By Patrick Simmsgeiger, Founder of DWI
The summertime beauty and function of a pond, lake or water feature can be seriously threatened by problems that actually develop during the winter, Algae, aquatic weeds, fish kills and odors are all caused by a buildup of debris and a lack of oxygen- conditions that develop during the fall and winter. The time to start preventing summer disasters is spring.
Setting the Stage
The water in our lakes is actually a solution of various chemicals and contains suspended organic materials. Various techniques enable water to achieve equilibrium; that is, the state in which natural decomposition is balanced by the amount of chemicals and organic materials entering the water. A program of clarification, proper water circulation and sunlight suppression can correct winter contamination. These measures are far more desirable than severe ones, such as dredging and mechanical weed control.
Many things happen during the fall and winter that disrupt the equilibrium of water bodies. Some of the most obvious are increased debris from trees and activity from migrating and native waterfowl. Some occurrences are not so noticeable. Precipitation increases during the winter. Rainfall, which contains a surprising amount of nitrogen picked up from the atmosphere, can change the chemical balance (pH) of water bodies. In addition, runoff from rainfall moves fertilizers and debris from the watershed into the lake.
More important, the process of biodegradation slows during the winter. The organisms in the water that break down leaves, bird waste and dead fish function very slowly, if at all. They simply can’t keep up. When temperatures rise in the spring and summer, the contaminant load in the water is very high. These organisms require oxygen and a certain pH range to do their job. Water holds only so much oxygen, depending on the temperature and circulation in the water. The more oxygen consumed by microorganisms, the less available for fish and other water life.
Fertilizers applied during the fall and winter also break down much more slowly. Landscape contractors apply nitrate forms of fertilizer (ammonium nitrate and calcium nitrate) to enable plants to obtain nitrogen and remain green during the cooler times of the year. Consequently, the potential for fertilizer runoff is greater during the winter. Nitrates that reach water bodies encourage the establishment of aquatic weeds and blooms of algae later in the season.
Add it all up, and you can see that the water in lakes, ponds and water features needs help in late winter and spring. Lake health depends on spring renovation.
Spring Lake Renovation
The goal of spring renovation is to bring the body of water back to equilibrium before high summer temperatures. and sunlight favor aquatic weeds and algae. To do this, you must reduce organic matter suspended in the water, adjust the pH of water to favor chemical breakdown and improve oxygen content. Other steps can be taken to improve lake health and discourage weeds, such as increasing lake depth and circulation; using dyes to reduce sunlight penetration; and preventing runoff and debris from reaching the water in the lake.
Reducing organic matter involves filtration or treating the water to cause organic particles to settle to the bottom. Filters are mechanical devices that require pumps, piping, a filter medium and power. The equipment must be operated and maintained properly, and the filter media must be flushed or replaced regularly to be effective. The time between filter maintenance events is determined by the load of suspended material in the water and the volume of water passing through the filter.
Treating a lake with chemicals requires sufficient circulation and an accurate calculation of the volume of water in the lake. The product needs to be both effective and safe for fish and irrigation if the lake is used as a reservoir. It must be applied correctly and evenly distributed throughout the body of water. For these reasons, selecting a professional applicator familiar with treating lakes is extremely important.
Clarification treatments should be followed with other steps to reduce light penetration and increase oxygen circulation. And, of course, now is the time to get serious about preventing debris from trees and lawns from entering the body of water.
The acidity or alkalinity of a lake influences how rapidly organisms function to digest contaminants. These organisms perform best at a certain range of a measurement called pH, which represents the amount of hydrogen present in the water. A balanced pH is 7.0. Tree leaves and rain can make the lake water acidic. However, a lake with a limestone shoreline can become too alkaline. The lake pH can change over time and reduce the effectiveness of beneficial organisms. The lake can be treated to restore proper pH.
Lake Depth, Weeds and Oxygen
Depending on the size and depth of the water feature, some provision should be made to maintain circulation throughout the year. Circulation distributes oxygen through the entire volume of the water, improves decomposition of organic matter and helps the lake maintain an even temperature at all levels.
A lake should be deep enough so that sun does not encourage establishment and growth of bottom-rooted weeds. Seed for these aquatic weeds can be deposited in the lake by wind or from bird droppings. Lake dyes can be used to prevent the sun from reaching the lake bottom and to impart a bluer cast to the water.
Deep lakes can develop stratification, or layers of water at different temperatures. The temperature of each layer determines how much oxygen it will hold, with cooler water holding more oxygen. Circulating water in the lake mixes the layers and makes the oxygen level consistent throughout the entire body of water.
Water that doesn’t circulate will also tend to hold more suspended material, which leads to discoloration and odors. Circulation causes suspended material to fall to the bottom of the lake where bacteria can break it down. Certain treatments can also cause suspended material to drop out.
When the amount of contamination entering a lake is impossible to control, a filtration system might be necessary. Filters are designed to catch a certain size of material. The right filter medium is needed to provide filtration at the most economical cost. Filters are also an additional maintenance concern.
Fountains and Injectors
Floating, motorized pumps can be installed in lakes either to pump air into the water (injector) or to pump the water into the air. Although pumps will provide additional oxygen, they also increase the water temperature so that it is more like the temperature of the air above it. The air pumped into a lake will not be distributed evenly throughout the lake without proper circulation. An injector that uses a pump on the lakeshore can also inject oxygen into the lake through tubes stretched across the lake bottom. All these devices take energy to run and require maintenance to operate properly.
Hidden activity beneath the surface of a water feature means that maintenance during the winter and spring is necessary to prevent serious problems in the summer. Because lakes contribute to our enjoyment and add to the property values, they are worth the investment in maintenance by knowledgeable professionals.