Main

October 23, 2007

Lake Restoration - Introduction

falllake.jpg Healthy lakes ecosystems are critical to maintain as they harbor an abundance of plant and animal life. The daily choices Minnesotans make, be it lawn maintenance, car washing, or actively getting involved with lake protection and restoration are dramatic impacts on the lake ecosystem.
This website outlines some basic aspects of the lake ecosystem and procedures people can take which help prevent the deterioration of the lake ecosystem. Our goal is to better inform people as to some of the strategies to restore lakeshore property.

The Lake Ecosystem

Every lake sits in the middle of its watershed, the area of land that drains runoff into the lake. The organisms of the lake ecosystem consist of a complex variety of aquatic vegetation and upland plant species, as well as all animals that live in the lake or make frequent contact with the lake. Maintaining a variety of vegetation is absolutely critical to the health of the lake and everything living around the lake.

Lake Plants
Phytoplankton (diatoms, green algae, and blue-green algae) is the smallest group of lake organisms. All other life of the lake ecosystem depends on a balanced level of phytoplankton. Algae capture the sun’s energy and chemically combines water and carbon dioxcide to produce oxygen; this process is called photosynthesis. Microscopic invertebrate organisms such as copepods and fairy shrimp called zooplankton eat algae which transfers nutrients and energy though the food chain. In short, phytoplankton and zooplankton allow a lake ecosystem to exist.

Shoreline vegetation is also essential to the wellbeing of a lake’s ecosystem. Shoreline vegetation reduces wave intensity which prevents soil erosion and sedimentation, allows for protection of young fishes and other animals, and reduces the amount of nutrients entering the lake. In short, shoreline vegetation keeps a lake ecosystem healthy.

Lakeshore vegetation
Submergent and Emergent plants produce oxygen, provide underwater cover for fish amphibians birds and insects, create surfaces for algae to adhere to, break the energy of waves which prevents erosion, and stabilize bottom sediments which would otherwise be resuspended. These plants also break down nutrients, such as phosphorous, before they are able to entire surface water.
Shoreline and Upland Plants have extensive root systems which stabilize soils against pounding waves and hold soil in place to prevent soil erosion. This is important because soil erosion causes excessive nutrients to enter surface water and causes sedimentation which is discussed in the problems page.

Problems


Phosphorous: Important and Detrimental to the Lake Ecosystem

What is Phosphorous?
Phosphorous, a compound common in the lake ecosystem, can be derived from natural organic sources such as animal manures, composts, fallen tree leaves, grass clippings, rainfall, soil and airborne dust. Phosphorous is essential to plant growth and fertility. However, increased amounts of phosphorous entering surface waters can create excessive algae growth which creates problems such as decreased water quality, fowl odor, habitat loss, and fish kills. The problems caused by excessive phosphorous are not only detrimental to the lake ecosystem, but extend to decreased lakeshore property values!

How do excessive amounts of phosphorous accumulate in lakes?

Humans increase the amount of phosphorous entering a lake in two ways, through point sources and non-point sources. Point sources of water pollution are caused by factories and wastewater treatment plants. Non-point sources, commonly known as runoff pollution or stormwater pollution, occurs when rain and melting snow push phosphorus, as well as other nutrients, from the landscape into the lake. Even if one does not live by a lake runoff pollution directly affects the lake ecosystem. Why? Because the waste enters the lakes watershed, the surrounding land area that drains into a lake. Whether it be via natural drainage system or an artificial drainage system the nutrients from our own back yards will wash into the lake.

What damage does excessive phosphorous cause?
High phosphorous levels create “algal blooms,? a floating, green, slimy cover on the lakes surface. The frequency and severity of algal blooms increase along with the lake’s phosphorous concentration. Algae growth can be severe enough that it blocks the sun from penetrating the surface of the lake. This is especially detrimental to the lake’s ecosystem because fewer aquatic plants will be able to produce oxygen through photosynthesis. And when the algae die, the oxygen they produce will be consumed in the decomposition process which robs fish and other aquatic life of this essential element. The loss of oxygen causes the loss of aquatic life which greatly upsets the entire lake food web. And, of course, excessive phosphorous will also decrease the monetary and aesthetic value of lakeshore property.

