Watersheds have been in the public eye more than usual lately.
What’s a “watershed”?
A watershed is an area of land that drains to one place, such as the sea, lake, or another stream or river. Watersheds are bordered by ridges or rises or other raised boundaries that separate them from the neighboring watershed -- water on the other side of the boundary drains another direction. Watersheds can be any size, and larger watersheds have smaller watersheds tightly nested within them. Most watersheds eventually drain to the sea.
The 730-square-mile Coos Watershed drains to empty out through the mouth of the Coos Bay near Charleston; the 1,060-square-mile Coquille Watershed drains to empty out at the mouth of the Coquille River at Bandon. Both watersheds have many smaller watersheds within them.
It seems to me that the size and shape of each drainage and sub-drainage, as well as the steepness of land drained, are functions of the amount and timing of precipitation, the kind of soil and the formations of bedrock, the plants living on the surface, and the length of time the land area was exposed to such erosion.
Rain falling on land doesn’t just flow over the top like a hose pouring water over concrete: at least some rain (or melting snow) percolates into the ground. Gravity pulls groundwater down just as it does surface water; groundwater can flow underground over the top of more pervious rocks or it can gather in underground lakes or fill the tiny holes in porous rock and be stored. (An “aquafer” is an underground body of water.)
The “water table” marks a top boundary of water under the ground: below the water table the ground is saturated, above the water table the ground is not saturated. (“Wetlands” -- and often lakes and ponds, or even streams and rivers -- could be described as a place where the water table is higher than the surface of the ground.)
Underground water, moving or stable, is part of the watershed, too.
Where does the water in a watershed come from? Where does it go?
It recycles, of course. Every school child draws the water cycle: water evaporates from the sea, droplets form clouds, water falls from the clouds onto land, fallen water collects in lakes and rivers, water flows back to the sea.
But there's more to that simplistic view we remember from childhood. This life-sustaining cycle is actually a complex three-dimensional circuit with innumerable branches and off-shoots, one that fully involves all the soil, plants, and animals -- including us.
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That full involvement of all the elements in the watershed, centered on life-sustaining water, is the key to watershed importance. Water flows downstream, carrying sediment and plants and animals; animals use the water to move upstream, too. All the parts of a watershed are connected through the vital, flowing water.
Watersheds are natural parcels for looking at and using the landscape.
To promote healthy, sustainable land-use practices, Oregon has 90 “watershed associations” and “watershed councils” of various sizes, covering nearly every square mile of the state. Watershed associations and councils are non-profit groups that partner with landowners and organizations to conduct and encourage good stewardship.
Watershed associations center on missions that “help protect and restore healthy watersheds and natural habitats that support thriving communities and strong economies.” (Oregon Watershed Enhancement Board Mission Statement.)
Such associations work to enhance stream environments (increasing shade and diversifying water habitats, for example), control noxious weeds (such as gorse), restore wetlands, improve tidegates, monitor fish populations and stream conditions, and more. Watershed associations also look toward the future, including anticipating and planning mitigation for sea level rise. Ideas for such projects come from landowners, staff, and others.
Why have watersheds been in the local news and calendars lately?
The Coos Watershed Association and the Coquille Watershed Association, two of the oldest in the state, are both celebrating their 25th Anniversary this year with gala fundraising events in September.
Watershed stewardship is valuable work that’s well worth celebrating!