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Lake & Pond Management - Special Considerations

While previous sections of this web site deal specifically with the practical symptomatic approaches to controlling aquatic plants, other considerations may be involved in managing a body of water. Some understanding of watersheds, pond construction, water chemistry and fisheries biology can be useful in protecting, renovating and/or enhancing the water resource. It must be kept in mind that any biological, chemical or physical alteration made in the aquatic environment will have inter-related impacts.

Therefore, it is important that any management technique implemented be done carefully and with forethought as to what factors may be affected. While some bodies of water can support multiple-use activities, others are limited to specific purposes. The ideas presented here are intended to assist in maximizing their recreational, functional and/or aesthetic value.

Pond Construction Considerations

PLANNING

Careful planning in the design and construction of a pond can prevent many future problems. It is best to consult with professionals such as the Soil Conservation Service, Agricultural Extension, State Fish and Game Department and private engineering consultants to ensure both the feasibility and legality of construction in the area being considered. In some states, financial assistance may be available under water conservation or wildlife protection programs.

SITE SELECTION

The location and size of a pond will be dictated by the type of landscape (topography), soil structure, quantity and quality of water sources. These factors will determine whether a pond will be an excavated (tank-type) or an embankment (dammed) impoundment.

Ponds can be constructed where groundwater supplies are near the surface, where well water supplies or springs are available, in low-lying areas where run-off from the surrounding watershed (drainage) area is sufficient, or at the foot of streams. Some ponds may have to be constructed in a specific area out of necessity for storm water retention, fire protection or decoration, thus precluding some of the factors that might be considered in choosing an ideal site. In these situations, special measures may have to be taken such as using pond liners or sealants, providing supplemental water sources, or designing artificial water drainage systems.

Generally, it is not recommended (nor legal) for individuals to dam permanent streams. Groundwater supplies generally offer the highest quality water. However, if surface water sources are used, they should come from a well-vegetated watershed area.

Supplemental water sources, such as wells, may be necessary in some areas to maintain water levels or to periodically add fresh water. Water can be pumped in through standpipes to help function in aerating the water.

Soil composition of a pond bottom and banks should be of a nonporous material such as packed clay to prevent seepage. This is particularly important in dams. If suitable materials are not native to the area, commercially available clays such as Bentonite can be used.

Construct shorelines with a minimum of 1:3 slopes to discourage vegetation growth. A sufficient portion of the pond should be at least 10 feet deep. This will help prevent both aquatic plant growth and the potential for winterkill of fish under the ice in northern areas.

Install a drainpipe in the pond bottom, if feasible. This will allow lowering of water levels to repair leaks, re-excavate, or to remove trash fish.

Spillways are necessary in embankment ponds and might also be considered for excavated ponds. They provide an outlet for excess water that would otherwise erode shorelines or cause property damage from flooding. Determining the design, size and construction of dams and spillways are tasks best left to professional construction engineers.

CONSTRUCTION

In constructing a pond, it is advisable to remove all topsoil, brush and trees from the basin. Trees within 25 feet of the pond's edge should also be removed to prevent leaf litter from accumulating. Topsoil can later be used to cover banks before sodding or seeding with a fast-establishing perennial grass.

The following are several helpful hints to be considered. A narrow path of mounded soil near the pond's edge (called a berm) will serve to trap eroded materials, which might otherwise wash into the pond. All dams and embankments surrounding the pond should be free of stumps and brush to prevent leakage as this material decomposes. A filter bed of rock and rough gravel can be placed in areas where water is channeled into the pond. Finally, if water from the watershed is more than sufficient to maintain the pond level, a diversion ditch can be constructed to prevent some of the water from entering.

LEAKAGE

Seepage of water from a pond may become a problem when soils are too porous or are improperly compacted. Sealing of a pond may become necessary. Techniques include compaction, application of clay sealant, addition of chemical additives or installation of waterproof linings. Consult a soil expert or consultant to determine the best method.

By following the practical management and maintenance procedures described elsewhere on this website, a pond can offer many years of recreational enjoyment or functional use. Problems should be dealt with as they develop to avoid costly renovation.

Understanding Water Quality

Surface water is never found in a pure state. Even the cleanest lake or pond will contain various concentrations of dissolved gases, salts, minerals, metals and organic compounds. Most waters are teeming with microscopic plants, animals and bacteria along with suspended sediments and organic matter. Water quality is determined by the collective interaction of these chemical, physical and biological components. Some of the more important water quality parameters, and their relation to the “health” of a lake or pond, are discussed below. Corrective measures for some problem situations are also included.

