The Wilder Farm Water and River Quality (Exhibit C)

Part of the Minnesota River Decision Cases (other cases available)
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The Minnesota River:

The Minnesota River is one of the state’s most polluted waterways. In 1992 Governor Arne Carlson set a fishable, swimmable Minnesota River as a public policy goal. After extensive research, the Minnesota Pollution Control Agency (MPCA) decided that reducing suspended solids in the river by 40% was a necessary step toward achieving those ends.

The more than 350 miles of the Minnesota River drains over 17,000 square miles of watershed before emptying into the Mississippi River. Ninety-two percent of land use in the watershed is related to agricultural activity.

Water quality problems of the Minnesota River are particularly associated with sediment transport. It is interesting to note that the river may have naturally carried appreciable amounts of sediment prior to settlement. For example, early explorers occasionally described the river as looking as if "whitish clay had been dissolved in it" or that it was "a little whitish, without transparency in the water." The Native American word from which "Minnesota" is derived means "water the color of a cloudy sky." However, it is generally concluded that the river was cleaner prior to settlement and supported a more diverse biotic community.

The MPCA has concluded that the degraded conditions in the lower river stem from nonpoint source pollutants entering from upstream areas. Nonpoint source pollution comes from broad land areas rather than specific sources, such as factories or chemical tanks. Streams in the upper basin often lack permanently vegetated stream-side buffer zones. The U. S. Geological Survey estimates that the river at Mankato carries a sediment equal to a 10-ton dump truck load every five and one-half minutes.

Excess sediment damages the river by filling reservoirs and increasing water treatment costs. It affects the ecology of the river in a number of ways. The sediment itself blocks or absorbs light. This kills the plants that grow on the bottom of the river and raises the temperature of the water. Both of these effects can damage other aquatic life. When the sediment settles, it coats the river bottom and fills cracks and crevices. This eliminates habitat for many bottom-dwelling organisms and interferes with the spawning of fish. This condition is found throughout the Minnesota River and its tributaries.

Inorganic sediment from agricultural fields is usually associated with other materials, such as organic matter, phosphorus compounds, and nitrogen compounds, as well as some toxins. Much of this material has the effect of reducing oxygen levels near the bottom of the river, where fish and invertebrates live. Phosphorus and nitrogen, for example, are nutrients that allow free-floating algae to multiply profusely. When these algae die, bacteria and other decomposers draw heavily on the oxygen reserves of the river, effectively suffocating bottom-dwelling organisms. Excessive soil organic matter entering the river can also tie up oxygen. Oxygen levels, pollutants, and the various life forms in the river can all be studied to give researchers an idea of how severely a river or stream is impacted.

The Chippewa River:

The Chippewa River drains one of ten major watersheds that comprise the Minnesota River Basin. The environment of the Chippewa River has been altered significantly by government and private drainage projects over the past 40 years. Many areas were drained using open intake tiles so crops could be grown on the land.

Controversy surrounds the use of surface intake drainage as it relates to water quality in the river. Surface intakes are drains at or slightly above the surface of the field. They are placed in low areas where water ponds. In presettlement times, runoff water entering these depressions almost never made it to the river. Today, ponded waters, which are sometimes laden with suspended solids, can flow directly from agricultural fields into ditches and ultimately into the river through open intake drains. Increased flow in waterways during times of snow melt and heavy rainfall can also lead to stream bed and bank erosion.

The water quality of the Chippewa River has only been tested near where it joins the Minnesota River at Montevideo. Pollution levels there were high, based on low numbers and absence of certain invertebrates. Habitat quality of the Chippewa was well below average for the major Minnesota River tributaries. It should be noted that a flood control project of the Army Corps of Engineers sometimes routes water from the Minnesota River into the Chippewa upstream from Montevideo. Also, the city of Montevideo itself can contribute to pollution of the Chippewa.

A Natural Resource Conservation Service (NRCS) land use study partially answered the question of whether agricultural land use has a significant impact on the Minnesota River System. They studied ten minor watersheds in the Blue Earth, Le Sueur, and Watonwan watersheds. As is typical in the Minnesota River Basin at large, erosion levels in these watersheds were below five tons per acre per year, which is considered the tolerable level based on soil formation rates. Still, 38,000 tons of soil washed out of these watersheds into the river system yearly. This shows that even a small amount of pollution per acre multiplied by the millions of acres within the Minnesota River Basin can adversely affect water quality. This study also showed that significant reductions in sediment and nutrients could be achieved using existing technology for residue and tillage management. Models predicted that if one-sixth of the land was managed to retain 30 to 40% residue on the soil surface after planting, a 25% reduction in deliverable sediment could be achieved.

Information for this exhibit obtained from Minnesota River Assessment Project Report: Report to the Legislative Commission on Minnesota Resources. Volumes I, III, IV & the Executive Report. Published by the Minnesota Pollution Control Agency. 1994.

Part of the Minnesota River Decision Cases (other cases available)
View Decision Case or Teaching Note for this case.