Aquifers and Recharge

Groundwater exists in aquifers, which vary based on rock type. Oregon has three principal aquifer rock types. Different aquifer types have variable productivity and accessibility.

Groundwater recharge is a measurement of how quickly aquifers are replenished with new water. Recharge mainly depends on precipitation, elevation, permeability and plant cover. Greater recharge generally means more sustainable groundwater.

Sand and Gravel

Sand and gravel

aquifers exist in lowlands and river valleys. They are shallow, accesible, and comprise the most productive aquifers in the state.

Sand and gravel aquifers are formed by erosion or faulting. They typically yield 20-2,000 gallons per minute to wells.

Volcanic

Volcanic

aquifers cover Eastern and Central Oregon. Basalt flows form the most productive volcanic aquifers, while other volcanic formations are more variable.

Many volcanic aquifers exist in remote areas. As a result, there is a lack of information about the depth of these aquifers.

Other

Other

aquifers in Oregon consist of various rock types. Many of these rock types are older than previously discussed aquifers, and they typically have marine origin.

These aquifers, on average, yield 1 to 100 gallons a minute to wells, making them among the least productive aquifers in the state.

Irrigation and Aquifers

Almost 90% of Oregon's groundwater extraction is used for irrigation. Each point on the map represents a claimed irrigation water right, and is colored based on the underlying aquifer type.

With so much reliance on specific aquifers, especially in the drought-prone regions of Eastern Oregon, groundwater sustainability becomes paramount.

County Groundwater Use

The USGS National Water Use Information Program compiles water use data by county every five years. Water use data is categorized by both its purpose (irrigation, domestic, mining, etc.) and its type (surface or ground, fresh or saline). Data are collected in terms of millions of gallons extracted per day.

Groundwater Conservation

Critical Groundwater Areas

are created in areas where it is estimated that extraction has resulted in declining groundwater levels. Critical groundwater areas face restrictions on withdrawal rates and limits on the ability to obtain new groundwater permits. The program began in 1965.

The

Groundwater Limited Area

program is designed to conserve groundwater in areas where groundwater levels are at risk of falling. Restrictions in groundwater limited areas are often not as severe as they are in critical groundwater areas.

Groundwater Management

Groundwater Management Areas (GWMA) are declared by the Oregon Department of Environmental Quality in areas that have increased contaminant levels. The three designated GWMAs in Oregon were all created in response to increased nitrate levels. Local management committees in affected areas work with state agencies to produce action plans for reducing contaminant levels.