Streams and Waterbodies in Idaho

The National Hydrography Dataset

SURFACE WATER FEATURES

¦	STREAM/RIVER - PERENNIAL

~	STREAM/RIVER - INTERMITTENT

~	STREAM/RIVER - EPHEMERAL

~	STREAM/RIVER - UNCLASSIFIED

~	CANAL/DITCH

g LAKE/POND OR RESERVOIR

~	SWAMP/MARSH
~PLAYA

¦	WASH

E2 STATE BOUNDARY

This map displays the pattern of different surface water feature types across the
state of Idaho, including perennial, intermittent and ephemeral streams. Perennial
streams generally contain water throughout the year, except for periods of
extreme drought. Intermittent streams contain water for only part of the year,
while ephemeral streams flow only in response to precipitation events. Although
the intermittent and ephemeral stream classifications are distinguished from each
other in the dataset, many ephemeral streams are included in the "intermittent"
category. In addition, some ephemeral streams in the Southwest have been
classified as washes. Only recently, and mainly on U.S. Forest Service land, have
streams been added to the dataset under the "ephemeral" category, so very few
streams are indicated as such. The map highlights the predominance of
intermittent and ephemeral streams across the state. Of the 170,887 miles of linear
streams in Idaho, 61 percent (103,825 miles) are intermittent or ephemeral. Seven
percent of streams are ditches (12,035 miles), which are not classified by their
flow duration in the dataset.

The water features on the map are from the National Hydrography Dataset (NHD)
at high resolution (1:24,000 scale or higher) (data current as of October 2009).
Many smaller waters are not included in the NHD because they could not be
detected on the original aerial photos used to create the dataset or were excluded
from the maps from which the dataset originates. The majority of perennial and
most intermittent streams are captured at this resolution. However, most
ephemeral streams are not captured unless they are in the arid west. Additional
information on the NHD can be obtained from the NHD website at
https://nhd.usgs.gov.

HUSGS (sb)

science for a changing world

Prepared by INDUS Corporation under contract with
U.S. Environmental Protection Agency
Office of Water - Washington, DC
October 2013

This map relies exclusively on USGS data for mapping water resources such as streams and other waterbodies. Due to the resolution of the map, it does
not distinguish effectively between land and water and thus makes waters appear more prevalent than is actual. This map does not depict the scope of
waters protected under the Clean Water Act or the scope of waters that would be protected under the Army/EPA proposed rule. This map has not been
used for any regulatory purpose.

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