A Watershed Perspective

The dictionary defines a watershed as the area of land, ‘a regional basin,’ that drains rainwater into a common body of water--a creek, bay or ocean. Simply put, a watershed encompasses all the land surface that collects and drains water down to a single exit point. Watersheds can be as large as the Mississippi basin which drains 41% of the lower 48 US states into the Gulf of Mexico. They can also be as small and local as all the “land” of your Rossmoor Entry, including rooftops, yard, and driveway from which water flows to the storm drains and out to Tice Creek. Watersheds at all scales are evolved interdependent webs of living organisms unique to that geographic area based on the soils, atmosphere, climate, and water.

• Five essential functions of a watershed:

1. Rainfall collects and seeps into the ground

2. Water collects in various places (lakes, wetlands, and water tables)

3. Gravity releases water that forms creeks and rivers before entering oceans

4. Watershed areas provide diverse sites of mineralogical reactions for soil building

5. A watershed establishes ecological conditions for biodiverse flora and fauna to flourish

• Managing a healthy watershed for our community

The property boundaries of Rossmoor are nearly contiguous with the upper boundaries of the Tice Creek watershed. While Tice Creek is less than five miles long, its source lies within Rossmoor. We have legal rights to use the water, but we also have a responsibility to conserve and protect its watershed. This includes protecting water quality, supporting its biodiversity, and restoring native habitat to support native wildlife and the natural beauty of the whole ecosystem.

• Tice Creek's tributary connection with Walnut Creek

The Walnut Creek Watershed has 309 miles of creek channels, accounting for almost a quarter of all creek channels in the county. It is 146 square miles (96,000 acres) of mountaintops to marshland–from the protected natural lands of Las Trampas Wilderness and the eastern face of Briones Regional Park to the grazing lands and adjoining neighborhoods of Walnut Creek Open Space in Mt Diablo's foothills to Pacheco Marsh where Walnut Creek empties into Suisun Bay.

• The importance of slowing down the water

From mountaintop to marsh, everything humans do affects the health of our community's watershed. For example, covering land with buildings and parking lots creates impervious areas where water seepage decreases. Most of that runoff drains via culverts which channels the water, accelerating the flow. This fast-moving water then causes erosion as it enters streams. For a healthy watershed, stormwater needs to be slowed and spread across the land, where it will sink in naturally.