Abstract

A drought is a multi-dimensional event characterized by changes in the atmospheric and land conditions. Hence, monitoring a single drought indicator may be insufficient for water management. The hybrid drought index (HDI) is presented as a nonparametric composite indicator for monitoring multiple components of the hydrologic cycle. The properties of the HDI can be summarized as follows: (1) HDI describes drought indicated from either climatic anomalies or available water (AW); (2) HDI describes the drought onset as early as a decrease appears in climatic variables, while it shows drought persistence until there is no longer a terrestrial deficit; and (3) HDI shows a more severe drought condition when both the climatic water balance and AW exhibit a deficit. HDI is based on the states of potential meteorological water budget and AW. The proposed integrated drought-monitoring is applied to the Zayandehrud River Basin of Iran to show the status of components and depict drought propagation through each one from climate to groundwater. Finally, HDI announces the general status of the hydrologic cycle. A monitoring system established based on HDI would also allow the managers, local businesses, and farmers to identify the status of water supply capacity and water availability.

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