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Office of Columbia River

Columbia River Basin: Tier I Results

  • Tier I
  • Supply
  • Seasonal Availability
  • Survey
  • Agricultural
  • Municipal
  • Instream
  • Hydropower

Columbia River Basin: Tier I Results


Columbia River BasinTier I, the Columbia River Basin, focused on a broad assessment of the basin as a whole, with in-depth analysis of the Washington portion of the basin. To accurately forecast Washington's water supply and demand, it is necessary to understand water supply and demand throughout the entire Columbia River Basin. The major water contributors are British Columbia, Washington, Idaho, Montana and Oregon, while Wyoming, Utah and Nevada are minor contributors by area (see figure at left). The amount and timing of water entering Washington state within the Columbia River Basin is highly impacted by existing infrastructure and management in British Columbia, Idaho, Montana, and Oregon.

Throughout this report, WSU modeling results are presented using specific definitions of supply and demand, described on this page.







Modeled Water Supplies Entering Washington

Modeling results indicated a number of important changes in surface water supply entering Washington between the historical period (1977-2006) and 2030. These changes reflect the impacts of climate change (see figures 1 & 2 below):

• Annual water supplies for most of the eastern incoming rivers, including the Columbia, Pend Oreille, Spokane, Clearwater, Snake, and John Day will increase by 2030, an average of 3.7 (±1.3)%.*

• The direction of change for annual water supplies entering Washington is unclear, 1.4 (±1.9)% on average, for the Similkameen and Kettle Rivers.

• Within a season, surface water supplies entering Washington will generally increase by 2030 in late fall, winter and spring, and decrease in the summer and early fall. This pattern applies to both eastern and western portions of the basin, and is evident at most points where significant amounts of water enter Washington, including the Columbia River and the Snake River. The exact timing may vary somewhat by river.

Surface flows into Washington State

Figure 1. Surface water flows for major tributaries upstream of the point where the rivers enter Washington State. Top number (bold) refers to 2030 forecasted water supplies for average (50th percentile) flow conditions and the middle climate change scenario, while the bottom number (italic) refers to historical (1977-2006) water supplies. All values are in cubic feet per second.


Historical and future regulated surface water supplies

Figure 2. Historical (1977-2006) and 2030 forecasted regulated surface water supplies on the Snake and Columbia Rivers upstream of the point where they enter Washington State 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.

* When discussing modeled supply and irrigation demand results, "average flow conditions" refers to the 50th percentile (middle) value under the middle climate scenario. "Average" by itself refers to the average value over all climate scenarios and flow conditions, and a 90% confidence interval around that average. (back)

Columbia River Basin Surface Water Supply and Seasonal Availability

The forecast of surface water supply and timing in 2030 for all areas of the Columbia River Basin upstream of the Bonneville Dam noted the following changes compared to the historical flows (1977-2006) (see figure below):

• A small increase of around 3.0 (+/-1.2)% in annual supplies.

• Timing changes will shift water away from the times when demands are highest. Unregulated surface water supply at Bonneville will decrease an average of 14.3 (±1.2)% between June and October, and increase an average of (17.5 (±1.9)% between November and May.

Comparison of water supply and demand

Comparison of regulated surface water supply and irrigation water demands for the historical (top) and 2030 forecast (bottom) periods under the medium-growth, medium-trade economic scenario across the entire Columbia River Basin, including portions of the basin outside of Washington State. Wet, dry, and average flow conditions are shown for both supply (dotted lines) and demand (error bars).

Columbia River Basin Survey

In response to the survey, water mangers throughout the Columbia River Basin suggested that additional summer water is generally needed for future instream and out-of-stream demands. However, efforts to improve flow or aquatic habitat conditions in portions of the Columbia River Basin outside of Washington state typically involve relatively minor changes to management of winter or peak flows at existing projects, rather than new storage projects. Contributing factors include a lack of funding and willingness to pay for water. These types of minor changes to management of winter or peak flows would have limited impact on Washington's overall water supply. The survey results did not indicate a need for WSU's modeling team to dramatically alter flows entering Washington State in this Forecast.

