Abstract
The main purpose of this study is to analyze the effects of climate change on drought levels in the future by using both hydrological model (SWAT) and Standardized Precipitation Index (SPI) tools. Three benchmark periods of climate change were used for simulation such as 2010-2039, 2040-2069 and 2070-2099. These results were then compared with the baseline period (1980-2009) at nine zones in the basin. Results indicated that both the SWAT model and SPI index showed a similar correlation in duration and density of the drought occurrence levels based on shortage of soil water content and values of drought index through climate change effects. These impacts include not only temporal changes, but also spatial changes, in the future. Results also reflect that the soil water shortage and values of SPI index also showed significant reductions in April, May and November. Most of the severe droughts seem to increase in intensity in two of these months, specifically those that appeared in April in five sub-basins and in November in six sub-basins during the period of 2010-2039; drought in April appeared in four sub-basins and drought in November in six sub-basins in the period of 2040-2069; severe drought occurred in nine sub-basins in April and seven sub-basins in November during the period of 2070-2099. The results suggest that the drought occurrence levels have a trend of increased severity from the North to the South and gradually reduced from the East to the West in May, but then the drought severity increased in the middle of basin with the trend from the South to the North in November. The methods applied in this study are expected to be appropriately applicable to the evaluation of the effects of extreme hydrologic events, and this study can provide useful values for sustainable water-resource management strategies and policy in agricultural basins.
Key words: Hydrology model, standardized precipitation index, climate change, soil water content drought levels.
