Temperature TMDL for Columbia Mainstem
by Mike O'Bryant
Parkin said that dams have a much greater impact on temperature
than either point sources of temperature pollution or the river's 193 tributaries.
Discharges from factories along the mainstem Columbia and lower Snake rivers have very little impact on the rivers' temperature, but the 19 dams on the two rivers do.
That is what the Environmental Protection Agency, Northwest tribes and three Northwest states are finding as they work through a study that will ultimately determine how much pollution in the form of higher temperatures the river can withstand and still achieve water quality standards set by the states.
The EPA, states of Washington, Oregon and Idaho, and tribes are jointly preparing a Total Maximum Daily Load (TMDL) for temperature for the Columbia River from the Canadian border to the ocean and for the lower Snake River from the confluence of the Salmon River to the river's confluence with the Columbia River.
"The states, the tribes and the EPA three years ago came together to do a mainstem TMDL and, happily, today we have something concrete from the work we've been doing," Russell Harding of the Oregon Department of Environmental Quality said this week at the last of three public workshops. EPA and the states had also sponsored workshops in Lewiston, Idaho Sept. 25 and Kennewick, Wash., Sept 26. While the TMDL is incomplete at this stage, the players expect to release a draft TMDL in early November and a final temperature TMDL by June 2003.
Harding said that the federal Clean Water Act (1972) requires that every river not in compliance with state water quality standards must have a TMDL, which defines the maximum allowed pollution for a water body and allocates pollutant loads among the various sources. The Columbia River is on Washington's and Oregon's 303(d) list of water quality impaired bodies of water for temperature and dissolved gas, and the lower Snake River is on the Washington and Idaho 303(d) list. While it would traditionally be the states' job to develop the TMDL, that duty was handed over to the EPA because the rivers touch on three states as well as the Canadian border.
A recently-completed fact sheet prepared by the EPA (available on the Internet at www.epa.gov/r10earth/columbiamainstemtmdl.htm) about the differences in water temperature between the free flowing river and the river impounded by dams says that water temperature on the river frequently exceeds state and tribal water quality standards. In fact, the frequency of those annual violations has increased from 3 percent without the dams to 13 percent with the dams in place.
"The dams appear to be the major cause of warming of the temperature regimes of the rivers," the fact sheet says.
Richard Parkin of the EPA said researchers don't know exactly what the river conditions were before the dams, so he and others had to model the rivers to simulate natural conditions, arriving instead at a site potential, which is the calculated temperature that would occur if the effects of human activity on temperature was eliminated.
"Water quality -- in this case temperature -- is generally tied to natural conditions," Parkin said. "We didn't have much information on natural conditions." Missing from the EPA information was natural meteorology data and natural river flow data. "Instead, we take the water as it comes to us from Canada and try to determine what would the temperature be if there was no human activity. It's a surrogate measurement for the natural."
He said the natural river temperature fluctuated more than the impounded river does, with temperatures rising during the day, but falling lower after the sun goes down as the air temperature cools. However, an impounded river holds the heat longer and temperatures fluctuate less. The impounded river, he said, would deviate most from the conditions of a natural river beginning in late summer.
In a free flowing river, water temperatures would respond more to weather than the impounded river. "Cooling weather patterns tended to cool the free flowing river but have little effect on the average temperature of the impounded river," the fact sheet says. "The free flowing river water temperatures cooled more quickly in the late summer and fall."
But, the U.S. Army Corps of Engineers said in its testimony in a recent lawsuit by the National Wildlife Federation that temperatures today are lower than the natural river, said Glenn Vanselow, executive director of the Pacific Northwest Waterways Association. "Your graphs show that the river is warmer," he said.
"Yes, our analysis shows that in some years the natural river does model hotter at some times," Parkin said.
"They may factor in releases from Dworshak (Dam) to achieve the load allocations in the future," said Mike Herold of the Washington Department of Ecology.
"Our work is trying to better refine and bring better understanding" to the issue, said Mary Lou Soscia of the EPA.
What this comes down to for the largest river in the United States with a proposed temperature TMDL, is that the TMDL will allocate no measurable increases to dams, but will allow a small increase resulting from human activity for point sources of temperature pollution, such as factories or sewage treatment plants located along the river. After the TMDL is final, the temperature goals for point sources of pollution for the mainstem Columbia River will be a maximum of 0.14 degrees Centigrade over the site potential temperature if it exceeds 20 degrees C, or 1.1 degrees C if the site potential temperature is less than 20 degrees C. Where salmon spawning occurs (above river mile 112) between Oct. 1 and May 31, the temperature goal is 0.14 degrees C if the site potential temperature exceeds 12.8 degrees C.
Of the more than 100 facilities with waste load allocations, 95 that have very little temperature impact on the river will be grouped in one of 15 river reaches and given group allocations, while 11 separate facilities will be given individual allocations, according to Parkin.
If one of the facilities wants to increase its discharge or a new facility asks for a discharge permit, it would be up to the states to decide how much room there is in the allocation for that facility, Parkin said. Or, according to Herold, the point source could arrange to trade with other point sources on the reach.
Parkin said that dams have a much greater impact on temperature than either point sources of temperature pollution or the river's 193 tributaries. Discharges from either are easily absorbed into the much larger Columbia and Snake rivers and limiting the point sources would result in limited improvements at the dams, he said.
In addition to the temperature TMDL, Oregon and Washington submitted to EPA in September a TMDL for total dissolved gas (TDG) for the lower Columbia River. Washington is developing a TMDL for gas in the mid-Columbia River and the lower Snake River and the EPA is working with tribes on a gas TMDL for tribal waters, such as Lake Roosevelt, which backs up behind Grand Coulee Dam in the upper Columbia River.
EPA Region 10: www.epa.gov/r10earth/index.htm
Columbia/Snake River TMDL Web Page: www.epa.gov/r10earth/columbiamainstemtmdl.htm
Office of Water TMDL Home Page: www.epa.gov/OWOW/tmdl/index.html
Oregon DEQ: www.deq.state.or.us
Washington DOE: www.ecy.wa.gov
Idaho Department of Environmental Quality: www.deq.state.id.us
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