What is a Watershed

One simple definition is that a watershed is the land that water flows across or under on its way to a stream, river, lake or larger body of water (such as an ocean). Water always seeks the lowest point. It may travel over the surface or seep into the soil and travel as ground water. Often called a drainage basin, a large watershed like that of the Clark Fork-Pend Oreille can consist of many smaller watersheds or sub-basins across several states. The Clark Fork-Pend Oreille watershed covers 26,000 square miles in Washington, Idaho and Montana. Everyone lives in a watershed and is part of a watershed community.

Most watersheds are composed of a mixture of landscape types, including wetlands, uplands, riparian areas, streams and lakes. The rain and snow that falls onto a watershed which doesn't evaporate is stored in the soil. Over a period of time that water is released through groundwater, wetlands and streams. This water continues to flow down-slope and eventually reaches the mouth of the river that drains the watershed. Uplands are areas where standing water is usually not found due to its slope or permeability. A riparian area is a zone of transition between an upland and a river, lake or stream. Riparian plants protect stream banks from erosion during floods and runoff periods. Riparian forest soils filter out sediments, pollutants and debris from streams, lakes or other water bodies.The water gradually leaks out, replenishing streams and lakes during dry summer months.

A wetland is a low-lying area that is wet during extended periods of the year. Bogs, swamps, ponds and marshes are types of wetlands. Vegetation and wetlands are present in a healthy watershed to intercept and slow the flow of water as it travels through the watershed, removing sediment and allowing large quantities of water to enter the soil and percolate into the groundwater--or aquifer. Most of our drinking water comes from an aquifer. Many people live right over their aquifer. The Missoula Valley Aquifer, for example, is no more than 30 feet below the valley floor. The water table is just below the surface where the Clark Fork and Bitterroot join. Contaminants reaching surface water may eventually find their way into our drinking water.

Most human activities and development have the potential to harm the overall health of a watershed. Timber harvesting on unstable slopes without proper precautions can cause erosion. Agricultural activities can increase levels of harmful bacteria and overload runoff with nutrients. Poorly planned urban and industrial growth can cause erosion, stormwater runoff problems and contamination from toxic chemicals. Even rural development and recreational activities can be harmful when they destroy the watershed's sensitive riparian vegetation. All of the natural resources in a watershed are influenced by what happens in it, such as erosion, effluent or change in flow. Natural resources downstream are also affected by whatever goes on in the watershed upstream. Pollutants introduced to the watershed near Butte may end up in Pend Oreille Lake!

The effects of numerous activities within a watershed are cumulative. Managing land area according to watershed boundaries, rather than the arbitrary boundaries of a county, state or city, makes sense bacause the natural boundary defined by a watershed is self-contained. Cumulative effects can be better addressed from this perspective. (See the Watershed Boundary Map.)

Remember, we all live downstream from someone!

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NUTRIENT FACT SHEET

Nutrients occur naturally in our environment as a source of energy for living organisms. In every aquatic ecosystem, nutrients are natural components that act as stimulants for plant growth. The fertility of a stream is an important factor in fish production and the ability of aquatic life to live and thrive.

However, when a water body becomes overloaded with nutrients, such as nitrates and phosphates from natural or cultural sources, excessive growths of algae may result. Large concentrations of algae can deplete the oxygen needed by fish and other aquatic organisms to survive, make the water body less appealing for recreational use, clog irrigation flows, and impact drinking water supplies.

Many human activities in a watershed can increase the amount of nutrients that enter our streams, lakes and rivers. Nutrients found in stormwater runoff from streets and parking lots, lawn and garden fertilizers, and septic system drain fields can drain or leach into nearby water bodies, causing more algae and aquatic weeds to grow. Soil particles carry nutrients with them, too, so earth-moving activities such as construction, road building, and farming can contribute nutrients to a water body. When soil particles settle to the bottom of a stream, lake or river, they can also fill in the water body and damage fragile fish habitat.

A delicate balance exists between our rivers, lakes and streams and the surrounding watershed. Most of us aren’t even aware of how the things we do can affect our water quality. The following list offers practical tips to help you protect the Clark-Fork Pend Oreille watershed: