Percentage of Surface Drinking Water from Intermittent,
Ephemeral, or Headwater Streams in Iowa
Intermittent, ephemeral, and
headwater stream miles as
percentage of total stream
miles contained in all SPAs
for a given county
50% - 56%
57% - 69%
Mason City
70% - 86%
87% - 98%
No Data
JCedar Falls
Sioux City
Cedar Rapids
Iowa City
Des Moines
Council Bluffs

Legend: This map highlights regional patterns of dependence on intermittent, ephemeral, and headwater streams for surface drinking water in Iowa. In Iowa, 3,811 total miles
of streams provide water for surface water intakes supplying public drinking water systems; of this, 2,319 miles, or 61%, are intermittent, ephemeral, or headwater streams.
Over 660,000 people in Iowa 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.