Methodology for assessment and forecast of drought severity based on the water balance analysis

Drought is a natural disaster which is hard to recognize its onset and termination and to estimate the damage from the events which occurred in the past and are expected in near future. While the drought indices or their frequencies are widely applied to explain the severity of each event in the existing studies, decision-makers and stakeholders (the public) may have trouble in understanding the results due to the unfamiliar expression with statistical values. In this study, therefore, the methodology for assessment and forecast of drought severity based on the amount of water shortage from the water balance analysis was be placed at the center of the discussion. Firstly, in order to improve the existing analysis for drought assessment adopted in the National Water Resources Plan, alternative methods have been suggested to estimate the amount of water demand in each sub-basin using the land use map, and in an aspect of water supply, reservoirs and underground water are included in the simulation of MODSIM-DSS. The relationship between drought severity from the simulated water shortage in the study area and the values of SPEIs (SPEI 6 = estimated for 6 months winter and spring season, SPEI 3 = estimated for 3 months summer season) has been analyzed by the Decision tree. Due to this achievement, at the end of the spring season, every year the forecast for the drought severity will be available with the quantitatively estimated water shortage, and it will be helpful to activate the drought mitigation measures before the disaster occurs.