Climate and Rainfallpicture of rainboots

The Coast Fork Willamette Watershed is situated between the Coast Range (to the west) and the Cascade Range (to the east). The Willamette Valley is on the leeward side of the Coast Range, and therefore receives less moisture and precipitation than the windward side of the range. However, because the Coast Range is not very high elevation (approximately 1,400 feet average), a significant amount of moisture is able to travel eastward in an air mass across the range without losing all of its’ moisture. Once the humid air hits the Cascade Range, orographic uplift of an air mass is more significant.

Watershed members living in two distinct locations in the watershed, Silk Creek and Dorena Lake, collect rainfall data which we track online.

More information about the local climate and weather can be found at the Cottage Grove Chamber of Commerce site.


Stream Flow

The fourth-field Hydrologic Unit Code (HUC) for the Coast Fork Willamette Watershed is 17090002. There are eight historic USGS gauge sites within the watershed, five of which are active. Real-time data about river flow levels are available in several formats and historical data is searchable. These are linked below:

USGS 14152500 Coast Fork Willamette at London, OR
USGS 14153500 Coast Fork Willamette River below Cottage Grove Dam, OR
USGS 14154500 Row River above Pitcher Creek, near Dorena, OR
USGS 14155500 Row River near Cottage Grove, OR
USGS 14156000 Mosby Creek near Cottage Grove, OR
USGS 14156500 Mosby Creek at mouth, near Cottage Grove, OR
USGS 14157000 Coast Fork Willamette River at Saginaw, OR
USGS 14157500 Coast Fork Willamette River near Goshen, OR
USGS Current Conditions for Oregon–230 Sites


Water Rights and Uses

Water rights in Oregon are governed by the prior appropriation doctrine, which gives the oldest rights priority over newer or ‘junior’ rights. Another overarching component of the law is the ‘use it or lose it’ approach in which rights must be documented as in use consistently within the last five years or they could be revoked under the law. A good method of maintaining an unused water right would be to transfer the irrigation rights into the stream for 1-5 years—see the Water Resources Department Instream Leasing Program for more information.

Water rights are attached to a property, not the property owner, and transfers usually must occur within the tributary they are allocated to—it may be possible to move a right further downstream from its existing location, but the opposite could be quite difficult. A water right is needed to use, store, or divert water for a beneficial use. However, exempt uses include domestic use (up to 15,000 gal/day), commercial use (up to 5,000 gal/day), and irrigation of ½ ac lawn and garden. New wells must be approved and permitted, but these exemptions exist for existing wells and legal surface water supplies.

For more information about water rights, visit these websites:


KEEP IN TOUCH: Join our newsletter to receive updates and event notifications.