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Slow the Flow, Spread the Nutrients
Over-grazing. Flooding. Erosion. Fire suppression. Words that conjure up the thrice-told tales of woe in New Mexico and the greater Southwest, with our rivers and creeks morphing from life-giving, nurturing streams of clear, nutrient-rich water to eroding, muddy flashes that throw riparian ecology out of whack and destroy small-scale local economies that depend upon a healthy river.
It’s not that no one has been paying attention, or that no one cares. In fact, even though it rarely makes for news headlines, protecting, managing and restoring our precious waterways is a major industry, and for years environmental advocacy groups have been fighting watershed degradation from cattle grazing in our national forests to toxic mine pollution of our drinking waters.
But actually restoring our many dozens of flowing waterways in NM is a separate challenge, especially in an era of disappearing government funding at every level. Cost is one major hurdle, but creating long-term effectiveness of restoration has been even more challenging, with some planners hauling concrete and steel across the countryside to install industrial-era solutions to such problems as vertical-bank stability, floodplain connection, inundation frequency and riparian-area soil integrity.
But the city of Santa Fe has done something different, again. This time it’s not a festival or an arts project of the kind the city is so famous for but a bold step toward re-creating a sustainable watershed without any heavy-handed industrial engineering. And it seems to be working.
On a recent Friday afternoon, I spent several hours in the Santa Fe watershed with Dale Lyons, watershed manager, and Dr. Peter Stacey,research professor and conservation biologist at UNM and formerly with the Alamosa Land Institute. They are engaged in restoring the Santa Fe River within the watershed. What I found looks like good news for all of NM’s watershed managers and the budget masters responsible for funding them. First, some baseline facts about the condition of the watershed:
The Watershed and Its Protection Plan
- Santa Fe’s 17,384-acre city-managed portion of the upper river basin watershed provides water for 30,000 households and businesses
- Its two reservoirs hold 4,000 acre-feet of water, or 1/3 of the water used annually in Santa Fe
- The upper 10,000 acres located within the Pecos Wilderness Area are primarily mixed conifer and spruce fir
- The lower 7,384 acres are dominated by ponderosa pine and piñon pine-juniper woodlands
- 5,285 acres of the lower area have been treated with mechanical thinning and pile burns to prevent a major fire like the fire in the Jemez Mountains
Once the majority of the thinning was completed in 2006, the task of restoring the three miles of riparian ecology of the watershed between the two reservoirs became a high priority, and a 20-year protection plan was developed collaboratively by the city’s Water Division, the Nature Conservancy, the city’s Fire Department, the Española Ranger District–Santa Fe National Forest, and the Santa Fe Watershed Association. The full plan is available at http://www.santafenm.gov/DocumentCenter/Home/View/4354, and an interesting overview history of the river can be found on the website of the Santa Fe Watershed Association www.santafewatershed.org/
To evaluate the functional condition of the watershed, Dr. Stacey conducted two years of surveys using the Rapid Stream-Riparian Assessment protocol, a quantitative evaluation of two-to-seven indicator variables in five different ecological categories: water quality, fluvial geomorphology, aquatic and fish habitat, vegetation composition and structure, and terrestrial wildlife habitat (detailed protocol information at http://wildutahproject.org/files/images/RSRA_ug_2010V3_wcov.pdf).
The Restoration Project
We started our tour of the central section of the project area at a recently abandoned beaver dam and pond, so I asked about the value of nature’s own engineers to the watershed, which triggered a discussion about the value of complexity in the system, the very quality beavers create by spreading water out from the channel of the river, supporting native riparian vegetation.
As Dr. Stacey described it, a healthy ecosystem, with healthy grass on the slopes, will absorb rain and snow and then release it slowly. With beaver dams, healthy floodplains and grass in the uplands, the soil comes back and a sponge is created that will hold water and prevent loss to evaporation. So the goal of restoring a healthy ecosystem in the watershed is to better utilize what water does fall on the watershed, and as Dale Lyons pointed out, it means the city doesn’t need to build new dams, as the ecosystem itself is a better storage device. Dammed water evaporates, and the annual loss is 15 percent.
What Dr. Stacey had found in his survey was that the riparian corridor above the upper dam was in good shape, but problems existed between the dams due to the regulated stream flow creating uniform channels with no underbank cover for fish, and sediments being washed downstream into the lower reservoir rather than being deposited along the river. As regulated flows don’t allow water to migrate out of the river’s banks to serve the streamside ecology, there had been an invasion of large numbers of pine trees close the bank, closing out possibilities of recruitment of native cottonwood and aspen.
To address these and other issues, a design philosophy was employed that uses the simplest method possible to re-initiate natural processes, without constructing large concrete and steel structures and lots of pushing the earth around. Dr. Stacey described his approach as “…using current ecological theory to develop restoration methods that promote natural recovery processes with the minimal amount of artificial structures and human intervention. Currently, we are working to restore the natural hydrographic in watersheds using logjams and other wooden structure that slow down peak flows, capture sediments, and promote vegetative re-growth, that are self-repairing and reinforcing, and that are designed to function in ways similar to those of natural beaver dams.”This means that the limited intervention is just enough to start the natural recovery process so nature can do the rest.
