The telephone rings at the local Wisconsin Department of Natural Resources (WDNR) Service Center. On the line is a lake shore property owner from northern Wisconsin. “My water has been low for so long that I have a bunch of grasses and tall weeds growing in what used to be the lake bottom. I also have trash and old tree branches that would be easy to get out now. What can I do? Can I cut the brush with my weed whacker? Can I drag out those old tree branches?”

Avoid Removing Vegetation

These sorts of questions are common during dry times…so what can you do? In general, it is best to avoid removing vegetation and disturbing the exposed lake bed during low water times. Droughts are a natural occurrence and northern Wisconsin lakes have experienced periods of declining water levels in the past. In fact, these water level fluctuations are important for a lake’s health, particularly in the near-shore zone. Shorelines and shallow areas of lakes play a vital role in providing habitat for fish and wildlife and for protecting water quality. A diverse native plant community provides the best habitat and defends against the establishment of invasive species. Until water levels return to normal, it is important for lake property owners to avoid inadvertently harming exposed lakeshore areas. Minimizing your impact is critical to protecting this fragile ecosystem.

Know the Rules

There are some activities, during low water periods, that may be necessary to maintain access, reduce nuisance accumulations of biological material, and control invasive species like reed canary grass, purple loosestrife, or even spotted knapweed. However, removing threatened or endangered plant species is against the law and can result in fines. Most activities conducted on the exposed lake bed, including beach grooming, cutting or chemically treating plants, are regulated by the WDNR; for more information go to http://www.dnr.state.wi.us/lakes/commonquestions. Keep in mind that each county has a shoreland protection ordinance that limits the amount of clearing that can be done on land within 35 feet of navigable waterways (the shoreland buffer). Check with your local county zoning administrator for details (http://dnr.wi.gov/org/water/wm/dsfm/shore/county.htm).

Impacts on Critters and Plants

A lake’s outline, where land and water meet (the near-shore habitat), combined with the littoral zone, that area of a lake where light can penetrate down to grow aquatic plants (often less than 15 feet in depth), are incredibly important to wildlife and plants. The littoral zone harbors and supports key elements of the lake food chain, sustaining the productivity of the lake and the critters and plants living within the aquatic system.

The extent and quality of wetlands adjacent to a water body can also influence the impacts low water levels might have on lake habitat. During lower water levels, fringe wetlands along a lake’s edge may decline in productivity.

Other factors impacting fish and wildlife habitat on the lake include the type of lake bottom and aquatic invertebrate community. Cobble lake bottoms that are important to fish reproduction may be high and dry, narrowing the amount of spawning habitat available on a lake. Invertebrates relying on submersed wood and emergent plant stems may find fewer habitats available to them in the near-shore area. Some invertebrates, like dragonflies and mayflies, are mobile and can move to deeper habitat, but those that cannot shift will be in trouble.

What Do the Experts Say?

Susan Knight, an aquatic biologist with the WDNR and the UW-Madison Trout Lake Station, describes the short-term effects of declining water levels. “Beaches are exposed. Wood is left high and dry. Some plant growth occurs on the exposed shore, as the lake is shallower,” she says. “Light can reach further into the lake, which sets a depth for plant growth closer to the center of the lake, giving plants an opportunity to grow in different areas.” But what does this mean for the lake? Knight describes several characteristics of a lake that play into how declining water levels might impact habitat. “Lake shape (that is its depth and contours), as well as the lake’s hydrology and trophic status, affect how habitat is influenced by lower water levels,” says Knight. For example, shallow seepage lakes (lakes that do not have an inlet or outlet where the main water sources are groundwater and precipitation) can be especially vulnerable, and declining water levels could lead to less diversity and cause a decline in ecosystem productivity. “Plants in deeper, nutrient rich lakes can keep up with declining water levels easier than small, slow-growing vegetation typically found in shallow lakes with fewer nutrients, where the plant life disperses slowly over time,” explains Knight.

According to Knight, several studies have found that modest water level fluctuations can lead to increased plant diversity. However, large fluctuations, especially from one growing season to the next, may lead to lower species richness, fewer rare plants and more invasives on the shoreline.

Frank Koshere, WDNR’s aquatic plant coordinator in Superior, shares some tips for people concerned about maintaining their lake health in low water times. “Understand the type of lake you live on—learn about its water inputs and watershed characteristics. Be careful in your use of the lake, especially along the shoreline, both on land and in the water,” says Koshere.

