Frequently asked questions about lakes

The control or removal of emergent aquatic vegetation, such as cattails, bulrushes or wild rice, does require a DNR aquatic plant management permit). The DNR Section of Fisheries regulates the control or removal of aquatic vegetation by physical or chemical means. Permits can be applied for through the DNR Regional Fisheries Office serving the area where your shoreline property is located. They may be contacted at (651) 259-5100 for more information.

Also see the DNR Waters information sheet titled Shoreline Alterations: Lakescaping (1.1 Mb).

The term "environmental lake" most likely is taken from the Natural Environment lake classification found in Minnesota's Shoreland Management Program. Many people mistakenly infer that the Natural Environment classification on many of Minnesota's smaller, shallow lakes means they are wild lakes with limits on motors, hunting or fishing. To a degree, this is true in that Natural Environment is the strictest of the three lake classifications. However, the classification is used to determine lot size, setbacks and, to a certain degree, land uses on the adjacent land. The classification has nothing to do with surface water use of boats or motors, hunting and fishing or fish management. These are governed by other regulations. As the larger, deeper lakes that are more suitable for recreational or general development (the other two lake classifications) become developed, there is growing pressure to develop the smaller, more sensitive natural environment basins. Hence there is no guarantee that the wilderness character that some of these lakes now have will be preserved. It is a growing concern of many local governments, outdoors recreation groups and the DNR that such lakes may require more protection than currently provided in the rules.

The shoreland management rules were established in the early 1970's and are intended to help govern the orderly development of land adjacent to Minnesota's many lakes and rivers. The way it works is that DNR established statewide standards and lake/river classifications that local governmental units (counties and municipalities) were then required to incorporate into their land use controls (planning and zoning ordinances).

A lake is not defined by size or depth as some may suggest. A lake may be defined as an enclosed basin filled or partly filled with water. A lake may have an inlet and/or an outlet stream, or it may be completely enclosed (landlocked). Generally, a lake is an area of open, relatively deep water that is large enough to produce a wave-swept shore. For regulatory purposes, Minnesota has grouped its waters into two categories: public waters and public water wetlands. This makes it easier to determine whether a DNR public waters work permit is required before changes can be made to the course, current, or cross section of these waters.

The state has an interest in protecting not only the amount of water contained in these lakes, wetlands and streams but also the container that confines these waters (i.e., lakes, wetlands, and streams). The obvious reason for these conservation measures is that these waters provide a vital habitat for fish and wildlife, as well as a place for people to fish, hunt, trap, boat, and swim. However, the most important benefits provided by these waters are less obvious:

• Substantial amounts of water are stored in these areas and it can seep into the ground to recharge ground water aquifers.
• Lakes, wetlands, and streams can store excess water in times of flooding and provide an important reserve of surface water during times of drought. These areas are nature's water treatment systems. They provide an ideal environment for aquatic vegetation and animal organisms to purify the water we have contaminated with suspended soil (erosion), nutrients (from fertilizers and animal wastes), and other pollutants.

Naming a lake in Minnesota, or changing the name, is guided by Minnesota Statue 83A.04 - 83A.07.

The process begins at the county where the lake is located. Fifteen or more voters registered in that county must petition the county board of commissioners for a public hearing. If the county board agrees on the proposed name, the board adopts a resolution in support of the name.

The resolution is forwarded to the Department of Natural Resources Commissioner for approval. The Commissioner will not approve a name that commemorates or may be seen to commemorate, a living person.

Approved names are submitted to the U.S. Board on Geographic Names for federal approval and use.

Also see: Naming Geographic Features

To varying degrees many, if not most lakes receive some water from ground water sources or are "spring fed." When swimming, one might notice colder, localized areas or areas of the lake might remain open along the shoreline during winter. Both are likely due to ground water flowing into the lake. Lakes also lose water to ground water sources. Most lakes have both; some ground water flows into the lake and some lake water flows into the ground water system or aquifer. Variations in precipitation patterns can cause the amount in or out to change significantly. Generally, complex hydrologic computer models including information such as watershed, geology, precipitation, lake level, and ground water level data are used to estimate how much is flowing in or out of the lake.

A meandered lake is a body of water, except streams, located within the meander lines shown on plats made by the United States General Land Office (Federal Bureau of Land Management). A meander line is a series of courses and distances to delineate the area of a body of water. It is not a boundary line, nor does it convey land ownership information.

