July 19, 2010 - Bend Bulletin - Bend's water plans raise concerns about Tumalo
八月 30, 2010
Bend’s water plans raise concerns about Tumalo
Environmentalists worried about long-term health of creek, watershedBy Kate Ramsayer / The Bulletin
Published: July 19. 2010 4:00AM PST
As the city of Bend works on its plans for a $71 million upgrade to its water system, some conservation groups are keeping an eye on what the changes could mean for the health of Tumalo Creek and its watershed.
Bend currently diverts about half of its water from Bridge Creek before it flows into Tumalo Creek, piping it 11 miles into town. But to meet new federal regulations that go into effect in 2012, the city has to treat the water. And along with that new treatment facility, the city is proposing to install a new, bigger pipe and build a hydropower plant at the end.
“The question is, if there’s a hydroelectric facility, does that create an incentive to try to increase the amount of water that’s diverted from Tumalo Creek, and if so, what’s the impact,” said Ryan Houston, executive director of the Upper Deschutes Watershed Council. Less water left in creeks can lead to warmer water temperatures, which isn’t good for fish and other native aquatic life.
So far, the city has not finalized its plan for the water upgrades, Houston said, so it’s hard to know what specific concerns might arise.
At this point, the proposals for a hydro plant don’t appear to pose threats to watershed health, he said. But he and others are asking questions about what might happen a couple of decades down the road, if the city is able to divert more water from Bridge Creek.
For now, Bend and its consultants are refining the costs and finances of the project, said Tom Hickmann, city engineer.
Call for bigger pipe
Part of the project would involve replacing the two parallel 12-inch water pipes with a single 36-inch pipe. The size increase is designed to increase the energy of the water that flows down the pipe, he said.
When water flows down smaller pipes, it goes fast and is turbulent, decreasing the amount of energy it carries. So, to maximize the amount of energy the water has to turn turbines at the planned hydropower plant, the water system designers called for a bigger pipe.
Bend’s plans do call for diverting some additional water from Bridge Creek, Hickmann said, but that’s not the reason for the bigger pipe. While the city now diverts an average of around 11 or 12 million gallons a day, it wants to take an average of 13 million gallons a day — half of its water rights — with the new system.
“We have the right to more water currently,” he said. “But that’s not the intention of the larger-diameter pipe, and I know a lot of people are really struggling with that.”
The city can’t take all of the water it technically has permission for on paper, because it has junior water rights — meaning that other irrigators take their water first.
Houston, with the watershed council, said that some elements of the water system upgrade project are straightforward and need to be done —like replacing the old pipes, which are falling apart, and treating the water to meet federal regulations. And if the city can generate renewable energy with a hydropower plant, that makes sense as well, he said.
But by putting in larger pipes and building that hydro plant, it opens up the possibility of the city finding a way to divert more water in the future.
“Given that future capacity is there, that does mean that we have to ask the question, will the amount of water change over time?” Houston said.
And if the city does decide it wants to divert more water from Bridge Creek, there’s still the question of whether it could, since its junior water rights put it at the back of the line when the available water is divvied up.
Plus, the analysis has not been done to see what the environmental impacts would be if more water was diverted from Bridge Creek, causing less to flow in Tumalo Creek, Houston said, so conservation groups are also looking to see those questions answered.
“They’re very much crystal ball kinds of questions, and I don’t think anyone knows exactly what it’s going to look like 20 or 30 years from now,” he said.
Working out concerns
The Deschutes River Conservancy is patiently waiting for the city to finalize its plans, said executive director Tod Heisler. And once all the details are worked out, the group will work to ensure there aren’t concerns.
For now, the plan seems to be OK from a water quality standpoint, he said, and the group supports the city.
“Our assumption, which needs to be validated, is that the project would not appreciably affect the diversion of water from the creek,” he said. “And if that’s true, (it) would have minimum impact.”
The city’s junior water rights will prevent it from diverting much more from the creek now, Heisler said. But it does open up restoration possibilities for the future.
In the upper stretches of Tumalo Creek, above Shevlin Park, the water is clean and very cold.
But below Shevlin Park, and below the Tumalo Irrigation District’s diversion, in the summer the water flowing in the creek drops to less than a third of the flow the state sets as the minimum requirement for fish-friendly environments.
Because the lower couple of miles of Tumalo Creek need help, the city could work with the Deschutes River Conservancy and the Tumalo irrigators to put more water in the troubled downstream section, Heisler said. And if that happened, the city could possibly have leeway to take more from the top of the waterway at Bridge Creek, and spin more turbines without greatly impacting the environment.
“We need to fix this (downstream) part, and then everybody’s got a greater opportunity,” he said.
Drill more wells?
The city gets the other half of its water from groundwater wells, and Heisler said he has asked whether it would make sense to drill more wells instead of taking water from Bridge Creek.
Ecologically, the best situation for the Tumalo Creek watershed would be for the city to leave all of the water in Bridge Creek, he said. But the city has said that it is more expensive to pump up groundwater than use the gravity-fed surface water and hydropower solution, Heisler said.
And also it’s better to have different sources of water, in case something goes wrong with one.
“If the creek was your only consideration, we’d say abandon that and go to groundwater,” he said. “But clearly there are many other considerations.”
Kate Ramsayer can be reached at 541-617-7811 or at email@example.com.
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