Dissolved oxygen concentrations are an important gauge of existing water quality and the ability to support a well-balanced aquatic animal and plant population. Through the natural mechanisms of aquatic plant photosynthesis and surface absorption, oxygen is constantly being added to the water. At the same time, there is a continuous consumption of oxygen taking place throughout the water column by fish, zooplankton (the microscopic animals upon which small fish feed), aquatic insects, snails, crayfish and a diversity of other swimming and bottom-dwelling organisms. Competing for this same oxygen are multitudes of bacteria which utilize oxygen in the decomposition of organic materials (dead plants and animals, fertilizer, animal wastes, run-off water contaminants, septic seepage, etc.) entering or within the system. Aquatic plants may compound the oxygen balance problem by using, instead of producing, oxygen. This occurs during the night, under extended cloudy periods or beneath snow and ice cover.

As a result, variations in oxygen content occur from the surface to the bottom and also from day to night. In addition, seasonal variations occur which affect chemical and biological cycles within the entire water body. When water temperatures are equal throughout the water column in spring, surface and bottom waters will mix. This distributes dissolved oxygen vertically and horizontally, virtually equalizing concentrations throughout the water. As the surface warms by the heat of the sun, layering begins to develop. Cooler, denser water is trapped at the bottom while lighter, warmer water remains near the surface. This temperature-based layering, known as thermal stratification, creates a natural barrier to vertical mixing within the water column. Within or near the bottom sediments, dissolved oxygen concentrations may become depleted. Meanwhile, surface water remains oxygenated through absorption and horizontal mixing by wind action. Fish and other beneficial life forms are then restricted to this surface stratum.

The cooling of the surface water in fall will eventually break down this stratification. This again allows complete mixing of surface and bottom waters and re-oxygenates the water column before the onset of winter. In areas where an ice cover forms, absorption of oxygen from the atmosphere ends and virtually all mixing comes to a standstill. Under the ice, life becomes totally dependent upon existing dissolved oxygen and that produced by surviving vegetation. If thick ice or snow cover shuts off sunlight, plants will die or respire and become oxygen users instead of producers. When oxygen demand exceeds supply, a winterkill of fish and animal life occurs.

Generally, a minimum of 5 mg/L dissolved oxygen is required to support warm water fish and 6-7 mg/L for cold water species. Dissolved oxygen is also essential to the efficiency of the decay process on the bottom. If oxygen is depleted, microbe populations switch from aerobic (with oxygen) to anaerobic (without oxygen). The by-products of anaerobic decomposition are noxious, malodorous gases such as hydrogen sulfide ("rotten egg" odor) and methane. Due to inefficient breakdown of dead plant and animal materials under these conditions, a black muck or sludge will form on lake and pond bottoms.

Aeration equipment can be installed to overcome oxygen deficiency problems. Benefits of proper aeration include:

prevention of winter/summer fish kills
fish habitat promotion/expansion
elimination of noxious anaerobic gas build-up
improved water quality
reduction of certain nutrient problems due to oxygenated benthic (bottom) interactions
increased decomposition of organic materials in an aerobic bottom layer
complete de-stratification of the water column equalizing temperatures and oxygen concentrations throughout the lake or pond.

Normally, this is only practical in ponds and small lakes. Aeration of large bodies of water can be difficult, and if the installed system is not sized properly, increased nutrient cycling may occur.

Numerous types of systems are commercially available including:

compressed air systems (systems pump air from shore through tubing to diffusers on the bottom)
bottom and floating horizontal aerators (force water movement horizontally)
floating vertical aerators and fountains (pumps water vertically into air).

Of primary consideration are the energy efficiency and the rate by which oxygen is distributed throughout the water column. Vertical water pumping systems, while decorative, are costly to run and are slow to disperse oxygen in larger bodies of water. Compressed air systems provide an effective, cost-efficient and flexible means of adding oxygen while moving and mixing the water. Horizontal aerators have similar energy requirements to those of vertical aerators, but have the ability to mix water in shallow stagnant areas where other systems may be ineffective.

Sizing and placement of equipment may vary with the size, depth and configuration of a body of water. In addition, timing of installation must be considered to avoid too rapid of a change in conditions. Therefore, it is recommended that lake and pond owners contact the manufacturer or a consultant prior to installation.

It should be noted that aeration is not in itself effective in controlling aquatic weed and algae growth. The only benefits in this regard may be a shift in species from noxious blue-green algae to green algae, and oxygenated benthic interactions may prevent certain nutrients key to aquatic growth from re-entering the water column. Note that any nutrient reduction may not be sufficient to eliminate aquatic growth problems and will not prevent nutrient recycling through rooted aquatic plants.

