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Office of Columbia River

WRIA 49 (Okanogan)

  • Overview
  • Supply
  • Demand
  • Supply & Demand
  • Instream
  • Management Context
  • Water Allocation

Overview of WRIA 49 (Okanogan) Results

The tributary surface water supply forecast for Okanogan is characterized mostly by increases from mid-fall through winter and decreases under most flow conditions from late spring through early fall.

The largest demands in WRIA 49 are from instream demands, though irrigation demands are also important. Municipal demands are much smaller. Because the instream flows specified in Chapter 173-549 WAC are higher for some time periods for the middle Okanogan River near Tonaskett than for lower Okanogan River at Malott, instream requirements are shown as the higher of these two instream flow requirements for each month, for both the historical and future period. Assuming no change in irrigated acreage, irrigation demand is projected to increase in most months but decrease in others under all future economic scenarios that were considered. Municipal demands are forecasted to grow by 22% by 2030.

If provided, additional water capacity as specified by the proposed projects in the Office of Columbia River "medium" scenario is anticipated to increase agricultural irrigation water demand in this WRIA compared to 2030 irrigation water demand under the economic base case (a scenario of no additional capacity). Additional capacity will increase demand in all WRIAs where water is provided for new irrigated land.

In 2030, at the watershed scale, combined municipal and surface water irrigation demands and adopted instream flows are projected to outstrip unregulated tributary supply generated within the Washington portion of the watershed during most years for May through February. Upstream portions of the watershed outside of Washington provide additional supplies, but may also have additional demands. Additional water supplies from the Columbia River are available to meet demands in a few areas of the WRIA, and a separate analysis indicates that roughly one sixth of agricultural demand is within a mile of the Columbia River (results shown in "Washington's Columbia River Mainstem: Tier III Results"). Modeling of curtailment of interruptible irrigation water rights indicated that it occurred in every year between 1977 and 2006. The resulting unmet demand ranged from 144 to 11,388 ac-ft per year depending on yearly flow conditions, with an average of 4,426 ac-ft per year. Simulation of future curtailment occurred in 97% of years for the middle climate scenario. The resulting unmet demand per year ranged from 263 to 21,292 with an average of 10,464 ac-ft per year. Due to data and resource constraints, the modeling of unmet demand did not consider curtailment of one water user in favor of another more senior water right holder. Although not shown here, unmet demands due to a failure to meet adopted instream flows are shown in the technical report. Water shortages outside the scope of this analysis may also exist in localized areas, and over time periods within months.

The Okanogan summer steelhead stock is a component of the ESA-Threatened Upper Columbia steelhead listing unit. These fish spawn from March through June, juveniles over winter, and juvenile outmigration generally occurs in April and May. Okanogan sockeye are returning to, rearing in, and migrating from lakes along the U.S. Canada border and in British Columbia.


WRIA 49 Supply graph
Modeled historical (1977-2006) and 2030 surface water supply generated within the WRIA for dry (20
th percentile, top), average (middle), and wet (80th percentile, bottom) flow conditions. The spread of 2030 flow conditions is due to the range of climate change scenarios considered. Supply includes current major reservoir operations for Yakima (WRIAs 37, 38, and 39); otherwise it is the unregulated supply, without consideration for reservoirs. Supplies are reported prior to accounting for demands, and thus should not be compared to observed flows.

Surface water supplies include only supplies generated on tributaries within the Washington portion of the watershed. They do not include water supplies that enter the WRIA from upstream portions of the watershed, nor do they include water supplies from the Snake River or Columbia River Mainstem. These water supplies are characterized in "Tier II: Supply" and "Washington's Columbia River Mainstem: Tier III results."


Historical water demand

Modeled historical (1977-2006) and 2030 irrigation water, municipal, and instream flow demands under average flow conditions, and under the middle climate change scenario considered. Forecast 2030 water demands are shown for three economic scenarios: low, medium, and high growth in the domestic economy and international trade. Ground water (GW, brown) and surface water (SW, dark green) irrigation demands are shown at the “top of crop” and include water that will actually be used by plants, as well as on-field losses based on irrigation type. Conveyance losses (light green) are estimated separately. Consumptive municipal demands (yellow) include self-supplied domestic use, but exclude self-supplied industrial use. Instream flows (blue) for both the historical and 2030 forecast are shown using adopted state instream flows or federal flow targets. When more than one instream flow exists at the sub-watershed level for a given month, the largest value (generally also the most downstream) was used to express instream flows at the WRIA level.

Future water demand

2030 forecasted water demands under the 2030 forecast economic base case (medium economic scenario, no additional water capacity, same as "2030 Medium" in the graph above), and under the 2030 medium water capacity scenario (with the addition of 200,000 ac-ft per year of proposed additional capacity). The medium water capacity scenario examined a specific set of water capacity projects across eastern Washington, and assumed that new surface water supplies would be used for two purposes: as replacement water for acreage in Odessa currently irrigated with groundwater, and to grow crops on land that is not currently irrigated. Irrigation water demand is shown under average flow conditions and for the middle climate change scenario considered. It includes groundwater and surface water demands, as well as conveyance losses, as above.

Supply & Demand

Supply & demand

Comparison of surface water supply, surface water irrigation demands, and municipal demand for 2030, using the baseline economic scenario, and the middle value of the range of climate change scenarios considered. Wet (80th percentile), average, and dry (20th percentile) flow conditions are shown for supply. The 80th, 50th, and 20th percentile conditions are also shown for irrigation demand using error bars. Demands and supplies are defined as above. Water curtailment is not considered.

Fish Status & Utilization by Species

WRIA 49 Fish Table

Fish use of WRIA waters (provided by Washington Department of Fish and Wildlife).

Management Context

Adjudicated Areas Similkameen River 
Sinlahekin Creek 
Whitestone Lake 
Bonaparte Creek & Lake
Lower Antoine Creek 
Johnson Creek 
Duck Lake Groundwater Subarea 
Chiliwist Creek Salmon Creek, Lr & WF & tributaries 
Omak Creek (incomplete)
Watershed Planning Phase 4 (Implementation)
Adopted Instream Flow Rules YES (Chapter 173-549 WAC)
(interruptible users curtailed annually)
Fish Listed Under the Endangered Species Act* Okanogan River Sockeye
Upper Columbia Steelhead
[Columbia mainstem migratory corridor]
Ground Water Management Area YES (Duck Lake subarea)
Ground Water Studies YES (references listed in WSU technical report)


*All species that spawn or rear in WRIA waters are identified. Species that migrate through WRIA waters are not individually identified, but migratory corridors for listed fish species that spawn and rear upstream are noted.

Water Allocation

Water Allocation graph

To give an indication of the amount of uncertainty related to water claims, permits, and certificate data, total annual quantities of water identified under state level water claims, permits, and certificates in Ecology's Water Rights Tracking System (WRTS) are provided, as well as information on the percentage of documents without information. Water documents that could be identified as exclusively non-consumptive uses (e.g. power, fish propagation) were removed from analysis. WRTS data does not include tribal or federal quantified or unquantified water rights.


Definitions used in this Forecast

Basin-Wide Results Tier 1 WRIA Results Overview Tier 2 Mainstem Results Tier 3 WDFW Instream Results


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