(See complete legal definition under Public Waters Work Permits Program.) Public waters are all water basins and watercourses that meet the criteria set forth in Minnesota Statutes, Section 103G.005, Subdivision 15 and are designated on the DNR's Public Waters Inventory Maps.

The ordinary high water level (OHWL) is a reference point that defines the DNR's regulatory authority over development projects that are proposed to alter the course, current, or cross section of public waters and public waters wetlands. For lakes and wetlands, the OHW is the highest water level that has been maintained for a sufficient period of time to leave evidence upon the landscape. The OHWL is commonly that point where the natural vegetation changes from predominately aquatic to predominantly terrestrial. For watercourses, the OHWL is the elevation of the top of the bank of the channel. For reservoirs and flowages, the OHWL is the operating elevation of the normal summer pool. The OHWL is also used by local units of government as a reference point from which to determine structure setbacks from water bodies and watercourses. See also legal definition under Hydrographics Program.

Also see technical paper (TP #11) "Guidelines for Ordinary High Water Level (OHWL) Determinations". This paper reflects current terminology as well as the DNR Area Hydrologists' addresses and phone numbers.

The DNR does not control the water level elevation of lakes. In general, the water level of a lake is entirely dependent upon the amount of snowfall and precipitation that an area receives, how much of the resultant moisture is contributed by runoff into the lake, how much water is recharged to or discharged from the lake through ground water and how much water evaporates from the lake. In some instances, the water level is controlled by illegal human activity or beaver activity. See also the DNR Lake Level Minnesota Program, for information about lake gage measurements and lake levels.

• The key to this question is how water density varies with water temperature. Water is most dense (heaviest) at 39º F (4º C) and as temperature increases or decreases from 39º F, it becomes increasingly less dense (lighter). In summer and winter, lakes are maintained by climate in what is called a stratified condition. Less dense water is at the surface and more dense water is near the bottom.
• During late summer and autumn, air temperatures cool the surface water causing its density to increase. The heavier water sinks, forcing the lighter, less dense water to the surface. This continues until the water temperature at all depths reaches approximately 39º F. Because there is very little difference in density at this stage, the waters are easily mixed by the wind. The sinking action and mixing of the water by the wind results in the exchange of surface and bottom waters which is called "turnover."
• During spring, the process reverses itself. This time ice melts, and surface waters warm and sink until the water temperature at all depths reaches approximately 39º F. The sinking combined with wind mixing causes spring "turnover."
• This describes the general principle; however, other factors (including climate and lake depth variations) can cause certain lakes to act differently.

Two general methods are available to prevent your lakeshore from eroding: hard armoring and soft armoring. The most common hard-armor technique is riprap, which consists of placing large rocks in the water and up the slope of the eroding shoreline. Riprap is commonly used to control erosion along streambanks and lakeshores where vegetation is not sufficient to prevent erosion caused by high water or wave action. It is expensive to install and is often installed incorrectly. If installed properly, however, riprap normally provides good protection from the impact of waves and ice. Some believe that riprap is overused and unsightly and that Minnesota lakes have lost much of their natural shoreline to riprap.

In contrast to hard-armor techniques, soft-armor methods use organic and inorganic materials combined with plants to create a living barrier of protection. Bioengineering, a soft-armor method, provides erosion control through the use of live vegetation. Bioengineering can be used in addition to or in place of hard armor such as rock riprap. It creates a more natural, environmentally friendly shoreline that includes additional benefits to erosion control, such as habitat enhancement. An excellent source of information on these methods is the DNR publication "Lakescaping For Wildlife and Water Quality". A DNR public waters work permit may be required for both soft and hard armoring methods.

Also see: Shoreline Alteration Information Sheets

See advice on preventing swimmer's itch from the DNR Fish and Wildlife Division, or contact the Minnesota Department of Health, Acute Disease Epidemiology, at 612-676-5414. For information on how to treat swimmers itch, contact your doctor.

A Lake Improvement District (LID) is special-purpose district formed around a lake in accordance with Minnesota Statutes, sections 103B.501-103B.581 . A lake improvement district is a local unit of government established by resolution of appropriate county boards and/or city governing bodies, or by the commissioner, for the implementation of defined lake management projects and for the assessment of the costs thereof.

Printouts of lake survey reports, depth maps, and fish consumption advisories are available from the DNR Lakefinder.

See the water permits page to learn when you need a permit.

Read the article Pardon Me Myth! Who Owns the Lake Bed? by Dave Milles.