OCR intended that the survey identify opportunities for future collaboration with out-of-state partners. No specific partnership opportunities were identified, but one underlying theme of responses was that a lack of regional and crossjurisdictional communication hampers planning efforts. Thus, improving communication may be a first step to create purposeful partnerships.

Columbia River Treaty
Although not brought out directly in the survey responses, one important issue on the horizon that could dramatically alter the surface water supplies entering Washington state is the re-negotiation of the Columbia River Treaty between the United States and Canada. The 1964 Treaty provided for the construction of four dams in the upper Columbia River Basin that more than doubled the amount of reservoir storage in the basin: Libby in Montana, and Duncan, Keenleyside, and Mica in Canada.  These four dams are operated to benefit downstream hydropower generation and flood control. According to the U.S. Army Corps of Engineers, the dams provide billions of dollars of benefits for the two countries. The Treaty has a 2014 opt-out clause that allows either country to notify the other that they intend to terminate the treaty in 2024. Since the treaty was originally ratified, the emergence of additional complex issues such as future needs for anadromous and resident fish, irrigation, recreation, municipal water supply as well as power and flood control has both sides examining whether or not new operating rules would provide additional benefits to both countries. If notification to terminate is given by either side in 2014, it could radically change the context in which OCR is working to meet water demands in the Columbia River Basin. This issue will be addressed in detail in the 2016 Forecast.

Tribal water rights may also have the potential to alter water supplies in the region. Quantification of these rights involves complex legal issues beyond the scope of this Forecast. Further quantification of these water rights could impact water supplies, particularly those available for meeting instream demands.

Columbia River Basin Agricultural Water Demand

The 2030 forecast of demand for agricultural irrigation water across the entire Columbia River Basin was 13.6 million acre-feet per year under average (50th percentile) flow conditions, with the range of low and high estimates under different weather conditions from 13.1–14.1 million acre-feet per year (20th and 80th percentile) (see Supply & Demand comparison figure). When compared to average historical (1977–2006) conditions, this represented an increase of 0.33 million acre-feet, or approximately 2.5% above estimated demands for the historical period of 13.3 million acre-feet per year (Table 1 below).

Table 1: Top of crop agricultural demands under the baseline economic scenario
  Historical  (1977-2006) million acre-feet per year 2030 Forecast
million acre-feet per year
% Change
Entire Columbia River Basin 13.3 (12.6–13.9) 13.6 (13.1–14.1) 2%
Washington Portion of the Columbia River Basin 6.3 (6.0–6.5) 6.5 (6.2–6.6) 2%

Top of crop agricultural demands under the baseline economic scenario (medium domestic economic growth and medium growth in international trade), excluding conveyance losses, in the Columbia River Basin in the historical and 2030 forecast period. Estimates are presented for average years, with range in parentheses representing wet (80th percentile) and dry (20th percentile) years.

These demand results should be thought of as the upper bound of "top of crop" water demand under the medium growth, medium trade scenario, assuming no change in the land base for irrigated agriculture. This is because the 2030 forecasted value represents water demand after changes in crop mix have occurred in response to changes in the domestic economy and international trade flows. As described more fully in the "Overview of the 2011 Forecast," constraints on water availability (including physical availability or regulatory curtailments) are assumed to result in deficit irrigation of nearby less profitable crops; other producer responses that would minimize the production impacts of water shortages are outside the scope of this Forecast. This would include strategies such as changes in crop mix to favor less water intensive crops, or investments to increase the efficiency of irrigation.

Results for the Washington State portion of the Columbia River Basin are similar, suggesting that 2030 irrigation demands will be roughly 1.9% above historical. This change is due to a combination of two factors: climate change and changes in crop mix driven by the economic scenario considered. Considering the climate impacts of temperature and precipitation variations alone on the irrigation demand, there is a 3.7% increase in demand. When economic impacts resulting in a new crop mix are considered in addition to the climate effects, the increase in demand reduces to 1.9%.

