DEQ and the Virginia Drought Monitoring Task Force (DMTF) use four hydrologic indicators across thirteen Drought Evaluation Regions to gauge the presence and severity of hydrologic (water supply) drought. The indicators are based on the amount of precipitation and the effect of the precipitation (or lack thereof) on the hydrologic system. Each indicator has thresholds for drought stage determination. 

Groundwater levels are monitored at key shallow water-table observation wells that are part of the Virginia Climate Response Network. Precipitation deficits are monitored by comparing current precipitation amounts with historical precipitation values as a percent of normal long-term values. Streamflow is monitored at real-time stations with a long-term period of record on streams that have moderately large drainage areas and no significant regulation of flow by dams or impoundments. Reservoir storage is monitored at large multi-purpose reservoirs or at water-supply reservoirs. 

The map below depicts Virginia's 13 designated Drought Evaluation Regions and shows the counties and cities encompassed by each Region.  Specific localities located within each Region are identified in the Virginia Drought Assessment and Response Plan.