Investigation of the relationship between hydrological and meteorological droughts at Maharloo Watershed, Fars Province

The current study aims to investigate the relationship between hydrological and meteorological droughts in the Maharloo Watershed, Fars Province. In order to assess the hydrological drought, Standardized Water-Level Index (SWI) was used, calculated from piezometric groundwater level data from 60 observation wells within 15 years (2000-2014). The Standardized Precipitation Index (SPI), calculated from the 15 years of rainfall data from 18 stations was used to assess meteorological drought in the study area. Two geostatistical techniques were employed to create drought zonation maps namely Inverse Distance Weighting (IDW) and simple kriging. Correspondingly, three criteria were chosen to evaluate the results including Mean Absolute Error (MAE), Mean Bias Error (MBE), and Root-Mean-Square error (RMSE). Furthermore, the Mann-Kendall test was used to assess the temporal trends of hydrological and meteorological droughts. As a result, trends in hydrological drought were increasing in a significant manner, while meteorological drought trend was decreasing at first and increasing afterwards so that it did not follow any particular trend. With regard to the results of hydrological drought assessment, the driest period has been occurred in 2000 with the SWI value of about 2.25, while 2003 had the highest SWI value equals -2.66 as the most significant wet period. Moreover,   the most intense drought and wet periods have been occurred respectively in northwestern and southwestern to central parts of the study area. The results of meteorological drought assessment indicated that the Komehr station has had the most intense wet period in 2000, however; it turned to have the most intense drought periods later on. As regards the evaluation of interpolation techniques, the IDW method with the lowest MAE value of 0.2688 and the lowest RMSE value of 0.0629was chosen as the best interpolation method compared to simple kriging. Also, the drought map obtained from the SPI method with the lowest values of MAE (0.2688) and MBE (-0.000051) found to be the most desirable method to assess the drought behavior in the study area.