These changes in total irrigation demand do not include additional surface water demands that may result from the need to supply water to agricultural producers in the Odessa area who currently receive groundwater. These demands were treated as groundwater demand in the historical case, and surface water demands in 2030. In the 2030 forecast, this area represented 240,000 acre-feet per year of surface water irrigation demand.

Impact of Variations in Trade and Growth Predictions on 2030 Irrigation Water Demand in Washington

The irrigation demands presented above were run under a medium growth, medium trade scenario, reflecting 'most likely' future conditions. Low and high alternate scenarios captured the range of possible future economic conditions within Washington, considering both growth of the domestic economy, and growth in international trade in agricultural goods. Forecasting methods are described in the "Overview of the 2011 Forecast." Overall, the low, and medium economic scenarios forecasted an estimated 6.5 million acre-feet of average irrigation demand and the high medium scenario forecasted an estimated 6.4 million acre-feet of average irrigation demand within the Washington portion of the Columbia River Basin, assuming that the extent of irrigated acreage stayed constant (Table 2).

Table 2: Top of crop agricultural demands under low, medium, and high economic scenarios
  2030 Forecast Under Varied Economic Scenarios
million acre-feet per year
Low Medium High
Washington Portion of the Columbia River Basin 6.5(6.2–6.6) 6.5(6.2–6.6) 6.4(6.2–6.6)

Top of crop agricultural demands under the three economic scenarios (low, medium, and high), excluding conveyance losses, in the Columbia River Basin for the 2030 forecast period. Estimates are presented for average years, with range in parentheses representing wet (80th percentile) and dry (20th percentile) years.

Over the range of scenarios considered, variation in assumptions about economic growth generally resulted in modest changes in production relative to the impact of international trade. Domestic economic growth was projected to be 1.6% per year in terms of real income per capita for the "medium" scenario, 1.3% under the low scenario, and 1.8% under the high scenario. In essence, domestic growth impacts water demand because more consumers with more money to spend on food places upward pressure on food prices, incentivizing producers to increase production. Population growth generally impacted all crops equally while income growth had a relatively larger impact on high value crops such as cherries and wine grapes. However, these changes still caused relatively small changes in total irrigation water demand. Although many of the crops most sensitive to changes in income are irrigated, including apples, wine grapes, and cherries, they each occupy 200,000 acres or less in Washington. This is a relatively small area compared to wheat, cropland pasture, and forage crops, which together account for more than 80% of all cropland in the state. Among these latter crops, non-irrigated acreage will not significantly impact irrigation water demand, although it may influence water supplies by impacting surface water runoff quantities.

Variation in assumptions about international trade had a more significant influence on crop mix than assumptions about domestic economic growth, with greater influences generally for high-value crops. There was little variation in irrigated wheat production between the low and high scenarios, based on the expectation that export demand for wheat will remain fairly steady.* In contrast, fruit and vegetable production varied more between low and high scenarios, based on robust growth of export demand for these crops over the last decade.** In contrast to most fruit-based products, demand for Washington wine grapes and wine production is expected to be primarily dependent on growth in the domestic rather than foreign markets. For alfalfa, traditional exports to South Korea, Taiwan, and Japan are expected to stay at historic levels although there is some possibility that exports to dairies in other parts of Asia could become an important new demand center.

Impact of Additional Water Capacity Development and Cost Recovery for New Water Provision on Forecast 2030 Irrigation Water Demand in Washington

The baseline scenarios presented in this Forecast do not include any changes in water management. This was done to isolate the impact of changes due to larger market forces from those resulting from state level policy. It is also a prudent approach given the legal, political, and financial obstacles to changes in water management. As described in the "Overview of the 2011 Forecast," in comparison with that baseline, OCR asked for analysis of a number of scenarios that included development of approximately 100,000, 200,000, and 500,000 acre-feet of additional water capacity at specific locations in the state, and potential recovery of development costs at a variety of prices, including zero. In interpreting the results of this analysis, it is important to recognize that this Forecast does not include benefit-cost studies for any particular water development projects.

