Rivers

Rivers are the primary driver of surface water systems. The largest river in Oregon is the Columbia, which snakes its way across the northern Oregon border. Many of Oregon's larger rivers are tributaries of the Columbia, such as the Willamette, Deschutes, and John Day. Other major rivers include the Klamath, Rogue, and Umpqua.

Widespread damming has reduced the flow of many Oregon Rivers below their natural levels. The John Day River is the longest river in Oregon that has remained undammed.

Watersheds

Rivers define watersheds (or basins). Watersheds represent the total area that drains into a river, or river section. Watersheds can be defined at various scales, representing vast basins of major rivers, or small areas of urban creeks.

Mid-level watersheds are shown on the map, and are colored by their underlying basin.

Lakes

Oregon has many lakes. Some are naturally occurring, some are manmade, and some are ephemeral, only existing in wet months. Many of Oregon's largest naturally occurring lakes exist in the southern part of the state.

Watershed Councils

Watershed councils are independent, voluntary organizations established to improve watersheds in their localities. Watersheds are strictly managed locally, although the state provides guidance for their formation. Councils assess local water conditions, provide restorative and conservation services, and create communities centered around protecting water.

Major Wetlands

Over 40% of Oregon's wetlands have been drained or filled-in since Euro-American settlement. Wetlands are among the most important ecosystems for wildlife and water quality. Wetlands store and clean water, prevent erosion, and control flooding. They are also important habitats for a variety of plants and animals.

This map shows Oregon's "Greatest Wetlands", which were identified by the Wetlands Conservancy.

Pollution

The Oregon Department of Environmental Quality (DEQ) assesses rivers and lakes for pollutants. Pollutants can include minerals, chemicals, biological agents, or sediments. Temperature issues are also classified as pollutants. If identified pollutants are above certain concentrations, a waterbody is declared Water Quality Limited for that pollutant.

The map aggregates all identified water quality limited pollutants for 2012 into their respective watersheds.