Water Quality Fact Sheets
Sediment 

Parameter: Sediment                         Abbreviation: SED
Classification: Nutrient                       Surface or Ground Water? Surface Water
EPA Priority Pollutant? Yes                 Is it Carcinogenic? No
How is it Measured? tons per year (ton/yr)
Illinois EPA General Use Standard: No Standard

What you should know about Sediment:

bullet Sediment is the coarser grained particles that are washed off the land surface into the stream. Sediment can be rock, gravel, sand, clay, or silt. Smaller particles like clay and silt are usually suspended in the water column (See Suspended Sediment), but a portion of the total clays and silts washing into our streams comes out of suspension and settles out onto the channel bed during periods of low flow and in slack water areas (pools & behind dams)
bullet Sediment moves down the river system in pulses, which coincide with the increase in stream flow associated with high flow events (spring thaw, summer thunderstorms, etc.). During low flows, the sediment settles out and covers the gravel/rock bed of river.

Major Sources of Sediment:

bullet Construction sites for urban developments can be major sources of silty sediment.
bullet Streambank erosion is another source of sediment. Excessive erosion occurs along a stream channel where the stream is cannot withstand the forces associated with urban runoff following storms.
bullet Improperly maintained agricultural fields (like those with no stream buffer).

Minor Sources of Sediment:

bullet When aquatic/terrestrial organisms die, their detrial remains break down into smaller and smaller particles that collect in the slack water areas of our rivers and streams, whether a quiet, natural pool of a small stream, or the large impoundment created by a manmade dam.

Typical Concentration for the Fox River Watershed:

bullet Total Suspended Solids: less than 50 mg/L in the upper watershed and 50-100 mg/L in the lower watershed.

Impacts to Ecosystem:

  • When sediment settles out, it covers the highly valued aquatic habitat (like gravel and sand beds) and harms the aquatic organisms that form the foundation of the aquatic food chain (macroinvertabrates). It also covers habitat need by mussels, as well as spawning habitat used by game fish.

Impacts to Drinking Water:

  • Sediment in rivers where drinking water is taken from can clog water intake structures, increasing costs for routine maintenance and dredging.

Impacts to Recreation:

  • Deep water areas of streams and rivers are filled in with sediment, which degrades fishing and poses navigational hazards to boaters.

References

bullet IEPA, Illinois Water Quality Report 2000, April 2000.
bullet IEPA, Baseline Loadings of Nitrogen, Sediment, and Sediments from Illinois Watersheds, Nov. 1999.

 
Sediment Fact Sheet in printable, pdf file