Projects associated with the medium water capacity scenario of 200,000 acre-feet per year were estimated to lead to approximately 62,000 acres, including both newly irrigated lands, and replacement water for acreage in Odessa currently irrigated by groundwater. The economic impacts associated with production on this acreage would generate an estimated agricultural output of $169 million, or about $2,700 per acre. This estimate does not subtract the value of production if land were currently under dryland cultivation. Total economic impacts of the additional production were estimated with the Implan® economic input-output model to be an additional $120 million in indirect and induced effects.***

The economic impact of this increased production was estimated to be 6,600 jobs, which included employment related to crop production and food processing industries. State and local tax impacts were estimated at about $37 million, with most of this coming from indirect business taxes, including taxes incurred in the ordinary operation of business (such as sales taxes, excise taxes, and property taxes).**** The values of output and other estimated economic outputs are reported in current terms, reflecting the fact that the input-output model shows the current economy in terms of wages, production technologies, and many other factors. To put this into perspective, there are approximately 62,000 jobs in Washington directly related to crop production and almost half are in fruit farming. There are an additional 31,000 jobs in agricultural support activities and 12,000 jobs in relevant food processing industries.

Information on the disposition of agricultural production to specific processing industries is not generally available so it was necessary to make a few general assumptions to include processing industry impacts. According to USDA statistics about 18% of apple and cherry production enters into processing. Thus, 18% of new fruit production was assumed to be processed within the state, in the canning industry. For vegetables, potatoes, sweet corn, and onions constitute more than 90% of Washington's vegetable acreage. About 75% of potato production is allocated to the frozen food industry. Nearly all sweet corn production is processed. Data is not available for onions, though it is likely that less are processed. Combining all this information, it was simplistically assumed that 75% of the additional vegetable production would be processed within the state and that all of it went towards frozen foods (though in reality there is some processing in other industries such as snack food manufacturing). Additional wine grapes were assumed to be processed in Washington by the wine industry.

While not quantified, it is recognized that maintenance of and improvement to instream flows would have positive economic impacts on tourism and recreation, generating additional jobs and tax revenues.

Results for the low and high water capacity scenarios will be available in WSU's technical report (Ecology Publication 12-12-001).

Cost recovery scenarios considered various possible scenarios of prices that could be charged for new water capacity for cost recovery purposes ($25, $100, and $200 per acre-feet per year). These prices correspond respectively to the range of prices being charged for projects currently in development, a higher price that has been charged elsewhere for water projects, and a possible high price in the future. The total amount that could be generated for cost recovery purposes was determined by discounting the stream of payments received over time into a single present value. At low prices, agricultural producers are likely to use all water made available because their net revenue would still be greater by irrigating than under dryland production. At higher prices it is possible that not all of the water will be used.

As is typical for this type of analysis, results varied significantly depending on the assumption of the discount rate, which is usually based on either yields of long-term government bonds (low estimate) or on the rate of return on capital in private markets (high estimate). An assumption of a lower discount rate leads to a higher present value. Depending on whether the discount rate considered is 2, 4, or 6%, cost recovery from charging $25 per acre-feet for 200,000 acre-feet in perpetuity would be $250 million, $125 million or $83 million, respectively. Full results of the pricing scenarios analysis will be available in WSU's technical report (Ecology Publication 12-12-001).

