Utilization of Time-Based Meteorological Droughts to Investigate Occurrence of Streamflow Droughts

Abstract

Complexities of streamflow drought analyses motivate utilization of simple, alternative methods, which can provide timely information for effective water resources management. For this purpose time-based meteorological drought characteristics, identified by SPI 3−month , SPI 6−month and SPI Anuual 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 Anuual . The study area is the Doroodzan Watershed and Reservoir 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 Anuual 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 Anuual is based on one-year-ahead moving average rainfalls. Then, SPI Anuual of Jamalbeik station can be used to investigate occurrence of streamflow drought in Chamriz hydrometric station.

Probabilistic analysis of hydrological drought characteristics using meteorological drought

“…The proposed method to investigate these cross-dependencies differs from the few other attempts to connect these characteristics (e.g. Tabrizi et al 2010) by using precipitation deficit volume instead of SPI. The SPI has a valuable alert function, but because of the normalization, the index does not directly provide a measure of depth, which after the alert, is essential for water management.…”

“…For most of the raingauge and hydrometric stations, significant relationships were observed between time-based SPI values and streamflow drought intensities. For applicability reasons, comparisons and verification were confirmed against historical droughts (Tabrizi et al 2010).…”

“…Therefore, in this paper, we investigate, as an alternative, statistical relationships between hydrological drought and the preceding meteorological ones. This is not straightforward, because the characteristics for each drought type occur at different times and do not have similar sample sizes (Tabrizi et al 2010). Some early research by Santos et al (2001) made a comparison between computed hydrological (runoff) drought and meteorological drought.…”

“…This test was used to evaluate the relationships between corresponding drought types, based on ranked values (Tabrizi et al 2010). This method overcame the issue of different sample sizes for different drought types.…”

Comparability Analyses of the SPI and RDI Meteorological Drought Indices in Different Climatic Zones

“…The SPI has been used quite extensively, addressing a variety of drought related issues worldwide. Some of the more recent research efforts on SPI in Iran include and are not limited to; Morid et al (2006), Raziei et al (2009), Modarres (2010), Abolverdi and Khalili (2010) and Tabrizi et al (2010). As an alternative meteorological drought index, the reconnaissance drought index (RDI) was proposed by Tsakiris and Vangelis (2005), utilizing the ratios of precipitation over reference crop evapotranspiration (ET 0 ) for different time scales, to be representative of the region of interest.…”