The evaluating of drought zoning models in various time scales case study: Sistan and Balouchestan Province

Drought is a creeping natural hazard with large extent of occurrence, causes considerable damages to different economical parts of our country. Because of the vast impact of drought, it is essential to be monitored timely and spatially. Specifically, SPI was used as drought monitoring Index of Sistan and Balouchestan province of Iran, and for zoning proposes three models (Kriging, Spline and IDW) were employed. Results showed that during last 25 years period (1981-2005), occurrence of drought has been more frequent and also lasted longer than the early years. However, the severity of drought has been reduced. It can be seen that the duration and severity of drought is more in the southern and central area than in the northern parts of the province. Cross validation technique with R2, RMSE, MDE and MAE were analyzed to assess the zoning methods. Results of ranking these criteria’s summation showed that the Kriging with Gaussian variogram, with RMSE, MDE, MAE and R2 equal to 0.546, -0.0015, 0.42 and 0.56 (the maximum correlation), respectively, and the IDW with 1 and 2 power were the best methods for drought zoning. Finally, drought’s severity maps were generated, which are useful tools to take management decisions to solve the drought crisis problems.