Future hydrological drought hazard assessment under climate and land use projections in Upper Nan River Basin, Thailand

摘要

Drought has extensively affected Thailand because agriculture is an important source of the country’s income. Upper Nan River Basin (U-NRB) is an important basin for agriculture in Thailand. This research studies future drought hazard in U-NRB under climate and land use change projection by considering into three future period: 2020s (2011-2040), 2050s (2041-2070) and 2080s (2071-2100). This study analyzed the drought hazard under three parameters that are the standardized precipitation-evapotranspiration index (SPEI), Streamflow Drought Index (SDI), and ground water yield. The three Regional Climate Models (RCMs) are used to compute and figure out the SPEI under two Representative Concentration Pathway (RCP4.5 and 8.5). The SDI is calculated from future streamflow data which obtain from hydrological model. The weighting factors of each drought parameter are efined with Analytic Hierarchy Process (AHP). SPEI has more significant effect than SDI and ground water yield. Moreover, the drought period depends on standing shortage of rainfall at 1, 3, and 6 months. The future drought hazard maps are displayed as drought hazard levels which are very low, low, medium, and high. The results found that SPEI1 and SPEI3 under RCP4.5 and 8.5 change from very low to low, low to medium and medium to high but they do not change much in 2050s for RPC4.5. For SPEI6, the results show that drought hazard level has trended to decrease severity under RCP4.5 both in 2050s and 2080s but the drought hazard level under RCP8.5 has trended to increase severity as medium and high in 2050s and 2080s. Therefore, Most of the areas in U-NRB are low and medium hazard level in 2050s. Whereas, medium and high hazard levels are found in the U-NRB in 2080s.