Percentage of Surface Drinking Water from Intermittent, Ephemeral, and
Headwater Streams in Louisiana
Shreveport
Legend: This map highlights regional patterns of dependence on intermittent,
ephemeral, and headwater streams for surface drinking water in Louisiana. In
Louisiana, 4,405 total miles of streams provide water for surface water intakes
supplying public drinking water systems; of this, 1,163 miles, or 26%, are intermittent,
ephemeral, or headwater streams. Over 1.8 million people in Louisiana 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.
Key:
Intermittent, ephemeral, and
headwater stream miles as
percentage of total stream
miles contained in all SPAs
for a given county
1% - 44%
45% - 56%
57% - 69%
70% - 86%
100%
No Data
0	20	40
11^ i
%,	c<°

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