So what does that look like on the ground, or rather, in the streambed?
This method uses “digger logs” to mimic what happens naturally when a tree falls across the river at certain angle, creating a pool of backup water that eventually fills with sediment, which in turn creates a shallow water ripple area. Then, water falling over the logs digs out a pool on the downflow side of the digger logs.
The sediment dug up on the downflow side of the log jam is then deposited a few feet downstream, creating a sort of sandbar that bends the stream flow slightly, which in turn slows the flow and—importantly—directs the flow toward the other stream bank. This pressure carves out an underbank shelter for fish and contributes to underground flooding, which means more water is absorbed into the soil and migrates outward where it can support native riparian species such as narrow-leaf cottonwood, willow and aspen.
A key design element of this logjam is that the logs are laid across the riverbed at a slight angle, with the downstream end of the logs slightly lower than the upstream. If the logs were laid straight across the riverbed, they would be blown out when stream flow is rapid. Dr. Stacey’s design allows rapid flow to escape over the lower end of the logjam. With this design, you are not really trying to stop a bunch of water as a dam does, just trying to slow it down.
In a healthy stream, about 50% of the stream is made up of an alternating ripple and pool sequence. To mimic that with logjams, the frequency of placement depends on the grade of the stream. If you put them too close together you will create only a sequence of pools, without the crucial ripple patterns in between, where sediment drops out and invertebrates thrive.
As the bottom of the stream channel behind a set of logjams built up through sedimentation, the upstream pool is deepened, which is very attractive for fish habitat. As years progress, there is a chance that the rise of the sediment stream bottom will lift the stream flow back up to where the top edges of the banks are now, allowing for more overbank flooding, supporting a healthy vegetation corridor.
Phase One Structures and Present Outcomes:
Three systems were installed in the river between the two dams about 18 months ago, with each system having between four and seven digger logs. The logjams are being monitored and evaluated for improvements in water quality and the structure of streambed itself, in terms of its ability to filter water, and to create in-stream aquatic habitat for fish and invertebrates. The productivity of the riparian area with regard to vegetation that provides food for wildlife is also a measure of the interaction between the vegetation and the stream.
Each structure is labeled and photographed periodically, and modified SRSA surveys are conducted to document how each logjam works over time.
Both Dale Lyons and Dr. Stacey seemed pleased with the outcomes of this restoration work so far, and the improved diversity of stream flow, sedimentation buildup and healthy ripple and pool sequences were very easy to observe. What had been a uniform, narrow channel was now moving rapidly toward once again becoming the kind of healthy stream that you can find in protected wilderness areas.
As we quietly watched the area around one digger-log installation, a small, gray American Dipper bird appeared, perching briefly on a rock in the stream and then disappearing underwater, searching for invertebrate prey. As it feeds on aquatic insects and their larvae, including dragonfly nymphs and tiny fish or tadpoles, the bird’s appearance confirmed in a beautiful way that this river was indeed coming back to life.
In answer to my question, “Could I do this myself, without your expertise in knowing where to place the logjams, which themselves are quite simple to install?”, Dale Lyons said, “The placement here was quite obvious, where long sections of channel were relatively straight, without a lot of turns or twists or woody debris, and fairly uniform bed material and uniform depth across the channel.
Dr. Stacey added, “We try to take advantage of existing vegetation to anchor the logs instead of bringing in a cement truck to pour pylons, taking advantage of the existing biological structure to provide strength. It’s not rocket science but it’s helpful to know how to take advantage of what you’ve got to work with, including logs from deadfall if available.”
Then I inquired about the cost of installing and monitoring, and Dr. Stacey said, “If you take advantage of natural materials, don’t bring anything into the forest, the bottom-up approach, you can count on no more than $5,000 per installation of 4-6 individual digger-log placements in series.”
This sounded so incredibly reasonable to me that I asked if anyone else in NM is using this technique. He replied that he and a former student who now runs his own firm, Christian LeJuene of Wetwater Environmental Services in Albuquerque, are proposing a big digger-log project in the Jemez National Forest, but that’s the only other one he is aware of at this time.
I then asked if there were an opportunity to run a boot-camp training project to teach people to do this and Peter’s eyes lit up. He said “Hey, if we could do this as a WPA-style project…” and then he looked off in the middle distance, dreaming.
You can follow the progress of this project by contacting Dr. Peter Stacey at firstname.lastname@example.org, and Dale Lyons at email@example.com. 505.955.4204.
Earl James is nonprofit fundraising consultant and the author of the award-winning eco-novel Bella Coola: The Rainforest Brought Them Home. Read excerpts at www.earldjames.com and contact him at firstname.lastname@example.org
About the author
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