Utilization of Time-Based Meteorological Droughts to Investigate Occurrence of Streamf low Droughts

摘要

Complexities of streamflow drought analyses motivate utilization of sim-ple, alternative methods, which can provide timely information for effective water resources management. For this purpose time-based meteorological drought char-acteristics, identified by SPI_(3-month), SPI_(6-month) and SPI_(Amuual) are investigated. A boxplot approach is used to exclude non-rainy months from the analysis. Streamflow drought characteristics are described by drought intensities, and are calculated by the threshold level method. The non-parametric Wilcoxon-Mann-Whitney test is used to investigate relations between streamflow drought intensities and SPI_(3-month), SPI_(6-month) and SPI_(Amuual), The study area is the Doroodzan Watershed and Reser-voir in southwestern Iran, with four rain gauge and two hydrometric stations. According to the results, most of time-based SPI values show significant relations (at 5% level of significance) with streamflow drought intensities. However, the most significant relation is between SPI_(Amuual) of Jamalbeik rain gauge station (centrally located in the study area) and drought intensities of Chamriz hydrometric station (located at the reservoir inlet). Comparison of study results with available records of documented droughts, confirms applicability of the proposed procedures. The SPI_(Amuual) is based on one-year-ahead moving average rainfalls. Then, SPI_(Amuual) of Jamalbeik station can be used to investigate occurrence of streamflow drought in Chamriz hydrometric station.