Local river data illustrates TMDL challenge
Meeting held last week regarding the Malheur River Basin
By Larry Meyer
Argus Observer
Tuesday, November 25, 2008 12:20 PM PST
| |
| On a fall afternoon, the Malheur River nears its confluence with the Snake River. All reaches of the river were found to be meeting standards for dissolved oxygen. |
ONTARIO — Participants in a meeting last week designed to discuss portions of the Malheur River Basin Total Maximum Daily Load document developed a simple conclusion — showing a particular river is functioning properly regarding dissolved oxygen and chlorophyll is probably the best result officials can hope for or expect.
The document is currently under construction by the Oregon Department of Environmental Quality to address basin-wide water quality issues.
A TMDL is the maximum amount of any one pollutant a body of water can carry and still meet federal water quality standards. Pollutants may include nutrients, sediments and chemicals. One of the requirements of the federal water quality law behind the TMDLs is implementation of pollution-reduction blueprints by any entity deemed responsible for runoff or discharge into area waterways.
In his report, John Dadoly, DEQ basin coordinator, said waterbodies in the Malheur River Basin are listed as water quality limited because of low dissolved oxygen and excessive chlorophyll concentrations, as well as high concentrations of phosphorus.
Dadoly said the purpose of the TMDL document is to verify the validity of the listings and to determine the source of the pollution. In the case of dissolved oxygen and chlorophyll, the listings were found not to be entirely valid.
While low dissolved oxygen was listed as a problem for the whole year in the basin, Dadoly said monitoring data reviewed during the TMDL development indicated the dissolved oxygen standards are actually being met. Also, he said, that chlorophyll criteria was also being met most of the time in the Malheur River and its tributaries.
However, the total phosphorus data shows the high concentrations begin in the headwaters of the Malheur River and may be related to riparian conditions and associated soil erosion levels. The complaints by local residents involved in the TMDL processes have been the phosphorus levels exceed the water quality standards long before it reaches farming areas that could affect water quality and are naturally occurring.
Only in the upper reaches of the Malheur Basin does water meet the standard of .07 milligrams per liter. The lower Malheur River, including monitoring sites at Riverside and Juntura, does not meet that standard anywhere.
Clint Shock, a member of the Malheur Watershed Council, said the phosphorus levels are heavily affected by storm events.
“We need to focus on things we can improve,” he said.
Dadoly concluded that controlling erosion may a be help in reducing phosphorus.
