Integrated Seasonal Drought Risk Assessment Under Climate and Land Use Changes for Agricultural Areas Upstream of Pasak Reservoir, Thailand

Most previous drought risk assessments have been done on monthly or annual time-scales, which do not directly correspond to crop conditions during wet and dry seasons. To address this limitation, this study introduces a novel framework for seasonal drought risk assessments. The analysis is conducted across multiple temporal periods, including the past (2020s: 2001–2020), near future (2030s: 2021–2040) and far future periods (2050s–2090s: 2041–2100) while considering the combined impacts of land use and climate change scenarios RCP4.5 and RCP8.5. Multi-drought hazard indices were developed to characterize drought conditions and evaluated for dry seasons (November to April) and wet seasons (May to October). Groundwater storage outflow was incorporated into the analysis to reflect its critical role as an alternative water source. Under RCP8.5 in dry seasons, the results show a decrease in drought risks from very high to high from the 2030s to the 2070s followed by an increase toward the 2090s. Meanwhile, in wet seasons under RCP8.5, the results exhibit an increase from very low to low for the 2030s–2090s. Adoption of drought-resistant crop varieties and improvement of irrigation systems in irrigated areas, as well as adaptive irrigation management in non-irrigated areas, were found to reduce drought damage in the future.