Document Type : Research Paper
Authors
1 Soil Conservation and Watershed Management Research Department, Khorasan Razavi Agricultural and Natural ResourcesResearch and Education Center, AREEO, Mashhad, Iran
2 Associate Professor, Soil Conservation and Watershed Management Research Department, Khorasan Razavi Agricultural and Natural ResourcesResearch and Education Center, AREEO, Mashhad, Iran
3 Assistant Professor, Soil Conservation and Watershed Management Research Department, Khorasan Razavi Agricultural and Natural ResourcesResearch and Education Center, AREEO, Mashhad, Iran
Abstract
Drought propagation refers to the transmission of moisture deficits from meteorological to hydrological drought, representing a central issue in water resource management in arid and semi-arid climates. This study was conducted to analyze the spatial propagation of drought and examine the role of environmental characteristics in Khorasan Province. Meteorological and hydrological droughts were identified using the Standardized Precipitation Index and Standardized Streamflow Index , Drought events were extracted using a threshold of ≤ -1, and paired events were determined. For each event, the severity and intensity of meteorological and hydrological droughts were calculated, followed by the derivation of propagation ratios for severity and intensity and their normalized versions. A set of physiographic and climatic variables including slope, NDVI, precipitation seasonality index , snow fraction , aridity index , and available water capacity were extracted as basin-wide averages and subjected to correlation analysis.Spatial analyses revealed that the mean severity of meteorological drought ranged from 0.23 to 2.17, with an approximate average of 2.1, whereas hydrological drought severity ranged from 0.14 to 1.16, with a mean of 0.65. The coefficient of variation for hydrological drought severity was approximately 63%, compared to 37.7% for meteorological drought severity, indicating greater spatial variability in hydrological drought. At the basin scale, 54% of basins exhibited a decrease in severity propagation, and 67% showed a decrease in intensity propagation, with mean severity and intensity propagation ratios of -0.03 and -0.1, respectively. This pattern reflects a general attenuation of drought effects as they transition into hydrological systems. Significant negative correlations were observed between meteorological drought characteristics and propagation ratios for severity and intensity (-0.48 and -0.67, respectively), indicating that meteorological events with higher severity and intensity tend to experience greater attenuation during propagation. In other words, high-intensity atmospheric drought does not always translate into corresponding hydrological drought severity.
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