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Water resource issues in the Red Cedar River Basin are often related to the associated land uses on the landscape. As previously mentioned, the primary land uses in the basin are agriculture and forestry. Agricultural croplands take up a significant amount of the land area and contribute a large proportion of the total phosphorus load to lakes and rivers in the basin. Although the majority of land in the basin is foreste, it accounts for a relatively small proportion of the total phosphorus load. The remaining land in the basin includes urban areas and pastures which account for the remaining phosphorus load. At the receiving end of the 2,000 square mile river basin are Tainter Lake and Lake Menomin.
Due to large phosphorus and sediment loads from the watershed, lakes such as Tainter Lake and Lake Menomin experience severe algae blooms and poor water clarity during most of the summer. Phosphorus is a primary nutrient essential for healthy plant and algae growth. However, large amounts of phosphorus in surface waters will result in excessive aquatic plant and algae growth.
In some streams, like the Red Cedar River, large amounts of phosphorus and nitrogen result in heavy aquatic plant growth, which can restrict recreational use and cause lowered dissolved oxygen levels at night. During the day, when plants are photosynthesizing, they produce oxygen, which is essential to aquatic life. However, at night, plants respire and use up oxygen. This lowering of dissolved oxygen levels can be detrimental to fish and other aquatic life.
What is known about pollutant loads in the basin
The Red Cedar River Basin has been studied extensively over the past decade to better understand the sources of nutrient loads and sediments to the river. Point sources, including discharges from municipal and industrial wastewater treatment plants, were found to contribute about 10% of the annual phosphorus load to Tainter Lake. Non-point sources, including cropland and barnyard runoff, construction site and streambank erosion and failing septic systems, contribute about 90% of the annual load. Nutrient levels within the basin appear to have been highest from 1965 to 1980. In the early 1980's the levels went down, but have since begun to increase. Increased poultry production, row crop farming, and residential growth have all led to increased nutrient runoff.
A few other water quality concerns in the Red Cedar River Basin streams include streambank erosion, sedimentation of riffle and pool areas, organic and nutrient loading from animal waste and elevated stream temperatures. The primary cause of streambank erosion is a combination of occasional flooding and excessive cattle grazing of streambanks in some areas. A frequent result of streambank erosion is sedimentation of pools, filling-in of spawning substrate in riffle areas and elimination of bank cover. Filling-in of spawning substrate in riffle areas impairs reproductive success of trout by reducing inter-gravel flow, which is necessary to maintain suitable temperature and oxygen conditions for eggs and larval fish. Sedimentation of riffle areas also destroys habitat for aquatic insects and other fish food organisms. Filling-in of pools reduces the amount of available cover for juvenile and adult fish.
Several of the watershed streams have summer water temperatures that are above optimal for coldwater fish like trout. Elevated water temperatures may result from a number of factors including lack of stream shading, reduced spring flow and poor habitat. The elimination of streambank vegetation reduces shading and increases solar radiation, resulting in increased stream temperatures. Streambank erosion and sedimentation of the stream bottom results in wider, shallower streams that may cause increased water temperatures. Impoundments (built by humans or beaver) on streams or spring areas also increase downstream water temperatures. The cumulative effect of these impacts may decrease the suitability of a stream to support a coldwater fishery.
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