Drought analysis with standart drought indices: The case of Konya closed basin

The accelerating increase in the world population and the parallel decrease in natural resources make it necessary to use the existing resources with maximum efficiency. Drought occurs when the amount of water in a region decreases after various meteorological, hydrological, geological and sociological events such as insufficient precipitation, evaporation, changes in geological structure and human factors. There are various drought indices in the literature on drought, which are based on mathematical and statistical equations and use data such as precipitation, temperature, evapotranspiration, etc. In our country, there are drought analyzes carried out with drought indices. In this study, drought analysis was carried out in Konya Closed Basin where drought is intensely observed with three different drought indices (Standardized Precipitation Index, Standardized Streamflow Drought Index, Standardized Groundwater Index) using data from precipitation, streamflow and well observation stations. The aim of the study is to present a comparative drought analysis for Konya Closed Basin with up-to-date data and as many observation station data as possible. In addition, the necessity of subtracting the trend component of groundwater levels, which have a significant decreasing slope especially in recent years, instead of using them directly in the calculation of drought index has been revealed. In these calculations, the Hydrological Relative Strength Index method proposed for the first time in the literature was used. In the comparative analysis made with the three indices, it was observed that precipitation, flow and groundwater droughts follow the same course, in other words, dry and non-dry periods follow each other in harmony. However, the study concluded that while there is no clear trend in precipitation-related drought, there is an increase in flow and groundwater-related drought, and that flow and groundwater droughts last longer than precipitation. It is also observed that the proportion of very severe drought classes in stream and groundwater is significantly higher than in precipitation, and moderate and severe drought classes vary more for stream and groundwater on a station basis compared to precipitation. This conclusion reveals that drought in runoff and groundwater is more variable than precipitation and should be evaluated with a separate importance in terms of its impact. It also indicates that short-term but severe single droughts in the region during the dry period may be more effective and dangerous in water-related sectors, especially in agriculture.