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What Factors Affect Water Quality?
Related OREGON EXPLORER Info
The Oregon Department of Environmental Quality (ODEQ) has established water quality standards to protect beneficial uses of water. The standards, based on supporting the various beneficial uses, determine the acceptable levels or ranges for water quality parameters, including temperature, dissolved oxygen, and pH. Water quality standards set by ODEQ are reviewed and updated every three years. ODEQ and others monitor water quality parameters in streams and other waterbodies throughout Oregon. Waterbodies that are not within the standards are listed as "water quality impaired." The list of impaired streams is called the "303(d) list," after section 303(d) of the 1972 Clean Water Act. # 303D streams in Umpqua Basin and # in entire state.
For each stream on the 303(d) list, ODEQ determines the total maximum daily load, or TMDL, allowable for each parameter. TMDL is a limit on pollution, developed when streams or other waterbodies do not meet water quality standards. TMDL plans consider both human-related and natural pollution sources. Streams can be de-listed once TMDL plans are complete, when monitoring shows that the stream is meeting water quality standards, or if evidence suggests that a 303(d) listing was in error.
TMDLs for the Little River watershed (Little River drains into the North Umpqua River at Glide) were completed and approved by the Environmental Protection Agency (EPA) in 2001 for the parameters of temperature, pH, and sedimentation. The draft TMDLs for the entire Umpqua Basin (temperature, bacteria, pH, dissolved oxygen, chlorophyll a, nutrients, bio-criteria and aquatic weeds and algae) are in the response-to-comments phase of seeking approval from EPA in 2006.
ODEQ has established acceptable levels or ranges for each of the following water quality parameters. These parameters are important measures of water quality. Each parameter affects one or more of the beneficial uses listed above.
|Water Quality Parameter||Beneficial Use Affected||Importance to Water Quality|
|Aquatic Weeds or Algae||Water Contact Recreation, Aesthetic Quality, Fishing||Aquatic weeds or algae growth can decrease oxygen levels and increase pH, both of which can be harmful to fish. Excessive growth of these organisms can clog navigable waters and interfere with swimming and boating. Aquatic weeds and algae out-compete native submerged aquatic vegetation. Decomposition of weeds and algae can also lead to oxygen depletion.|
( Escherichia coli ) (Freshwaters and Estuarine Waters Other than Shell-fish Growing Waters)
|Water Contact Recreation||Certain bacteria and other organisms cause human illnesses that range from typhoid and dysentery to minor respiratory and skin diseases.|
|Bacteria - Fecal Coliform (Marine Waters and Estuarine Shellfish Growing Waters)||Shellfish Growing and Consumption, Water Contact Recreation||Certain bacteria and other organisms cause human illnesses that range from typhoid and dysentery to minor respiratory and skin diseases.|
|Chlorophyll a||Water Contact Recreation, Aesthetic Quality, Fishing, Water Supply, Livestock Watering||Elevated chlorophyll a levels indicate excessive inputs of nutrients.|
|Dissolved Oxygen||Resident Fish and Aquatic Life, Salmonid Fish Spawning and Rearing||Dissolved oxygen is a basic requirement for a healthy aquatic ecosystem. Most fish and beneficial aquatic insects "breathe" oxygen dissolved in water. Although oxygen concentrations fluctuate under natural conditions, human activities can result in severe oxygen depletion.|
|pH||Resident Fish and Aquatic Life, Water Contact Recreation||Many biological processes, such as everyday metabolism and reproduction, are hampered in acidic (pH too low) or alkaline waters (pH too high).|
|Sedimentation||Resident Fish and Aquatic Life, Salmonid Fish Spawning and Rearing||Sediment may clog and damage fish gills, suffocate eggs and aquatic insect larvae on the bottom, and fill in spaces in the gravel where fish lay eggs. Sediment may also carry other pollutants into waterbodies.|
|Temperature||Resident Fish and Aquatic Life, Salmon Fish Spawning and Rearing||Aquatic life is temperature-sensitive and requires water that is within certain temperature ranges. When temperature exceeds tolerance levels, cold-water organisms such as salmonids become physically stressed and have difficulty obtaining enough oxygen. Prolonged exposure to temperatures outside tolerance ranges will cause death.|
|Total Dissolved Gas||Resident Fish and Aquatic Life||Elevated levels of some dissolved gases can cause impacts similar to elevated pH.|
|Toxic Substances||Resident Fish and Aquatic Life, Drinking Water||Some toxic substances may be harmful, some may undergo chemical changes to become harmful, and some may accumulate in sediments or throughout the food chain to levels that adversely affect public health, aquatic life, or wildlife.|
|Turbidity||Resident Fish and Aquatic Life, Water Supply, Aesthetic Quality||Turbidity is closely related to sediment because it is a measurement of water clarity. In many cases, high turbidity indicates a large amount of suspended sediment in a stream.|
Water quality varies naturally with location and time. For example: the headwaters of streams at high elevations tend to be cooler than wide streams at lower elevations, solar radiation influences stream temperatures throughout the day, and natural differences in climate and riparian vegetative cover cause differences in stream temperature. Some streams are just "naturally" warmer than others. Disturbances such as fires, windthrow, or even debris torrents can influence stream temperature, turbidity, and other water quality parameters. Geology, geomorphology, and climate also influence water quality.
Pollution can be defined as the fouling or making unclean of air or water to the point where beneficial uses are harmed. Water pollution is generally characterized as originating from either "point" or "non-point" sources. Point source pollution is associated with a particular site on a stream and typically involves a known quantity and type of pollutant that can be controlled at the site. An example of point source pollution is effluent from a factory outlet (an end-of-pipe discharge) delivered directly to a stream. Non-point source pollution typically results from multiple contaminant sources over a broader area than a point source. An example of non-point source pollution is fine sediment deposition in a stream bed. The stream may flow through a new housing development, agricultural operations, and forested areas with poorly-maintained roads. All of these activities contribute various quantities of sediment to the stream channel in addition to the natural level of sediment the stream contains.
Non-point source pollution is more difficult to manage and monitor than point source pollution. The volume or "load" from individual sources is difficult to measure. Water quality may not even be degraded at any of the source sites. Instead, the accumulated impacts of multiple sources of pollution can cause the water quality problem.
Oregon Department of Environmental Quality. Assessment Methodology for Oregon's 2004 Integrated Report on Water Quality Status. Retrieved March 22, 2006 from http://www.deq.state.or.us/wq/303dlist/docs/AssessmentMethodology2004.pdf
Oregon Department of Environmental Quality. Oregon Water Quality Index Summary Report, Water Years 1995-2004. Retrieved May 5, 2006 from http://www.deq.state.or.us/lab/wqm/docs/OWQISummary04.pdf