Problematic landscapes
Urban watersheds: Runoff pollution is especially prevalent in urban watersheds where there is more impervious area; melting snow and rainwater easily carry nutrients to the lake because hard surfaces such as streets, driveways, and rooftops do not allow for absorption. Runoff is swiftly carried to storm sewers and often enter the lake directly.
Lakeshore Bluegrass lawns without “weeds?: Bluegrass lawns extending to the edge of the waterfront without any native grasses or plants is especially dangerous to the wellbeing of the lake ecosystem. The European Bluegrass has very shallow roots and do not absorb and filter nutrients like native grasses do. Bluegrass lawns do not have a chance to protect the lake by reducing runoff in the absorption of nutrients such as phosphorous before entering the lake. Exposed soils on construction sites and steep slopes are also problematic surfaces in dealing with runoff.

HEY! One pound of phosphorous can produce up to 500 lbs. of algal growth once it washes into a lake!

Shoreline Erosion and Sedimentation

One of the main problems experienced by lakes is shoreline erosion. Shoreline erosion is caused by waves pounding against and destroying shoreline vegetation. Waves can be caused both naturally and by recreational use of waters such as boating and jet-skiing. Shoreline erosion is usually minimal in natural lake habitats with prolific growth of submergent and emergent vegetation. The fallacy that submergent plants are simply “weeds? endangers the wellbeing of the lake ecosystem when lakeshore owners remove these essential organisms. Removing aquatic plants from the shoreline aggravates soil erosion causing the water transparency to be greatly reduced. This lack of water clarity creates problems for fish and wildlife feeding. If water clarity is very bad sunlight will not be able to reach submergent plant species. Thus, they cannot photosynthesize and die.

As shorelines are eroded soil particles settle on the lake bottom. This process is called sedimentation. Sediment and eroded soils can also be carried through storm sewers, washing soil and nutrients from one’s own back yard into a lake. As sediment collects it covers the plants and bottom habitat of a lake that is so essential to invertebrates to feed on. Sedimentation is detrimental to both the lake food web and the harmony of nutrient levels.

Solutions

Establishing a Buffer Zone

Creating a buffer zone both along the shoreline and in the upland area can solve many lakeshore problems such as soil erosion, sedimentation, and excessive lake phosphorus levels. Choosing to create a sustainable lakefront is simple and biologically sound. Once a buffer zone is established lawn maintenance will be greatly reduced as mowing will no longer be necessary near the shoreline.

The process is simple: First, identify native vegetation species prevalent in your area. If no native species are prevalent or if you are unsure contact the Minnesota DNR or other human resources (available in the resources page). A shoreline buffer zone should contain native trees, shrubs, wildflowers, sedges, emergent and submergent aquatic plants. It is important to establish a diverse buffer zone of plants as they are all critical to the protection of the lake. There is no good way to control which species proliferates more; the plants should naturally proliferate and diminish as necessary.

A buffer zone is an area that extends from 25 to 100 or more feet from the water’s edge. The deeper the buffer zone the more protective. Narrow zones may be eliminated due to wave action. Your buffer zone needs to be comprised of two components: aquatic plants and upland plants above the water line. Wildflowers and sedges placed at the water’s edge and dry soil flowers, grasses, and shrubs in upland areas.

The goal of a buffer zone is to reduce the amount of soil erosion which can pollute a lake greatly. The roots of the native plants will stabilize soil and take up water from lower soil layers. A canopy of trees and shrubs intercepts rain and reduces the erosive force. Once rainwater advances to the ground level, the structure of grasses and wildflowers slows the flow and soaks the rainwater into the ground. The entire buffer zone will trap fertilizers, chemicals, and potential pollutants before they are able to entire the surface water of a lake.

