Abstract
Drought is a natural disaster that occurs globally when water availability is significantly below normal levels. Drought assessment is important for water resource planning, and therefore indexes can be used to characterize drought magnitudes. Using the monthly streamflow data at 47 stations from 1972 to 2011, the streamflow drought index (SDI) series with 3- (SDI-3), 6- (SDI-6), and 12-month (SDI-12) time scales were calculated, and the hydrological drought of the upper Tigris Basin in Turkey has been assessed. The results showed that almost all stations experienced at least one severe drought during the study period. The results revealed that since the early 1990s the study area has become drier. Using the data for a 12-month period and the area of the sub-basins for each flow monitoring station, area-weighted SDI-12 (WSDI) values were constructed. According to the WSDI results, the intensity and number of drought conditions increased during every 10-year period. This outcome has been verified using the maps of averaged SDI-12 values over the Tigris Basin. We noticed from observations of the maps that the time domain zones in lower latitudes experienced drought earlier as compared with zones in higher latitudes.
Highlights
Given the impact of climate change, hydrological extremes are occurring more frequently
The aims of this paper were to analyze the hydrological drought index based on the streamflow drought index (SDI) method for overlapping periods using 3-(SDI-3), 6-(SDI-6), and 12-month (SDI-12) time scales within each hydrological year, and to construct maps that indicated the averaged SDI-12 values over the basin for every 10-year period interval (1972–1981, 1982–1991, 1992–2001, and 2002–2011)
The probability distributions of log-normal and normal data were tested with the Kolmogorov–Smirnov test
Summary
Given the impact of climate change, hydrological extremes are occurring more frequently. Hydrological drought has had negative impacts on humankind’s water supply, ecological stability, and agricultural systems [2]. In terms of the four basic approaches to measuring drought, Wilhite and Glantz [7] categorized the definitions as meteorological, hydrological, agricultural, and socioeconomic drought. The first three definitions involve methods of measuring drought as a physical phenomenon, whereas the last definition involves tracking water scarcity and the effects on supplies through socioeconomic systems. Foremost among these definitions, hydrological drought is significant due to its high interdependence on processes such as the effects of urban water supply and hydropower generation on surface water resources [8]. Various drought indices that provide a quantitative method for determining drought events have been developed using hydrological variables
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