Hydrological drought analysis of Yeşilırmak Basin of Turkey by streamflow drought index (SDI) and innovative trend analysis (ITA).

Drought is a natural disaster that has potential effects on the environment, life quality, water resources and economy. It has been clustered into 4 classes which are meteorological, hydrological, agricultural and socio-economic. Hydrological drought means reductions and deficiencies in the surface and ground waters that occur as a result of the long-term lack of precipitation. In this study, using the Streamflow Drought Index (SDI) and mean monthly streamflow data from 24 stations for the time scales of 1, 3, 6, 9 and 12 months, a hydrological drought analysis for the Yeşilrmak Basin of Turkey has been investigated. Being an extreme occurrence, droughts have been identified by their length of duration and severity. Finally, in order to more accurately and thoroughly assess the trends based on the classifications of dry and wet conditions, Innovative Trend Analysis (ITA) has been enhanced by the addition of 5 vertical and 5 horizontal lines, which constitute a novel side of the study. Results shows that the distribution of percentage drought occurance, wet categories are greater than drought categories. All throughout the basin, the mild drought class dominates with the highest occurrence percentages. Furthermore, according to evaluations of drought severity and duration, the longest-lasting drought—145 months—occurs in SDI-9 from 1997 to 2009, while the most severe drought—136.13—happens in SDI-12 from 2001 to 2009. Beginning around 2000, the region has been exposed to some of the longest-lasting and worst droughts ever recorded. By IDW, it has been analyzed that different parts of the basin are affected by droughts based on time scale while SDI-9 and SDI-12 show a similar distribution in drought and wet categories. According to ITA data, there is generally a trend in most drought time scale categories, and these trends have exhibited a majority of decreasing trend characteristics. [ABSTRACT FROM AUTHOR]