Groundwater

Groundwater is the most difficult aspect of Oregon's water to measure. It primarily exists in the spaces between soil and rock particles underground. Groundwater is particularly important in Eastern and Central Oregon, where surface water supplies are limited.



Created by Gareth Baldrica-Franklin, Institute for Water and Watersheds, Oregon State University

















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.

Recharge(mm/yr)

0     20     100     500

Aquifer Type

 Sand/Gravel

 Volcanic

 Other

Hover over map for details

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.


Recharge(mm/yr)

0     20     100     500

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.


Recharge(mm/yr)

0     20     100     500

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.


Recharge(mm/yr)

0     20     100     500

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.

Groundwater Irrigation Rights

Aquifer Type

Sand & Gravel

Volcanic

Other

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.

2010 Total Groundwater
Use in Mgal/day



300+

200 - 300

100 - 200

25 - 100

0 - 25

Hover over counties for details

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.



GW Critical Area

GW Limited Area

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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.

GW Management Area

Hover over areas for details