Hydrological drought analyzing and monitoring by using Streamflow Drought Index (SDI) (case study: Lorestan, Iran)

In the presented study, the hydrological drought continuity and severity in Lorestan province, Iran, was investigated by employing the Streamflow Drought Index (SDI). The SDI method is a technique for prediction of the drought onset and its duration. This method uses the cumulative flow rate of the river as well as the spatial extent of drought for assessing and monitoring the hydrological droughts. Four different periods of 3, 6, 9, and 12 months were investigated in this study of the selected location. The required data were gathered from ten hydrometric stations for a 32-year period between 1984 and 2016. To normalize the hydrometric stations' discharge data, a normal probability distribution was used at a confidence level of 10% by exerting the Kolmogorov-Smirnov test (K-S). Furthermore, by applying the IDW method in the Arc GIS software, the drought zoning from 2005 to 2016 was mapped for the mentioned periods. The results of SDI showed that all the hydrometric stations in the considered location have experienced at least one severe drought. Most parts of the region, we affected by the drought for 11 years during 2005 to 2016. These results are consonant with the discharge values in the same period. Finally, based on the zoning results, it was found that in most parts of this region, the rivers stream flow was in the mild to moderate levels.