A watershed is defined by high points of land, when rain falls within a watershed it flows overland or underground towards a local stream, like Yorkson Creek. The Yorkson Creek watershed is defined by higher points of land that separate it from the Salmon and Nicomekl River watersheds

In a natural watershed system most rain water percolates into the ground and is slowly released into the stream as clean groundwater.

In a developed area, like the community of Walnut Grove, the ground is covered with impervious surfaces like roads, roof tops, driveways, and parking lots. In a developed area most rain water flows overland to storm drains which carry the water through a system of pipes directly to the stream. As the rain water flows over land it picks up pollution like fertilizers, weed killers, dog waste, oil, and antifreeze which are then carried directly to the stream. This pollution has many negative impacts on fish, amphibians, aquatic insects, water birds, and other wildlife that depend on clean water.

As a resident of the Yorkson Creek watershed, YOU impact Yorkson Creek regardless of how close you are to the creek.

Watershed Urbanization

Urbanization (or development) has a large impact on local water systems. It changes how water flows in the watershed and what flows in the water. Both surface and groundwater are changed.

As a watershed becomes developed, trees, shrubs and other plants are replaced with impervious surfaces (roads, rooftops, parking lots and other hard surfaces that do not allow stormwater to soak into the ground). Without the plants to store and slow the flow of stormwater, the rate of stormwater runoff is increased. Less stormwater is able to soak into the ground because sidewalks, roads, parking lots and rooftops block this infiltration. This means a greater volume of water reaches the waterway faster and less of that water is able to infiltrate the ground. The reduced amount of infiltrating water can lower ground water levels, which in turn decreases the baseflow levels in our creeks.

In the stream, erosion of stream banks and scouring of channels can potentially occur due to decreased frequency and volume of runoff. This degrades habitat for plant and animal life that depend on clear water. Sediment from eroded stream banks clogs the gills of fish and blocks light needed for plants. The sediment settles to fill in stream channels, lakes and reservoirs. This also increases flooding and the need for dredging to clear streams or lakes for boating.

In addition to the high flows caused by urbanization, the increased runoff also contains increased contaminants. These include litter, cigarette butts and other debris from sidewalks and streets, motor oil poured into storm sewers, heavy metals from brake linings, settled air pollutants from car exhaust and pesticides and fertilizers from lawn care. These contaminants reach local waterways quickly after a storm.

Human Impact

Pollution caused by humans is one of the biggest threats to Yorkson Creek. There are two types of pollution, point and non-point source pollution. Point source pollution is "end of the pipe" pollution that can be identified as coming from a specific source such as a factory, industrial plant or some other facility. In the past, most environmental laws dealt with this particular form of pollution, however the most serious threat to our water quality is from non-point source pollution.

Non-point source pollution are pollutants that are carried off the land by stormwater into Yorkson Creek. The water picks up pollutants left by human actions such as: