| June 1999 |
ORNL team helps regulators weigh issues in Montana hydro relicensing decision
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| A viaduct channels water for power generation downstream from Madison Dam. |
At issue is the relicensing of several hydroelectric dams in the state, particularly along the Madison River, which flows north from Yellowstone country to eventually form the Missouri with two other rivers. Some environmental organizations want the Madison returned to a pre-dam condition; other groups say the dams are needed for power generation and reservoir recreation. Opinions run strong on both sides, and the Federal Energy Regulatory Commission is using an environmental assessment by ORNL to weigh the merits of the arguments in its decision whether to renew the dams’ licenses.
“There are many competing interests. Some individuals and groups want drastic changes while others prefer to leave things as they are,” says Energy Division’s Bo Saulsbury. “So we’ve conducted lots of public meetings to give all parties the opportunity to comment.” And there is lots of potential for controversy. Saulsbury and Mark Bevelhimer of the Environmental Sciences Division, along with the rest of the ORNL team working on FERC’s Missouri-Madison Hydroelectric Project, take a broad range of facts into account to provide acceptable recommendations on how, they hope, the sides will share the river’s bounty.
The most contentious issue is the effect of the dams on the Madison’s water temperature. The Madison River has two dams. One, Hebgen Dam, is just outside of Yellowstone. The other, Madison Dam, is at about the river’s midpoint near the town of Ennis. A “blue ribbon” 85-kilometer stretch between the Madison and Hebgen dams is a premier trout stream. Fishing is good but not as great below Madison Dam, and trout-fishing organizations blame the impoundment and the resulting gradual downstream warming.
To help them gather information, the ORNL team, which also included ESD’s Mike Sale and Marti Salk, enlisted the help of a computer model developed by the Tennessee Valley Authority. The model, originally developed by TVA-Norris’s Gary Hauser to simulate water flow and quality in the TVA system, was adapted with help from consultant Vahid Alavian to mimic effects on the Montana system under different conditions.
“We modeled the river to include things that would affect temperature—the shape of the channel, shade, flow, elevation and local weather,” says Bevelhimer.
The team looked at alternative proposals by intervening groups: Remove Madison Dam; raise the dam to get a deeper, colder lake; or channel water around the dams to provide cooler water downstream.
“These alternatives would be expensive and have their own environmental impacts,” Bevelheimer says. “What we find sometimes runs against conventional thinking. For example, removing Madison Dam would only have minor impacts on water temperature downstream and small effects on the trout population there. In addition, a valuable reservoir fishery would be lost.
“An interesting twist in our own analysis is that the species of most concern to the fishing organizations are nonindigenous species (brown and rainbow trout) and not the remnant populations of native species like Arctic grayling and cutthroat trout.”
| “What we find sometimes runs against conventional thinking. For example, removing Madison Dam would only have minor impacts on water temperature and small effects on the trout population. A valuable reservoir fishery would be lost.” |
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What the ORNL team has proposed is to send “pulses” of higher water flow through Madison Dam at timed intervals, which would cool the river during hot spells and conserve water for generating power.
That proposal, along with recommendations for protecting a wide variety of resources in addition to fisheries, is included in the two-inch-thick FERC report on the Missouri-Madison Hydroelectric Project (FERC/EIS-0115F), now awaiting final approval. FERC’s Office of Hydropower Licensing will use the volume for the unenviable task of deciding how to make the best use of the Madison River.
“We’ve provided FERC with recommendations that recognize the need to balance power generation with preserving the environment,” says Saulsbury. “If the recommendations are accepted by the FERC commissioners, a new license will be issued complete with numerous measures to protect the river environment and allow for the production of hydroelectric power.”—B.C.
