2040 Temperature Check on One of North America’s Biggest Watersheds

More water earlier and less snow – the Columbia River Basin’s water health was recently forecast into 2040 as the result of a two-year study across the Washington State Department of Ecology, Washington State University, University of Utah, State of Washington Water Research Center, and Aspect Consulting in the 2021 Long-Term Water Supply & Demand Forecast.

Photo Credit: Robyn Pepin, Aspect Consulting. Columbia River near Entiat

This mammoth water evaluation project – done every five years since 2006 – looks across the Columbia River Basin, which includes 34 eastern Washington watersheds. Hydrological modeling, economic modeling, regulatory context, remote sensing, surface water and groundwater monitoring and more all are studied to predict the future of water for agriculture, population growth, and instream flow health under a changing climate in this critical basin.

Forecast Insights for the 4th Largest Watershed in North America

Image Source: 2021 Columbia River Basin Long-term Water Supply and Demand Forecast

The Columbia River Basin is the 4th largest watershed in North America, running down from headwaters in Canada and mainly into four states – Washington, Oregon, Idaho, and Montana. Some notable details and insights from the recent forecast include:

  • Wet months getting 15% more water and dry months getting 28% less water

  • Earlier planting dates and more heat stress during the hot months

  • 17% higher population growth across Washington state leading to increases in demand for residential water and hydroelectric power

  • Trends in groundwater levels across the last 20 years were predominantly declining across the basin. The steepest declining trends correspond with the most heavily pumped layers and areas such as the Grand Ronde aquifer in the Odessa Sub Area and the Wanapum aquifer in parts of the Yakima Basin and Horse Heaven Hills.

Expected changes that will influence future water supplies and demands. These expected trends inform the scenarios explored in the 2021 Forecast.

Graphic Source: 2021 Columbia River Basin Long-term Water Supply and Demand Forecast

A 2040 Water Crystal Ball: Water Retiming Means More Water Earlier

Among the many takeaways in this report is the impact of climate change on water cycles. Chief among those is the prediction that peak surface flows – that feed the historically typical April – October agricultural season – will begin earlier, thus leaving less water available later in the summer when demand for that water is higher. Snowpack – the Pacific Northwest’s natural water reservoirs – will likely melt earlier because of warmer temperatures.

This ripple effect will influence agriculture starting earlier in the growing lifecycle; instream flow challenges with higher temps for fish habitat; and populations in arid regions will likely be incrementally more dependent on groundwater to serve future water supply. Declining groundwater trends mean that alternative water supplies may not be available in some areas so additional solutions are needed.

Time (in years) until the average available saturated thickness has declined by 25% in at least one aquifer layer in each groundwater subarea.

Image Source: 2021 Columbia River Basin Long-term Water Supply and Demand Forecast

State-of-the-Science Research

Aspect teamed with the project team and the scope of the science and monitoring over the last two years is impressive. A team of scientists and engineers looked at remote sensing and telemetry data across eastern Washington; climate change forecasts; population growth projections; well logs; and water rights. Some of the months-long study details of that include:

  • Integrated hydrological, river operations, crop production, and municipal, domestic and industrial water demand modeling in 34 watersheds under 34 potential climate change scenarios

  • Groundwater level trend analysis on 670+ wells

  • Automated well log review of over 4,000+ well logs

  • Manual well log review of 300+ well logs

Learn more also at WA Ecology’s project StoryMap here.

Groundwater Models: A Powerful Tool in the Hydrogeology Toolbelt

Meteorologists have them. Economists have them. And so do hydrogeologists. Complex computer models, backed by powerful processing power, help us understand and predict weather, wall street, and water. Indeed, groundwater models as predictive tools to forecast water movement and availability are a critical part of a hydrogeologist’s toolbelt.

Recently, Aspect hydrogeologists Seann McClure and Aaron Pruitt attended and presented posters at groundwater modeling’s premiere conference: MODFLOW and More, hosted in Golden, Colorado.

Seann (left) and Aaron (right) in front of their posters at MODFLOW and More

MODFLOW, the three-dimensional groundwater model developed by the USGS, is the industry standard for simulating and predicting groundwater conditions, and has been used to simulate everything from the impacts of climate change on groundwater/surface water interactions to the fate and transport of groundwater contamination to the intrusion of seawater into deep aquifers due to water supply developments. The conference is held every two years by the Colorado School of Mine’s Integrated Groundwater Modeling Center, and draws an international list of attendees from the consulting, academic, and government spheres to discuss all things MODFLOW and groundwater modeling.

Seann and Aaron each presented a poster describing Aspect groundwater modeling work. 

Applying Modelling Techniques to Evaluate Wetland Restoration Options Next to One of the Nation’s Busiest Airports

Seann’s poster presented on Aspect’s years-long work at Lora Lake wetland restoration, located adjacent to SeaTac Airport. The presentation, Groundwater Modeling to Support Wetland Restoration of a Former Peat Mine, discusses groundwater modeling completed to evaluate alternative cleanup scenarios at a former peat mine-turned-suburban lake located next to the SeaTac Airport’s new Third Runway. The lake has historically received stormwater discharge impacted by dioxin/furans and is being restored to a scrub-shrub wetland to remediate contaminated lake sediments through capping and filling in the lake. The groundwater modeling, sediment cap, and wetland restoration is part of a larger environmental remediation and construction effort led by Floyd|Snider on behalf of the Port of Seattle that also includes excavation of impacted sediments in the neighboring parcel.

Groundwater Modeling to Help Bolster Water Supply Resiliency for the City of Seattle

Aaron’s poster presented Aspect’s work on assisting a large Puget Sound public agency with predicting water supply availability in an urban area. The poster, Solving the Water Supply Puzzle: MODFLOW and Uncertainty in the Context of Mitigated Water Rights, focuses on the complexity of quantitative analysis necessary to satisfy permitting standards under Washington’s water rights regulations. Recent State Supreme Court decisions constrain mitigation options to those that meet a high bar of being “in-kind, in-place, and in-time”. This means any change to water levels or flows in a closed basin, no matter how small, is considered an impairment, and therefore grounds for rejection of a new water right. This stringent benchmark is even more difficult to deal with when it comes to using numerical groundwater flow models. Groundwater modeling requires simplifying assumptions about the system, which adds a layer of quantitative uncertainty on top of this already rigorous standard. In support of Seattle Public Utility’s effort to permit a future groundwater supply source as a component of resiliency planning, Aspect used MODFLOW to explore various water rights permitting strategies to determine the most defensible approach to in-time, in-place, and in-kind mitigation that balances water rights protections with the agency’s need for new water supply options.