Maryam Daemi; Amirreza Keshtkar; Saeed Bazgeir; Ali Afzali; Omid Kavoosi
Abstract
Hydrological drought is used to show the reduction of surface flows and the drop in the level of underground water reservoirs, lakes, and rivers. The present research was carried out to determine the basic flow index values and to check its efficiency in determining the type of flow regime and regional ...
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Hydrological drought is used to show the reduction of surface flows and the drop in the level of underground water reservoirs, lakes, and rivers. The present research was carried out to determine the basic flow index values and to check its efficiency in determining the type of flow regime and regional analysis of hydrological drought in the Halil-Rood watershed. For this purpose, three homogeneous hydrological drought zones were determined based on the threshold level and cluster analysis, and then the base flow index was calculated on a daily scale using the daily discharge data in 10 hydrometric stations in the homogeneous zones. The results showed that the regional average of the annual base flow index is 0.38 with a standard deviation of 0.193 in the long-term statistical period and the range of the base flow index is 0.12-0.29. Based on the 70th, 80th, and 90th percentiles, the river flow regime was divided into four classes, and it was found that 100% of the watershed sub-basins of the study area had an unstable regime. Also, the results of drought zoning showed that hydrological drought occurred at the threshold level of 70 in the southeast of the region in the area of the Dehroud hydrometric station and in the levels of 80 and 90 in the northwest of the region in the area of Baft and Cheshme-Arus stations. The results of the present research can be used in the assessment of underground water supply, water supply systems, irrigation management, hydrological drought monitoring, and regional models in the estimation of water resource reserves in areas without statistics.
Kazem Nosrati
Abstract
The term hydrological drought is applied to represent low water levels in streams, reservoirs and lakes as well as a low groundwater level. Base flow index (BFI) as one of low flow indices gives the ratio of base flow to total flow and investigates basin’s ability to store and release of water in drought ...
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The term hydrological drought is applied to represent low water levels in streams, reservoirs and lakes as well as a low groundwater level. Base flow index (BFI) as one of low flow indices gives the ratio of base flow to total flow and investigates basin’s ability to store and release of water in drought periods. The objectives of this study were to determine BFI and to validate this index in drought studies of Sefidrood Drainage Basin. To view of this, first three homogenous regions were identified based on the threshold level using cluster analysis. Then, daily BFI was calculated in 28 gauging stations of the homogenous regions. The results showed that the regional mean of BFI with value of 0.65 (SD=0.19) is stable during long-period data. BFI ranged between 0.17 and 0.86 and also based on the 25, 50 and 75 percentiles, river flow regime in the study area is divided into four categories that show more than 50 percent of the catchments in the study area have low or unstable regime. So it would be hard that the catchments able to provide river flow during drought periods. Therefore the results of this study can be used in assessment of groundwater recharge, water supply system, irrigation management, and hydrological drought monitoring as well as regional modeling of water resources storage and hydrological drought in ungauged areas
