5. CONCLUSION
The analysis of spatial pattern of drought using spatial SPI and temporal SPI from rainfall data is useful to determine the spatial distribution, characteristics of drought, evaluate drought affected areas and drought frequency in the Northeast of Thailand. By analyzing spatial pattern of rainfall data in the region was found that spatial pattern of mean annual rainfall for 29 years periods increased from the Southwest to the Northeast. A measurement of reliability of rainfall at each station for the study periods using CV analysis indicated that the high values of CV 6 months and 12 months were found in the Western part of the region. Multi-temporal SPI at various time scales was used to indicate drought occurrences at the station and its severity. From the observation of decadal variety of rainfall since 1976 by looking at number of dry rainfall station (SPI < -1) it was indicated that drought in the region was more severe in the 10 year period from 1988 to 1999. For spatial variation of drought in the region during the study periods, the most affected area of drought was found in the western and southern part of the region and its severity, which associated with the pattern of rainfall, decreased from Southwest to Northeast. The worst dry year
from spatial SPI was in 1979, 1981, 1986, 1997, and 2001 which drought affected areas are more severe and extend larger for SPI 6 months. The frequency, area extent and severity of drought assessed from SPI could benefit for sustainable water resources management and the development of mitigation strategies of drought events in the region.