ (104.1%) and 50.9 × 10⁶ m³ (107.4%) in 2080s (2070∼2099) compared to the present shortages. The water shortages decreased to 23.6 × 10⁶ m³ (94.0%) and 43.3 × 10⁶ m³ (91.4%) below of the present shortages by developing irrigation facilities.