Water Quality Monitoring and Subbasin Characteristics

Monitoring

DEQ regularly samples four sites in the Yamhill Subbasin (on the South Yamhill, North Yamhill and Yamhill Rivers and on Salt Creek) and measures stream health indicators like nutrients, bacteria, dissolved oxygen, temperature and pH (a measure of acidity). DEQ measured these indicators, as well as periods of hourly temperature and hourly dissolved oxygen, at several additional locations between 2005 and 2009. DEQ can also use stream measurements collected since 2002 by the Yamhill Basin Council for water quality analysis because those data meet DEQ data quality standards. DEQ and watershed council data are available on DEQ’s online database (LASAR).

To find Yamhill Subbasin environmental data in LASAR, follow these instructions:

1. Go to the LASAR Database
2. Select “Geography”
3. In the "Subbasin" box scroll down and select “Yamhill”
4. Select the “View/Select Stations” box
5. Check the box beside one (or more) stations
6. Select the “Get sample results” box at top of the page
   

Subbasin Characteristics

The Yamhill Subbasin is a watershed. A watershed is a drainage area in which all the precipitation that falls as rain or snow and isn’t evaporated or transpired by vegetation, ultimately drains to one waterway, in this case the Yamhill River.

The following is a list of characteristics of the Yamhill Subbasin:

• The Yamhill Subbasin comprises approximately 770 square miles.
  • Yamhill Subbasin in the Willamette Valley PDF
• The South Yamhill River flows eastward about 62 miles from the Coast Range to join the North Yamhill River. The combined volume of the North and South Yamhill Rivers flows an additional 11 miles as the Yamhill River before entering the Willamette River at approximately river mile 55.
• Land ownership in the Yamhill Subbasin is 87% private, 12% federally owned, and 1% state owned.
  • Yamhill Subbasin Land Ownership PDF
• Land use is 56% agriculture, 38% forestry, 4% rural residential and 2% percent urban.
  • Yamhill Subbasin Land Cover PDF

Watershed Assessments for the Yamhill Subbasin are available on the Yamhill Basin Council Website.