Percentage of Surface Drinking Water from Intermittent,
Ephemeral, and Headwater Streams in Virginia
Key:
Intermittent, ephemeral, and
headwater stream miles as
percentage of total stream
miles contained in all SPAs
for a given county
Legend: This map highlights regional patterns of dependence on intermittent, ephemeral, and headwater streams for surface drinking water in Virginia. In Virginia, 9,260 total miles of
streams provide water for surface water intakes supplying public drinking water systems; of this, 5,290 miles, or 57%, are intermittent, ephemeral, or headwater streams. Over 2.3 million
people in Virginia receive drinking water from public drinking water systems that rely at least in part on intermittent, ephemeral, or headwater streams. This analysis compared the stream
length of intermittent, ephemeral, and headwater streams to total stream length within all mapped Source Protection Areas (SPAs) for each county. A SPA is an area upstream from a drinking
water source or intake that contributes surface water flow to the drinking water intake during a 24-hour period. This is based on data that generally do not include streams less than one mile in
length. Intermittent streams are streams containing water for only part of the year. Ephemeral streams flow in response to precipitation events. First-order streams have been used to
represent headwater streams.
Data Sources: National Hydrography Dataset Plus at medium resolution; Federal Safe Drinking Water Information System 4thQuarter 2006 Data.

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