ESTABLISHING SPATIAL DISTRIBUTIONS OF DROUGHT PHENOMENA ON CULTIVATION SEASONS USING THE SWAT MODEL

Due to global climate change, drought phenomena are becoming longer. As a result, water availability is insufficient to meet demand for agriculture during the cultivation seasons and many areas have affected by drought. These can cause difficulties in water resources management. The main objectives of this study were to establish the spatial distribution of drought phenomena at sub-basin scales in the Lam Khan Chu and Lam Nam Chi Part II watersheds, which is the major headwater of the Chi River Basin, Thailand. The Soil and Water Assessment Tool (SWAT) model was used to synthesize streamflow data at the sub-basins of the watersheds. To estimate drought severity, the Streamflow Drought Index (SDI) was computed from the time series of the synthesized streamflow data during 2008 to 2019. The simulated streamflow of the SWAT model was acceptable based on the R2, Nash -Sutcliffe Efficiency (NSE) and Percent bias (PBIAS) reaching good levels in both calibration and verification. According to the SDI calculation, the most severe drought in the study period was in the year 2016. During January and April of 2016, the affected areas of about 3%, 30%, 14%, 30 and 23% of the study area were identified as none, mild, moderate, severe and extreme droughts, respectively. The integration of the hydrological model and drought index to monitor drought severity in space and time will be a useful tool for assessing drought severity. Moreover, the results can support managers for water resources management.