Office of Columbia River photo identifier

Office of Columbia River

WRIAs 37, 38 & 39
(Lower Yakima, Naches & Upper Yakima)

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

Overview of WRIAs 37, 38 & 39 (Lower Yakima, Naches & Upper Yakima) Results

The regulated tributary surface water supply forecast for the Yakima is characterized by increases from late fall through early spring. Decreases are notable in the late spring and early summer under all flow conditions, continuing through the summer into mid-fall under average and wet flow conditions.

Irrigation is the primary source of demand in these WRIAs. Federal flow targets, shown for Yakima River at Parker for both the historical and the future case, are also important. While small in comparison with irrigation demands, municipal demands are significantly larger than most other WRIAs of eastern Washington. Assuming no change in irrigated acreage, irrigation demand is forecasted to increase in most months in the future, with small variations in the magnitude of this future increase when alternate future economic scenarios are considered. Municipal demand is projected to grow by 23% 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, combined municipal and surface water irrigation demands and federal instream flow targets are projected to outstrip regulated tributary supply at the watershed scale during most years for June through October. Modeling of curtailment of pro-ratable irrigation water rights indicated that it occurred in 45% of years between 1977 and 2005. The resulting unmet demand ranged from 7200 to 278,600 ac-ft per year depending on yearly flow conditions, with an average of 108,000 ac-ft per year. Simulation of future curtailment suggested that it will occur in 90% of years for the middle climate scenario. The resulting unmet demand ranged from 14,300 to 434,000 with an average of 154,000 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 federal flow targets 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.

Yakima summer steelhead stocks are part of the ESA-Threatened Mid-Columbia steelhead listing unit. Juveniles are rearing year-round and outmigrating primarily in April and May. Coho and sockeye are being re-introduced to the Yakima system. Bull trout in the Yakima Basin are part of the Middle Columbia bull trout listing unit.


WRIA 37-39 Supply graphModeled historical (1977-2006) and 2030 surface water supply generated within the WRIA for dry (20th 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

Fish Table WRIA 37-39

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

Management Context

Adjudicated Areas YES (basin-wide adjudication in process)
Watershed Planning Phase 4 (Implementation)
Adopted Instream Flow Rules NO
Fish Listed Under the Endangered Species Act* Middle Columbia River Bull Trout
Middle Columbia Steelhead  
[WRIA 37 is also Columbia mainstem migratory corridor]
Ground Water Management Area NO
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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