* Exports of Washington wheat have fluctuated around an average of $380 million for the last decade, and tend to spike when there are significant weather induced shocks to other major wheat growing regions. Climate change predictions suggest that weather-induced crop reductions could become more common in places like Russia and Australia, elevating the average level of Washington exports somewhat. (back)

** Fruit and vegetable exports fruit and vegetable exports have grown at approximately 5% per year for fruit and 3% for vegetables over the last decade, with simultaneous growth in domestic markets. (back)


*** This estimate included additional economic activity generated through backward linked industries, such as machinery repair and fertilizer sales, and spending throughout the rest of the economy that are impacted by additional household income. (back)


**** Total taxes also included employer contributions to social insurance, proprietor income, indirect business tax, taxes on household income, and taxes on corporate profits. (back)



Columbia River Basin Municipal Water Demand

The forecast of municipal demand in Washington should be understood within the context of likely increases in demand throughout the Columbia River Basin. U.S. Census estimates show population growth over the next 20 years in Idaho (25.6%), Oregon (26.2%), and Montana (5.6%). Without concerted conservation efforts, population growth will certainly increase demands on water flowing into Washington state. Idaho has not released county-by-county growth projections, and it is difficult to predict which additional municipal demands will be met from deep groundwater supplies which would not impact surface water supplies. However, it is safe to assume that additional demands in Idaho will reduce inflows into some parts of Washington. A study of the Spokane River Basin by the state of Idaho projected that they would place an additional demand of 31 cfs on the river by 2060.

WSU projected domestic and industrial diversion demands, excluding selfsupplied industries, of 569,000 acre-feet per year in Washington in 2030, an estimated 26% increase over 2010 (see table below). This increase of approximately 117,500 acre-feet per year compared to 2010 is driven by expected population growth. Per capita demands varied considerably throughout eastern Washington, with an average total demand (including system losses) of approximately 277 gpcd. These results are in line with a 2005 U.S. Geological Survey study of domestic water use, which estimated 285 gpcd.* Forecasting methods are described in the "Overview of the 2011 Forecast."

Municipal diversion demands for the Washington state portion of the Columbia River Basin.
(acre-feet per year)

2030 Forecast
(acre-feet per year)

% Change
Washington Portion of the Columbia River Basin 452,000 569,000 26%


Total consumptive demands for 2030 for eastern Washington were estimated to be 291,000 acre-feet per year in 2030, compared to 232,000 acre-feet per year in 2010. This represents approximately 51% of the total diversion quantity, which may be high compared to other investigations, but nevertheless, represents an initial estimate. These amounts were distributed evenly throughout the year, with no attempt to account for seasonal variations in water use. Future analysis should examine monthly variations, and should also utilize the OFM's WRIA level population estimates to improve the assumed distribution of current and future populations by WRIA.

These estimates did not include the potential impacts of system repairs or conservation efforts on future demands. As an example of the impact this could have, eliminating system losses would result in a net savings of nearly 56,000 acre-feet per year currently and 70,000 acre-feet per year by 2030. Of equal importance is the potential impact of conservation practices. Reducing current demands by 10% would reduce current diversion requirements by 45,000 acre-feet per year and projected future diversion demand by 57,000 acre-feet per year and future consumptive use by approximately 29,000 acre-feet per year.

*Lane 2009, op. cit. (back)

Columbia River Basin Instream Water Demand

Forecast changes in surface water supply timing are likely to increase the challenge of meeting instream demands throughout the Columbia Basin river system. Increases in out-of-stream demands within and outside of Washington by 2030 are also likely to make it more difficult to meet instream demands by 2030. Lower flows, particularly in the summer and early fall, could negatively impact threatened and endangered fish in the Columbia River Basin (Figure 1), as well as other fish important to the culture and economy of eastern Washington.

Distribution of fish listed under the Endangered Species Act in the Columbia River Basin.

Distribution of ESA listed fish

Figure 1. Distribution of fish listed under the Endangered Species Act in the entire Columbia River Basin.

