What does a stream really need? Its more than meets the eye.
Harvey Locke and Rick Hauer, two very highly respect ecologists and conservationists, write very eloquently on the real nature of Castle and Maroon Creeks, and why the simplistic engineering approach taken by the City and the illusion of protection from minimum stream flows just doesn’t work.
Their column also gave us a warning. We can drain some water from the system, but we can’t go too far before degradation begins. Such degradation often goes unseen, unknown and unheeded, until its too late.
When it comes to river management we tend to see streams as simple conduits, part of an engineered plumbing system for the delivery of water. Engineers, not biologists, determine how and when water is made available. Rivers are treated more as a mechanical system rather than an integrated natural system. The video showing the difference between minimal flows on the City’s web site is a case in point. You see nothing; that’s the intent of the video. It purports that reducing flows to a “minimum” is unnoticeable, causing no harm.
This is nothing more than an illusion, an engineered parlor trick. The real impacts will only appear over time, something the video doesn’t allow or even consider.
Minimum flows are determined by a limited methodology and philosophy, for a state where many still think water left in a stream is wasted. Flat line minimum flows are more a fact of administration engineering than ecology. Healthy streams won’t stay that way when given only a minimum flow for much of the year.
Gravel bed streams like Castle and Maroon Creeks need a reasonable “natural” flow pattern. High spring flows recharge the gravel aquifers underlying the stream, the floodplain and riparian zone. Then through the summer the flow gradually tapers down to the low flows of autumn and winter. A combination of the gradually shrinking flows with unseen water coming in from the surrounding gravel maintains stream health. The channel is only a small expression of the larger unseen stream ecosystem. Locke and Hauer noted, “The riverbed is not like an impermeable sluice box through which the water flows in isolation — rather it is more like a sponge with a channel cut halfway into it where the entire sponge is wet.”
When the sponge dries out from reduced flows the degradation begins. That is what the City’s video demonstration hides.
Castle and Maroon Creeks will still get high spring flows only slightly reduced by the hydropower diversions. But they will lose the gradual reduction in flow through the rest of the year. Rather than being at the minimum for only a month in winter, they will now know the minimum for seven or eight months. The gravel “sponge” will dry out much sooner and for longer as well.
The impacts from this drying sponge likely won’t be seen during the proposed “slow start”. They probably won’t show until after monitoring has ceased and the hydro plant is running at full capacity, under the illusion that the streams are well protected.
Before long degradation in both stream ecosystems will begin to show. Cottonwoods, willows and alders will start dying, with little replacement. New plant species more tolerant of dry conditions but not well suited for the rest of the biotic community will appear. The streambed will become more “cemented” as more sediment than the spring flows can flush builds up. Water temperature will rise with lower flows in summer. Dissolved oxygen will decline. Stressed trout will become more susceptible to disease and find it harder to reproduce as the once vibrant and complex stream ecosystem degrades.
Eventually the ecosystem we know today may no longer sustain itself. It will become a different ecosystem, one less resilient to the growing impacts of climate change.
The above scenario may happen sooner, or much later. Ecosystems are complex and subject to a vast array of interdependent variables. They can be difficult to manage or predict, more so than the mechanical systems of river engineering. It is best to err on the side of caution.
We need to develop energy sources that reduce carbon emissions. But building a traditional hydro plant like those built 120 years ago should be a last option, not a first choice. Climate change itself will likely reduce stream flows. We don’t need to make it worse. We don’t need to destroy the environment in order to save it.
I would hope we’ve learned enough from the mistakes of the past that we might stop repeating them. But maybe we haven’t.