Temporal and spatial variations of precipitation trend in basins leading to Khuzestan province dust sources

Precipitation is the most important climatic factor affecting water supply and is one of the most variable meteorological phenomena. In order to study the precipitation trend in basins leading to the internal dust source of Khuzestan province, the gridded data of the National Iranian Drought warning and monitoring center with a grid resolution of 44km were used. This gridded data were made through reanalyzing daily, monthly, and yearly rainfall data from the synoptic, climatological, and meteorological stations of Meteorological Organization and the precipitation and evaporation stations of the regional water company, respectively using ArcGIS software. In order to study the decade by decade precipitation trend, 50 years precipitation data were used in form of five decades from 1968 to 2017, then spatial variations of precipitation in three basins of  Karun, Karkheh, and Zohre-Jarahi were detected by the zoning of the precipitation data and their maps were prepared. To detect the changes in time series of precipitation data, the homogeneity tests of Pettitt's were used, which is available in Excel using the XLSTAT statistical software. The result showed that there were two main precipitation cores in the Karun Basin in the fifth decade. The main precipitation cores of previous decades in the Karkheh and Jarahi-Zohre basins were weakened. The highest decrease in precipitation occurred in the downstream of the basins at the location of dust sources. Decade changes in precipitation showed that the decrease in rainfall started two decades ago in the three basins of Karun, Karkheh, and Zohre-Jarahi. This decline was clearly evident in the fifth decade and its harmful effects due to the increase in other parameters such as temperature and evaporation were doubled and contributed to the activation centers of dust.