Development of Community Water Deficit Index: Drought-Forecasting Tool for Small- to Mid-Size Communities of the Southeastern United States

Abstract

The El Niño Southern Oscillation (ENSO) climate-variability phenomenon greatly affects water availability in the Southeast United States. For example, it is well known that La Niña conditions bring drought to this region. In the past decade, several severe droughts have adversely impacted the water resources of many communities in this region, especially those that rely on surface-water systems. Because small- to mid-size communities are most vulnerable to climate variability, this study was undertaken to develop a climate variability–based community water deficit index (CWDI) for use by water managers in these communities. Although currently available drought indices can be useful tools for monitoring and forecasting purposes, they are not suitable for use in water-supply systems for small- to mid-size communities. The CWDI was conceptualized keeping in mind that it should (1) forecast hydrologic drought, (2) operate at a high spatial resolution, and (3) address both water supply and demand during droughts. The system dynamics–modeling software Structured Thinking Experiential Learning Laboratory with Animation was used to develop the modeling framework to estimate CWDI by evaluating differences in a community water supply and demand, and thus help forecast the severity of an impending drought. Another important feature of the CWDI is its ability to evaluate how drought-management policies can affect the severity of drought. The CWDI was tested in two small- to mid-size communities of this region (Auburn, Alabama, and Griffin, Georgia). The results indicate that the index not only can monitor drought in the studied water-supply systems, but can also forecast ENSO-induced hydrologic droughts in the region and can be used in drought planning.