Spatial Drought Risk Assessment Using Standardized Precipitation Index and Effective Drought Index: Edwards Aquifer Region

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2015-01-20

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Though drought is a recurrent natural disaster in Texas, little attention has been so far paid to the preparedness of drought for spatial drought risk assessment. This study presents a methodology for spatial assessment of drought hazard, vulnerability, and risk in the Edwards Aquifer (EA) region. A conceptual data-based framework for drought hazard and vulnerability was developed in this study. Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) methods were used to identify Drought Hazard Index (DHI) in different time steps, while the GIS environment was used to map the spatial extents of drought hazards. Drought Vulnerability Index (DVI) was identified by using different social and physical consequences of drought and a thematic map was prepared on the county level for vulnerability assessment. The risk, as a result, was computed as the product of intersection between both the DHI and DVI. Very high drought risk was found by 9 and 24-month SPI and EDI in Bexar (9.8% of the area). The highest percentage of the area in high level drought risk was detected by 1 and 12-month SPI as 32.3% of the area and 3-mont SPI found the highest moderate percentage of the area (79.5%). Bexar was found under drought risk based on all time scale SPI and EDI (very high drought risk based on 9, 24-month SPIs and EDI). Medina, furthermore, was detected in high drought risk in terms of all time scale SPI (except 3-month SPI) and EDI. In general, drought risk is higher in counties of the southern part of the area. The results confirmed that higher drought risks are found where both high hazard and high vulnerability coincide.

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