| dc.description.abstract | Because of significant rainfall discrepancy between wet and dry seasons, difficulties in developing new water resources, serious sedimentation in reservoirs, increases in water demand and so on, effective management of water resource become an important issue in drought periods. Therefore, effective drought early warning is critical to provide drought information to help government agencies for decision making and to reduce impacts to economics, society, and agricultures. In this study, BMDI (Bhalme and Mooley Drought Index), PDSI (Palmer Drought Severity Index) and SWSI (Surface Water Supply Index) were used to access the meteorological, agriculture and water resources droughts, respectively, in association with statistical downscaling climate forecasts from the Central Weather Bureau to provide drought early warning as references for responses and decision makings.
The study area is the water supply district of the Shihmen reservoir. Both meteorological and hydrological data from 1976 to 2010 were used to calculate the three drought indices for the study area to examine whether past drought events can be captured by these indices. Severe droughts in year 2002 and 2003 were used to investigate our approach of combining drought indices with climate forecasts. A weather generator was used to provide daily rainfall and temperature to drive a hydrological model to obtain daily inflow of the Shihmen Reservoir. Then a system dynamic routing of reservoir operation was used to calculate the daily reservoir storage. Based on drought indices calculated with a lead-time of three months, strategies for reducing water supply in association with different drought severities were proposed.
Based on results in this study, the BMDI is easy to be affected by rainfall and drought duration predicted by the BMDI is shorter than the real cases. After extreme rainfall events, the starting time of agricultural drought predicted by the PDSI is lagged. Due to small reservoir capacity in the Shihmen Reservoir, onsets of droughts predicted by the SWSI were similar to those by the other two indices. By combining statistical downscaling climate forecasts and drought indices, the water reduction strategies proposed in this study can effectively mitigate drought severities and reduce amount of fallow compensation. With advantages of climate forecast, the drought early warning is ready to support decision making for water resources allocations and responses measures. | en_US |