Climate change impacts on water storage requirements of an agricultural reservoir considering changes in land use and rice growing season in Korea

Agriculture is directly affected by climate conditions and changes. It is necessary to understand the effects of climate change on agricultural water resources and to minimize its negative effects in order to achieve stable and sustainable crop production. Climate change affects not only crop water requirements but also various aspects of rice cultivation systems, including cultivation land and crop-growing season. This study aimed to analyze the impact of climate change on the water requirements of agricultural reservoirs using a reservoir water-balance model that includes climate change data, the paddy rice growing season and changes in land use. The results showed that due to increasing temperature, transplanting and heading dates were delayed 5–25 days and 0–10 days, respectively, in comparison to the baseline. The average decreasing rates of irrigation water requirements (IWRs) in eight districts were 7.0% (2025s), 9.2% (2055s) and 12.9% (2085s). The major causes of this decrease in IWRs were crop evapotranspiration and percolation followed by a shortened growing period. The average decreasing rates for yearly maximum water storage requirements in all reservoirs were 19.1% (2025s), 23.1% (2055s), and 26.9% (2085s). The decrease in rates could be the result of IWR and increasing watershed runoff (average 10.7% to 27.0%). The results of this study can be used to estimate the capacity and capability of agricultural water resources. Our results also contribute to the establishment of countermeasures against possible risks and the development of policies for future agricultural water management.