Comparison of Standardized Runoff Index and Apportionment Entropy in Hydrological Drought Analysis of Susurluk Basin Flows

Hydrological drought is one of the most essential natural hazards attributing water scarcity and its global impact increases due to the climate change. In particular, the usage of climate models and rainfall-runoff models for projecting the severity of future drought has become a popular issue in the hydrology literature. In this context, the primary analysis of the data monitored in the past period is surely the basis of projection studies. In the study prepared, hydrological drought analysis based upon two different indices have been applied to ten annual mean natural flow data obtained from streamflow gauging stations located at Susurluk Basin for 1981-2010 water year period. In the implementation phase, standardized runoff index (SRI), which was formerly used in terms of its practicality and prevalence, and relatively recent one termed as apportionment entropy (AE) were comprehensively compared. When proportional distributions pertaining to dry, wet and normal climatic characteristics, which were derived from SRI analysis, was considered, it was detected that AE approach was not such a suitable approach in the monitoring of long-term hydrological drought.  When the same method was taken as a reference, it was determined that the drought classification being close to almost normal severity was prominent over the basin. Once the results of trend analysis exposed to standardized index values were also taken into account, the trend structures encountered in the drought frequencies have pointed out that activities of both semi-arid and extreme arid periods may increase in the near future.