Assessment and Application of Geostatistics in Identifying and Analyzing Drought Characteristics of Jazmourian Watershed

As one of the most important natural disasters “drought” is a phenomenon, which has an important impact on water resources, natural ecosystems and human societies economic, social, political and cultural from the point of view. Therefore, it is essential and inevitable to create a proper management system based on the recognition of the drought characteristics including frequency, severity, continuity and spatial extend, and its monitoring to reduce the damages and its consequences. In this study, with the aim of better understanding of droughts in Jazmorian watershed and recognizing dry and wet periods, eight special characteristics of drought were studied using the SPI and CZI Meteorological drought indices and Geographic Information System (GIS). For this the rainfall data of 24 rain gauge stations were used over a 30year period of 1983-2013 and the drought condition were assessed. In order to interpolate and prepare the most suitable zoning map for the studied features, Kriging, Co-kriging and Inverse Distance Weighted (IDW) methods were selected and compared. To select the appropriate model for fitting on the experimental variogram, the ratio of Sill to Nugget was used. To choose the right interpolation method, the mean absolute error (MAE), mean bias error (MBE), root mean square error (RMSE), and general standard deviation (GSD) were calculated then selected with lower values indicating stronger spatial structures. The results showed that in studying the majority of drought features, the co-kriging method was better than the other two methods, and the SPI index evaluated the drought condition in more detail than the CZI index. On the other hand, the Jazmourian watershed, especially in the eastern part of the province of Sistan- Baluchestan, has a relatively high sensitivity to the drought phenomenon, in which increases the frequency, continuity and severity of droughts to the eastern and southeast regions, and affect the inhabitants of these areas heavily by the consequences of the drought. Therefore, it is suggested that in macro planning and drought management plans for Jazmorian watershed, studying drought in different monthly and annual time scales and providing a suitable strategy for the management of drought in the highlands and plains areas separately.