Rain-dependent streams (ephemeral) flow only after precipitation. Larger seasonal streams are more common in dry areas. During dry periods, seasonal streams may not have flowing surface water. Runoff from rainfall or other precipitation supplements the flow of seasonal stream. Seasonal streams (intermittent) flow during certain times of the year when smaller upstream waters are flowing and when groundwater provides enough water for stream flow. Most of the water comes from smaller upstream waters or groundwater while runoff from rainfall or other precipitation is supplemental.Ĭlick on the map above to see the percentage of people in your county that gets some of their drinking water directly or indirectly from streams that are seasonal, rain-dependent or headwaters. Year-round streams (perennial) typically have water flowing in them year-round. Flow in a headwater may be year-round, seasonal, or rain-dependent. The very foundation of our nation’s great rivers is a vast network of unknown, unnamed and underappreciated streams. Almost 60 percent of stream miles in the continental U.S only flow seasonally or after storms. About 53 percent of the total stream miles in the continental U.S. Headwater streams and streams that only flow for part of the year make up the majority of river miles in the United States. Yet other headwaters originate in marshy meadows filled with sluggish tea-colored water. Other spring-fed headwaters contain clear water with steady temperature and flow. Desert headwater streams can arise from a spring and run above ground only a few hundred yards before disappearing into the sand. Headwaters can be streams that flow briefly when snow melts or after rain, but shrink in dry times to become individual pools filled with water. Headwater streams are the smallest parts of river and stream networks, but make up the majority of river miles in the United States.

Because small streams and streams that flow for only part of the year are the source of the nation’s fresh waters, changes that harm these headwaters affect streams, lakes and rivers downstream. Headwater streams trap floodwaters, recharge groundwater supplies, remove pollution, provide fish and wildlife habitat, and sustain the health of downstream rivers, lakes and bays. Headwater streams are the beginnings of rivers, the uppermost streams in the river network furthest from the river's endpoint or confluence with another stream. Like the photos on this page? Visit our Flickr Gallery to see more streams. These small streams often appear insignificant, but in fact are very important, as they feed into and create our big rivers.On this page: These water sources, which scientists refer to as headwater streams, are often unnamed and rarely appear on maps.Yet the health of small streams is critical to the health of the entire river network and downstream communities. They could be a drizzle of snowmelt that runs down a mountainside crease, a small spring-fed pond, or a depression in the ground that fills with water after every rain and overflows into the creek below. Comparisons between forested and urban watersheds also highlight the difficulty of identifying headwater channels using topographic attributes in human-modified landscapes.Small streams, including those that don’t flow all of the time, make up the majority of the country’s waters. Small ephemeral channels with less defined banks or originating at groundwater seeps were difficult to detect in all methods. The TO-based networks detected a larger number of ephemeral channels, but with higher commission error.

Although the NHD and flow accumulation methods resulted in low commission errors, omission errors were highest in these networks. Geological Survey National Hydrography Dataset (NHD) and a flow accumulation approach where a single drainage area threshold defined channel initiation. Predicted networks were compared against a comprehensive field survey of the ephemeral network in each watershed to evaluate performance. A method was developed using topographic openness (TO) and wetness index to remotely predict the extent of stream networks. In this study, elevation data derived from light detection and ranging was used to predict ephemeral stream networks across a forested and urban watershed in the Maryland Piedmont USA. Increased availability of high-resolution (<2 m) elevation data makes the delineation of headwater channels more attainable.

Under-representations of headwater channels in digital stream networks can result in uncertainty in the magnitude of headwater habitat loss, stream burial, and watershed function.

Ephemeral stream