The Cooling Power of Trees

How a natural infrastructure test case in Medford helped kick off a more sustainable approach to water management.

Medford sits near the Rogue River, one of our state’s most well-known and stunning landscapes with a reputation for strong salmon runs and pristine whitewater. Medford, like cities all over Oregon, treats millions of gallons of wastewater every day from its residents. Where does all of that treated wastewater go?

It gets discharged back into the Rogue River.

Returning the water we use at home, in our yards, on farms and in businesses back to our rivers clean and cold enough to meet the needs of salmon and keep rivers healthy is the responsibility of all Oregonians. Cities have built hard infrastructure like treatment plants and chillers to meet Clean Water Act requirements, but it’s not always enough or an affordable solution for every problem, and often just addresses one goal.

When the City of Medford started exploring how it would meet its temperature requirements so that warm treated wastewater didn’t raise the overall temperature of the river, officials considered several options. Mechanical chillers could meet the goal of avoiding warm water releases, but they are energy intensive, contribute to climate change, have a limited lifespan and would have a limited effect on the overall health of the river – plus it was the most expensive option for ratepayers. A second option, storage lagoons that could hold water until it was the right temperature, would require disturbing large areas of land.

In the end, the City of Medford chose an approach that would make them a case study in natural infrastructure solutions, create net environmental benefit and save residents money.

Natural infrastructure is an approach that respects, reclaims and restores the natural benefits of functioning ecosystems to achieve or assist with the same goals as traditional built infrastructure like treatment plants and dams. In our upcoming blog series, we’ll share several examples of what this approach looks like to help you see the opportunities in prioritizing more natural infrastructure solutions across Oregon.

How did Medford meet its wastewater temperature requirements using natural solutions?

Medford Water Quality Trading Video from The Freshwater Trust on Vimeo.

With the help of The Freshwater Trust, Willamette Partnership and others in the Rogue Basin, the City of Medford offset its warm wastewater by investing in upstream river restoration that would provide a bigger benefit to the overall health of the river. By paying private landowners to plant trees along the river, the City and its partners will be able to restore close to 30 miles of riparian area with 500,000 trees that will provide effective shade to the river, cooling the water temperature and helping meet water quality goals throughout the system as they mature.

The City agreed to offset its temperature impact of 300 million kilocalories (kcals) per day at a rate of 2 to 1. To do this they planted trees upstream that would block solar energy from heating the river. Studies show that after 20 years, planted buffer areas 45 feet wide can block 18.8 million kcals per day per mile. Once the water quality benefits are verified, they become credits, which can be used by the City to meet regulatory requirements. This is called Water Quality Trading, and it’s an example of a natural infrastructure approach that can be employed in many Oregon watersheds.

Since launching the project, partners have planted native vegetation such as Ponderosa Pine, Black Cottonwood, Big Leaf Maple, Oregon Ash and White Alder on upstream property held by participating landowners. Beyond blocking solar energy, these riparian restoration efforts help reduce phosphorus in the river by 37 lbs/year, nitrogen by 245 lbs/year and sediment by 83,900 lbs/year.

In addition to saving ratepayers $12 million compared to building mechanical chillers, the Medford Water Quality Trading program has restored fish and wildlife habitat, provided air quality and climate change mitigation benefits, helped stabilize streambanks and prevent erosion, and brought back the natural water filtering power of buffers on the banks of one of Oregon’s most beloved rivers.

These types of sustained restoration projects require large-scale planning and long-term maintenance, which creates job opportunities in fields such as engineering and wildlife biology, plant nurseries, heavy equipment and construction companies, and rock and gravel companies. In fact, a study done on a five-county area of Southwestern Oregon showed that total investments in 2,350 restoration projects supported 727 – 1,018 jobs. The same study found that a $64.3 million investment in restoration work generated an estimated $113.7 – $141.1 million in economic output, 80 percent of which stays in the local area.

But natural infrastructure projects are not without challenges.

Research by Willamette Partnership showed that the processes associated with permitting and planning Water Quality Trading initiatives can be arduous and technical, requiring capacity and financial resources. Once the project has been installed, regular maintenance must be performed to achieve the compliance targets. Maintenance must ensure that native plants continue to grow and are not overcome by non-native or vigorous weedy plants. Another challenge is the issue of scale. In order to be feasible on the large-scale, many miles of streamside restoration need to be coordinated requiring even greater capacity and a more robust trading market. That’s where turnkey partners like The Freshwater Trust come in to help municipalities and permit holders coordinate all of the project details.

Oregon Environmental Council’s water team is working with utility associations, state agencies, natural infrastructure experts and conservation organizations to better understand the barriers to implementing more nature-based solutions as we tackle our water challenges.

We believe that by incorporating more natural infrastructure approaches into our state’s toolkit for water management, we can accomplish more, benefit our communities and ecosystems, and pass savings along to Oregonians.

The next blog in our natural infrastructure series will showcase a nature-based stormwater solution in industrial Clackamas County. Stay tuned for more innovative approaches to Oregon’s water challenges!

Special thanks to David Mueller, PSU Public Policy graduate and OEC spring 2020 volunteer intern, for researching and writing about the Medford Water Quality Trading program as we kicked off our work on natural infrastructure. 
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