Oklahoma Water Resources Board the Water Agency

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Water Facts


Oklahoma is underlain by 22 major groundwater basins containing approximately 390 million acre-feet of water in storage, though only one-half of that amount may be recoverable. Groundwater is the prevalent source of water in the western half of the state.

The state's largest groundwater basin, the Ogallala Aquifer in western Oklahoma, contains 90 million acre-feet of supply--enough to cover the entire state two feet deep.

Surface Water

Oklahoma contains approximately 1,401 square miles of water area in its lakes and ponds (larger than the state of Rhode Island).*

Oklahoma has approximately 167,600 miles of rivers/streams.*

Oklahoma's longest river is the Beaver/North Canadian River (752 miles); the Red River is the second longest (570 miles).*

Oklahoma's largest lake in surface area is Eufaula (105,000 acres); Lake Texoma is second (88,000 acres). The state's largest lake in conservation storage is Texoma (2.6 million acre-feet of water); Eufaula is second (2.3 million acre-feet).

Average annual lake evaporation in Oklahoma ranges from 48 inches in the extreme east to 65 inches in the southwest, numbers that far exceed the average yearly rainfall in those areas.

*based on USGS 1:24,000 scale

Water Use

According to data compiled for the 2012 Update of the Oklahoma Comprehensive Water Plan, total water use in Oklahoma in 2007 was 1,814,762 acre-feet:

  • Approximately 56% of this use came from surface water sources and 44% from groundwater sources;
  • Approximately 73% of this water was used for Crop Irrigation and Municipal/Industrial combined, Oklahoma's two largest water use sectors.

Crop irrigation (41% of total use) is the number one use of water in Oklahoma; public water supply (32%) is second, followed distantly by livestock and aquaculture (12%).

Groundwater accounts for 73 percent of total irrigation water use in Oklahoma.

The majority of the state's surface water (approximately 54 percent) is used for public water supply.

The approximate number of stream water permits on file at the OWRB is 2,600; the approximate total allocated stream water use in Oklahoma is 2.6 million ac-ft/year.

The approximate number of groundwater permits on file at the OWRB is 10,000; the approximate total allocated groundwater use in Oklahoma is 3.2 million ac-ft/year.

Evaporation and percolation preclude immediate use of approximately 80 percent of Oklahoma stream water.

Each year, approximately 10.5 million acre-feet of water flows into Oklahoma through its two major river basins, the Red and Arkansas. An average of almost 36 million acre-feet flows out of the state each year.


Almost half of flood-related deaths occur in vehicles, primarily when people drive into flooded highway dips or low-drainage areas at night.

There are approximately 40,000 structures in Oklahoma that reside within the boundaries of the regulatory floodplain, yet less than 10,000 of these are covered by flood insurance.

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Last updated: December 11, 2020

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