Water Quality Monitoring

Select a location to view test results.



Safe Level

Total Suspended Solids (TSS)


90 MG/L

E Coli


126 mL



10 MG/L

What Am I Looking At? An Explanation of FBSR's Water Quality Monitoring Program

Friends of the Big Sioux River recognizes three primary contaminants that impair water quality: 1) total suspended solids (TSS) from soil erosion, 2) E Coli from animal waste, and 3) nitrates from fertilizer. During the summer months, we test for these three contaminants to determine that bodies of water meet the criteria for their designated uses (DUs). Graphs posted on our website depict safe levels (a red line) and test levels (blue line). The safe levels have been assigned by the South Dakota DENR. The sites selected by FBSR are common points of recreation and have DUs of swimming and limited contact recreation. If test results reveal contaminant levels that exceed established safe levels, they are not safe for their DUs, including swimming and limited contact recreation. We are providing you with this water quality data so you can make safe, informed decisions about your summer recreation.

Water Quality FAQs

What are Total Suspended Solids (TSS)?

TSS is the dry-weight of suspended particles, that are not dissolved, in a sample of water that can be trapped by a filter that is analyzed using a filtration apparatus. TSS can include a wide variety of material, such as silt, decaying plant and animal matter, industrial wastes, and sewage. High TSS levels decrease water clarity and can interfere with water chemistry and photosynthesis processes. For bodies of water designated for immersion recreation, 158 MG/L is the established safe level.

What is E Coli?

E Coli is a bacterium commonly found in the intestines of humans and other animals, where it usually causes no harm. Some strains can lead to illness, especially in old people and children. The presence of fecal coliform bacteria in aquatic environments indicates that the water has been contaminated with the fecal material of man or other animals. Common sources of E Coli include wastewater treatment plants, failing septic systems, domestic and wild animal waste, and storm water runoff. For bodies of water designated for immersion recreation, 126 CFUs is the established safe level.

What are nitrates?

Nitrates are a salt or ester of nitric acid, containing the anion NO3 or the group —NO3. Nitrates are an essential source of nitrogen for plants and are commonly used in fertilizers. When nitrogen fertilizers are used to enhance soil fertility, nitrates may be carried by rain over or through the soil and deposited in surface water. High levels of nitrates in drinking water can lead to Blue Baby Syndrome. The national safety level has been established at 10 MG/L. South Dakota standards have been set at 50 MG/L.

What is designated use?

Designated use is state or tribe specified appropriate use(s) for water determined by the fitness of physical/chemical/biological characteristics, geographical settings, scenic qualities, and economic considerations. Bodies of water can be designated as “fishable/swimmable,” and must undergo inspection every 3 years to determine if the standard has changed. Designated uses include protection of aquatic life, recreation, drinking water, and agricultural/industrial purposes. The State of South Dakota identifies the Big Sioux River’s designated uses as domestic water supply, warm water semi-permanent fish life, warm water marginal fish life, immersion recreation, limited contact recreation, fish and wildlife propagation, and irrigation.       

How are water quality standards established?

Water quality standards are established by an analysis of 1) designated use, 2) water quality criteria, 3) antidegradation policy, and 4) general policies. Designated use establishes what the water can safely be used for. Water quality criteria is A numeric value of toxicity derived from 1) narrative criterion which limits toxicity of waste discharge, 2) biological criterion which describes the number and type of aquatic species in the water, 3) nutrient criterion which establishes how much nutrients can be in the water, and 4) sediment criterion which enumerates the amount of contaminated and uncontaminated sediment in the water. An antidegradation policy is a 3-tier policy geared to 1) maintain current water uses, 2) support fishable/swimmable uses, and 3) protect waters with the greatest ecological significance. Finally, general policies provide states and tribes, with approval to establish mixing zones (where sewage is discharged and diluted), variance (temporary relaxation of water standards), and low-flow (regulating water scarcity).

Why are excess nitrates in the water a problem?

High nutrient levels in lakes and rivers can lead to eutrophication, which allows algae to thrive. Algal blooms can pose a threat to human health, as well as emitting a strong, pungent odor. Furthermore, excessive algae can absorb all the oxygen available in a body of water, effectively suffocating fish and other aquatic life. Hypoxic water areas are more popularly known as “dead zones.” In the Gulf of Mexico, runoff from the Midwest farming states has created a 6,000-7,000 square mile dead zone. Other examples can be seen in the Chesapeake Bay, Great Lakes, and Cape Perpetua.