From Little Cottonwood Restoration Project Report (link)
Hydrology
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Under certain conditions, recent changes in drainage (mainly ditching and tiling) in the upper portion of the watershed have resulted in water leaving the upper portion of the watershed at a faster rate.
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Wetland restoration, retention basins and/or culvert downsizing may be important Best Management Practices (BMP) for controlling peak water flows downstream.
Sediment
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Sediment concentrations (measured in parts per million) and sediment loads (measured in pounds or kilograms) were elevated at all four monitoring sites during runoff conditions.
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Most of the sediment load is delivered between Monitoring Sites #3 and #4. In 1999, sediment increased from 58 pounds/acre at Monitoring Site #3 to 710 pounds/acre at Monitoring Site #4.
Phosphorus
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Phosphorus concentrations and loads were moderate for the entire watershed.
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Sediments and phosphorus are directly correlated. The majority of the total phosphorus and soluble phosphorus are derived from runoff during storms.
Nitrates
- Based on samples taken during storms, much of the nitrate is reaching the river through leaching into shallow subsurface pathways. These pathways are mainly through underground public and private tile systems.
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Nitrates concentrations are usually elevated in much of the watershed up until the end of July. After July, leaching and runoff is minimized because of high evaporation rates during this part of the season. Highest nitrate loads and concentrations occur near the headwaters.
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Nitrate levels decrease near the middle of the watershed due to wetland processes. Levels increase again after Monitoring Site #3.
Pathogens
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Most of the elevated fecal coliform bacteria counts occur during runoff events, suggesting feedlots as the sources of bacteria. High counts during low flow conditions occurred at times during the study, suggesting failing septic systems as that main point source.
- The highest geometric means (monthly averages calculated from five samples) were found at Monitoring Site #3. Possible reasons include the high number of livestock facilities, some of which allow the animals access to the river.