Shifting boater behavior by getting lake users to go into deeper water away from near-shore areas and shallow water is another strategy to employ. “Having lake users follow slow no-wake zone rules during low water levels is more important now than ever before,” he says.

Pamela Toshner, a WDNR lake coordinator in the northern region, suggests lake organizations work with their local resource professionals to identify and protect critical habitats and fragile areas on their lake through sound lake management planning activities. “Grant funding is available to help lake groups do this kind of assessment; knowing where these areas are on your lake can make a difference when trying to protect your lake in low water times,” says Toshner. “Reducing nutrient inputs from the watershed to your lake is another key step in lessening the negative impacts declining water levels can have on a lake,” she states. Water quality enhancement activities like preserving shoreland buffers, installing rain gardens, initiating sound agricultural practices, adhering to construction site “best management practices,” annual septic maintenance, and proper lawn care can help alleviate nutrient and sediment inputs from the watershed that are worsened when water levels decline.

Low Water Has Benefits

Periodic low water conditions can be beneficial for lake ecosystems. Sediments can consolidate and allow new plants to colonize the lakebed and provide habitat for rare plants and shorebirds. In fact, the growth of Fassett’s locoweed (Oxytropis campestris), one of our most rare shoreline plants, is dependent upon periodic fluctuations of water levels. This plant is only found in a handful of lakes on the planet (all in Wisconsin), and each of these lakes is subject to a wide fluctuation in water levels. A population recently reemerged on a northern Wisconsin lake after no sightings since 1934 (read more about this plant at www.uwsp.edu/cnr/uwexlakes).

When water levels return to normal, an expansion of new plants becomes habitat for fish and wildlife, removes nutrients from the water, and can increase water clarity. However, human actions that cause water levels to drop farther than this natural variation, or prevent the lake from returning to normal conditions, may harm the lake and its inhabitants over the long-term.

More On Low Water

For more information on this topic check out the flyer “You Don’t Know What You’ve Got ’Til It’s Gone” on the UWEX Lakes web site at www.uwsp.edu/cnr/uwexlakes/ecology, or go to the Wisconsin Association of Lakes (WAL) web site for information from a May 2009 seminar focusing on this issue (www.wisconsinlakes.org/events/09may_lowlake.html).

Other links to check out include:
Wisconsin State Climatology Office - www.aos.wisc.edu/~sco/

Wisconsin Initiative on Climate Change Impacts - www.wicci.wisc.edu/

USGS Water Watch - http://waterwatch.usgs.gov

U.S. Drought - www.drought.unl.edu/dm/monitor.html

Permit Required?

Some minor vegetation management (except for wild rice) and other activities done by hand do not require permits from the WDNR. The following activities require a permit: cutting plants in an area larger than 30-feet wide, driving a motor vehicle on the lakebed, tilling, and chemically treating vegetation if the area is wet. These permits are designed to assure that the activity does not damage the lake or the sensitive exposed habitat.

If you want to groom or disk the exposed lakebed area (e.g. beach, vegetation, etc.) on your property along a navigable waterway, a permit is required. This includes grooming or disking in areas of the beds of waterways that are currently exposed because of low water levels. Certain grooming or raking with handheld devices may qualify for an exemption. A permit is required to disturb, remove or redistribute material from the bed of a navigable waterway. Removal of bottom material with handheld devices may qualify for an exemption by following specific standards.

If you want to cut or mow emergent vegetation that is growing on your exposed lakebed using motorized equipment (e.g. riding lawn mowers, tractors, ATVs, etc.), you need to apply for a permit. If you will be cutting or mowing the vegetation by hand (e.g. push lawn mower, clippers, etc.), a permit is only required if you remove native vegetation in an area that exceeds a single 30-foot wide path per property, measured along the shoreline. You also need a permit if you are removing state or federally listed threatened or endangered plant species. The following non-native invasive species may be removed by hand in an unlimited area without a permit: phragmites, Eurasian water milfoil, curly-leaf pondweed, and purple loosestrife.

On lakes with connecting streams, dams or other water level control structures, modifications may be considered to temporarily raise or lower the water level due to extreme conditions. However, permanent changes in water levels have significant implications for downstream property owners and users. Project review can be lengthy and locally controversial. Establishing or changing water levels on lakes or flowages will generally require WDNR approval.

Lakes without natural outlets are even more difficult to address. Pumping water into a seepage lake can be expensive and results in very little change in the water level, as most of the water is basically recycled back to the local groundwater system.

For more information see http://dnr.wi.gov/org/water/fhp/waterway/lakelevels.html.