Several factors have the potential to impact future water supplies for meeting instream demands in ways that are difficult to predict, and thus were not feasible to capture in this analysis. The possibility for re-negotiation of the international Columbia River Treaty and unquantified tribal water rights, both discussed with water supply results earlier in this section, could change the amounts and timing of water available to meet instream needs in the Columbia River mainstem.

As described in the "Overview of the 2011 Forecast," OCR's database of historical flow information provides site-specific information on historic flow levels, drought occurrences and how often instream flow rules are or are not met for tributaries to the Columbia River in Washington. For example, by graphing the 1963-2009 flows of the Wenatchee River at Monitor gauge (USGS # 1246200) (Figure 2) it is shown that

• Historic mean annual flows generally varied between 1.5 and 3 million acre-feet.

• Over the last 30 years, dry years (20th percentile or lower) occurred 6 times, with the worst stretch being 3 consecutive dry years in 1992-1994. During this same time period, the availability of water during dry years worsened (18% decrease).

• The instream flow rule is almost always met in average years except in late summer. In dry years, the instream flow is met in early summer and in the winter.

• The magnitude of unmet instream flows is small in this location. For example, in average years, the instream flow deficit for the entire year totals 2,000 acre-feet. The total annual deficit grows to 84,000 acre-feet in dry years.

• Water is available in-basin that could be used to address these instream shortages through OCR-funded projects (e.g. storage, conservation, or pump exchanges). At Wenatchee at Monitor, the annual amount of water surplus to instream flows during an average water year is 1.5 million acre-feet.


Comparison of actual flows

Figure 2. Comparison of actual (not modeled) historical flows (1963-2009) during dry (20th percentile), average (50th percentile), and wet (80th percentile) years to the instream flow rule for Wenatchee River at Monitor.

Columbia River Basin Hydropower Water Demand

As described in the section "Overview of the 2011 Forecast," the hydropower demand forecast focused on a review of projections carried out by power planning entities throughout the Columbia River Basin. The Northwest Power and Conservation Council projected average electricity demand for the entire Pacific Northwest (inside and outside Washington state) of 25,275 MWa, roughly 6,000 MWa higher than in 2010 (range of 22,010-27,761 MWa).* Based on WSU's review of this and other regional documents, and interviews with several PUD officials and Avista, utilities throughout the U.S. portion of the Columbia River Basin expect to be able to meet projected steady growth in peak winter and summer energy demands through conservation and integration of other energy sources. New non-hydroelectric projects will likely be needed to meet other requirements such as those in I-937. Several power entities also mentioned concerns about the potential for climate variability (discussed in the section "Climate Change and the 2011 Forecast") and possible renegotiation of the international Columbia River Treaty (discussed with water supply results earlier in this section) to disrupt or reduce hydropower generation capacity.

In the Canadian portion of the Columbia River Basin, B.C. Hydro expects that demands may grow as much as 40% across British Columbia. Conservation and transmission improvements are described as playing an important role in meeting this anticipated new demand. Beyond that, Site C Clean Energy Project (outside the Columbia River Basin, on the Peace River), if built, could provide up to 1,100 megawatts (MW) of capacity (450,000 homes). Additional capacity at Mica Dam on the Columbia River is anticipated to play a smaller role in meeting new demand; BC Hydro is currently working to add two new generation units (for a total of six). These additional units would not always operate, so although they will provide additional peak capacity of 1,000 megawatts, they are anticipated to serve only 80,000 homes.

Power entities in the Columbia River Basin feel it is unlikely that new storage reservoir projects will be needed solely to meet growing power demands within the next two decades, though they may be needed to help meet growing future surface water supply demands. If additional storage projects are built for water supply purposes, pumping associated with the storage will likely create additional power demands, justifying the expansion or upgrading of hydroelectric facilities. It may also be feasible to generate power as an ancillary benefit at a new storage project, if one is built.

Grand Coulee Dam spillway and power transmission lines

Grand Coulee Dam spillway and power transmission lines

* NWPCC 2010, op. cit.



Definitions of terms 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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