Percentage of Surface Drinking Water from Intermittent,
Ephemeral, or Headwater Streams in California
Sacramento
San Francisco
Key:
Intermittent, ephemeral and
headwater stream miles as a
percentage of total stream miles
contained in all SPAs for a given
county
~	16% - 42%
~~ 43%-57%
5S% - 69%
70% - 86%
S7% - 100%
~	No Data
Legend: This map highlights regional
patterns of dependence on intermittent,
ephemeral, and headwater streams for surface
drinking water in California. In California,
32,688 total miles of streams provide water
for surface water intakes supplying public
drinking water systems; of this, 18,592 miles,
or 57%, are intermittent, ephemeral, or
headwater streams. Over 7.3 million people in
California 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 4th
Quarter 2006 Data.

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