WHAT IS RUNOFF?
Runoff is the part of precipitation that reaches streams and rivers by flowing over or through the ground. It includes all the flow that passes a specific location on the river. Monitoring season runoff is calculated by dividing the total flow volume by the total number of contributing acres. This is equivalent to redistributing the flow out equally over the watershed, then measuring that depth in inches.

WHAT ARE NITRATES?
Nitrogen exists in the environment in many forms. In recent decades, there has been a substantial increase in nitrogen fertilizer use. Nitrogen can affect drinking water. Elevated nitrate-nitrogen in the Minnesota River can pollute aquifers it recharges. At high enough concentrations, nitrate-nitrogen can cause infants who drink the water to become sick (methemoglobinemia). Downstream, nitrate-nitrogen from the Minnesota River contributes to hypoxia (low levels of dissolved oxygen) in the Gulf of Mexico by stimulating the growth of algae which, through death and decay, consume large amounts of dissolved oxygen and thereby threaten aquatic life.

WHAT IS PHOSPHORUS?
Phosphorus is an important nutrient for plant growth. Point-source phosphorus comes mainly from municipal and industrial discharges to surface waters. Nonpoint-source phosphorus comes from agricultural fields, urban runoff, construction sites, feedlots, and septic systems. Most point-source phosphorus is dissolved, whereas most nonpoint-source phosphorus is sediment-attached.
Elevated levels of phosphorus stimulate the growth of algae. The death and decay of algae can deplete the supply of oxygen in the river. Excessive algae growth, death, and decay can severely deplete oxygen supply, endangering fish and other kinds of aquatic life. Low dissolved oxygen rates are particularly a concern during low flow times or in slow-flowing areas such as reservoirs and the lower reaches of the Minnesota River.

WHAT ARE TOTAL SUSPENDED SOLIDS?
The transport of sediment is a natural function of rivers. Modification of the landscape has accelerated the rate of erosion of soil into waterways. Elevated sediment (suspended soil particles) has many impacts. It makes rivers look muddy, affecting aesthetics and swimming. Sediment carries nutrients, pesticides, and other chemicals into the river that may impact fish and wildlife species. Sedimentation can restrict the areas where fish spawn, limit biological diversity, and keep river water cloudy, reducing the potential for the growth of healthy aquatic plants.

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This page was last updated 12/12/02
Minnesota River Basin Data Center | Minnesota State University, Mankato
184 Trafton Science Center S, Mankato, MN 56001 | Phone: (507)389-5492 | FAX: (507)389-5493 | Email: mrbdc@mnsu.edu