Streams and Waterbodies in California The National Hydrography Dataset This map displays the pattern of different surface water feature types across the state of California, 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 415,764 miles of linear streams in California, 79 percent (330,312 miles) are intermittent or ephemeral. Eight percent of streams are ditches (34,189 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. &eDBr*>* /=. 'J USGS (j&) IS science for a changing world Prepared by INDUS Corporation under contract with U.S. Environmental Protection Agency Office of Water — Washington, DC Ocotober 2013 SURFACE WATER FEATURES ¦ STREAM/RIVER - PERENNIAL ~ STREAM/RIVER - INTERMITTENT ~ STREAM/RIVER - EPHEMERAL ~ STREAM/RIVER - UNCLASSIFIED O CANAL/DITCH O LAKE/POND OR RESERVOIR ¦ SWAMP/MARSH ~PLAYA ~ WASH EZI STATE BOUNDARY 0 100 200 400 Miles 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. ------- |