Do not forget, buffer zones are beautiful! A buffer zone can restore a lakeshore’s natural beauty and aroma. The diverse plants will present a feast for all the senses, whereas a Bluegrass lawn cut short right up to the edge of a lake cannot.

Design, Preparation, and Installation
Designing Lakeshore Landscapes

- Produce "master plan" or design
- Divide property into small sections and plant one area at a time
- Plant in phases
- Develop a plant list: Look at native landscape of the area surrounding (shoreline and upland). Look for areas similar to your property. A good reference for native plant listings is Wetland Plants and Plant Communities of Minnesota and Wisconsin.
- Consider needs and desires: 1) characteristics of your site: (soil types, moisture levels and water depth, how does the lot drain, how much light, wind/wave action) 2) Utility requirements ( path to lake, place to store dock/canoe/etc, lighting, how much lawn) 3) recreational desires: (volleyball? Flower garden, fishing dock, more privacy, etc) 4) improvement of environment and water quality: (reduce amount of lawn, stop erosion, plant for wildlife).
- Draw base map
- Design specific Plantings: examine what might naturally grow in the area and think about planting that. Native plants would naturally fit the best into the growing environment on property and require the least maintenance and provide the best wildlife habitat. Break the landscape into distinct planting zones (buffer- 25-100 feet out from shore and into the water as far as vegetation will grow. Aquatic buffer zone: Emergent, submerged, and floating aquatic plants in lake and along shore absorb wave energy and hold bottom sediments in place while providing food and shelter for fish and wildlife. It is especially important to model natural surroundings in shallow areas with less wave action. Upland Buffer Zone: Think about leaving the vegetation along the shore un-mowed. Vegetation with good roots holds soils in place. Vegetation above this with different types of stems can act as filter by catching debris and absorbing nutrients carried in storm water- herbaceous and woody plants here. Herbaceous plantings: low-growing, non-woody, leafy, ground-layer plants. Grasses and sedges are very important to this zone. Wildflowers are a very nice addition to this zone, especially aesthetically. When considering woody plantings, as is the case for all plantings, you are simply best off just copying nature.

Site Preparation & Plant Installation

- Sources of native plants: Nurseries, Ccntract growing, digging from the wild, rescuing plants from construction, propagation from seed, cuttings, and rootstock.
- Site preparation: Get rid of invasive weeds, eliminate turf (easiest way: organic herbicide, tilling unnecessary) soil preparation (none required for native plants)
- Planting tips: 1- for affordability do one small section at a time. 2- Plant emergent/floating aquatic vegetation in the spring after water levels have lowered. 3- label a few plants of each species. 4- grow some native plants in small compartmentalized containers. 5- thoroughly soak containerized plants before taking them out of their pots to plant. 5- dig the hole wider than the root ball but not any deeper. 6- don't plant too deep or too shallow, the root ball should exactly match the existing soil surface. 7- water thoroughly after planting. 8- planting in lake where there are waves requires anchoring plants.
- Seeding tips: 1- till before seeding 2- not recommended within 15 feet of lakesore because of erosion 3- add cover crop of oats or rye 4- on shallow slopes and flat grades add some straw to prevent erosion and hold moisture 5- keep new seedings moist 6- have patience.
- "No planting" technique: some upland areas require no planting of native species, once lawn and competition is removed they will naturally fill in themselves. The key is native species adjacent and no adjacent invasive weeds.
- Mulching: prevents erosion and locks in moisture and controls weeds and creates barrier to wind and heat. Mulch shouldn't be so fine that it washes away or so coarse that it prevents anything from growing. Shredded hardwood works pretty well and can be used for both woody and herbaceous plantings. Straw also works well in herbaceous plantings. Wood chips and cocoa hull mulch are bad because they float and are easily washed away. Manure and compost are greatly discouraged because nutrients from them easily wash into the lake. Herbaceous plantings should have no more than 1 inch of mulch. Keep it about a half inch away from plant stems. Trees and shrubs should be mulched with tangled wood fiber and it can be up to 3 inches deep. Don't mulch right on shoreline because it could get washed into the water.