FAQ

How does my front yard influence water quality?

The water cycle is a long journey! After a rain or snow event, the water in your yard has two options: 1) flow into a storm drain or 2) soak into the ground. With option one, water flows off hard surfaces, such as driveways and parking lots, and runs into storm drains. Any residue on these surfaces is carried into the drain and deposited unfiltered in the river. With option two, rainwater or snowmelt leaches through the soil and eventually reaches an aquifer, a layer of permeable rock that contains the groundwater. Flowing through capillaries, the groundwater eventually reaches a surface water source and is discharged. If you live in the Big Sioux River watershed, your groundwater discharges in the Big Sioux River or one of its tributaries.

What is nonpoint source pollution?

Nonpoint source pollution is a result of multiple, diffuse sources of pollution contributing to a larger pollution problem. Examples include parking lots, lawns, and crop fields. These surfaces are spread out across hundreds and thousands of square miles and are individually not huge polluters. However, after rainfall events, runoff contaminated with oil, brake fluid, fertilizer, and pesticides converge in a river and constitute a large pollution problem.

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.           

What is total maximum daily load (TMDL)?

The total maximum daily load is the maximum amount of pollution a body of water can receive while still meeting water quality standards. TMDL is determined by adding the Waste Load Allocation (the existing/future pollution level) to the Load Allocation (estimated background pollution) added to the Margin of Safety (calculated uncertainty in meeting water quality standards). Evaluation of body of water’s TMDL includes analyzing watershed characterization, impairment status, data gaps and monitoring report, source assessment, load allocation, set targets, and implementation plans. The evaluation of TMDLs allow states to identify impaired bodies of water

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).

What is the Clean Water Act?

Originally titled the Federal Water Pollution Control Act, this law was first enacted in 1948, completely rewritten in 1972, and additionally amended by the Clean Water Act of 1977 and the Water Quality Act of 1987. The CWA is the primary federal law governing water pollution with the objective of restoring and maintaining chemical, physical, and biological integrity of US waters. The law targets point source and nonpoint source pollution, manages wastewater treatment, and protects wetlands. More information is available on the EPA website. 

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.