Water fertility is determined by the amount of dissolved nutrients (mainly nitrates and phosphates) available within a body of water. The productivity or degree of vegetation growth is directly related to water fertility. Lakes and ponds with high nutrient levels are called eutrophic and the process of nutrient enrichment is called eutrophication. At any point in time, nitrogen and phosphorous might be found within bottom sediments as a component of plant and animal tissue or dissolved within the water. Seasonal variations are common, as these nutrients are recycled within the aquatic environment from one form to another.

Controlling outside sources of nutrients plus reducing those already within a lake or pond is a long-term idealistic approach towards eliminating the main cause of overabundant plants. Attempts at doing this have been met with mixed success. Limiting nutrient input from sources within the watershed can range from making a few simple alterations around a pond to redesigning sewage systems and agricultural lands along drainage systems entering a lake.

Microbial bio-augmentation techniques can be utilized to try to establish an additional aquatic food web component to limit nutrients available for aquatic plant growth. By limiting soluble phosphorus and nitrogen, the amount of algal growth may decrease and a shift of species may occur. In addition, the reduction of soft organic sediment that may occur would limit the nutrient sink utilized by rooted vegetation. Success using this method has been seen by applicators, but only in conjunction with proper management of the surrounding watershed and proper aeration (discussed under dissolved oxygen).

Technology is available for reducing or inactivating dissolved phosphate through the addition of 100 to 160 pounds of aluminum sulfate (alum) or 40 to 120 pounds of ferric sulfate per acre-foot. These chemicals precipitate or are lost from solution, taking available phosphates with them. The amount required is dependent upon the existing concentration of phosphorous and the pH of the water. Actual dosages are best determined by laboratory analysis. Overdosing could result in drastic pH change and a loss of fish life. Professional assistance is encouraged. Removing nutrients from the water column will have a particular effect upon reducing algae and free-floating plant growth. A more limited effect will be seen on rooted plants since they can derive nutrients from the sediment. As an additional benefit, alum and ferric sulfate will act as water clarifiers by removing particulate materials suspended in the water column.

Turbidity refers to a measure of the relative clarity of water. Turbidity or muddy water is often caused by suspended silt or clay particles, which diffuse or scatter light. As a result, light does not penetrate through the water column and the water appears unclear. This should not be confused with discolored water, which sometimes results from dissolved materials such as organic acids from leaf litter.

Erosion of soil along shorelines or within the watershed is a primary contributor to excessive turbidity. Poor construction or farming practices is often to blame. Wind and wave action or the disruption of bottom sediments by carp and bullheads can create or contribute to the problem.

High turbidity will reduce light penetration and retard bottom plant growth. It may also have the negative impacts of irritating fish gills and impairing spawning and predation success. Turbid water is typically poor for game fish production and undesirable from an aesthetic and recreational standpoint.

Microbial bio-augmentation methods may be able to reduce suspended organic solids by the microorganisms breaking down the material into gases and/or bio-mass. Proper aeration (discussed under dissolved oxygen) and proper watershed management practices should be in place. This method will not have affect on inorganic suspended solids such as clay.

Application of flocculants such as ferric sulfate or alum (discussed under water fertility) or use of agricultural lime or gypsum at 1,000 pounds per surface acre will help clear water. It is best to add these materials gradually to avoid rapid environmental changes. Some experimentation or consultation with professional help is also recommended. Turbidity will be a recurring problem unless the source of the sedimentation is corrected.

Alkalinity and pH are important measures of the "chemical balance" within water. The types of aquatic life present are in part governed by these two parameters. Alkalinity is a measure of buffering capacity or the ability to tolerate the addition of acids or bases without appreciable change in pH (a measure of the water's relative acidity). Water's relative acidity (its pH) is based upon a logarithmic scale of 0 to 14 with 7 considered neutral, measurements less than 7 are acidic and measurements above 7 are alkaline.

Generally, pH and alkalinity are dictated by the chemical make-up of bottom sediments, surrounding soil and water entering the system through run-off or rainfall. The interrelationships between carbon dioxide, bicarbonates and carbonates (a process too complex to explain here) determine pH and alkalinity. Suffice it to say that waters in limestone regions or where minerals are easily dissolved will contain carbonates and bicarbonates. These are typically termed hard water areas and will be alkaline. Lowland bog areas, mountain lakes or those located in bedrock areas will contain free carbon dioxide. These are referred to as soft water areas and waters will be near neutral to acidic.

Most freshwater life prefers a pH range between 6.5 and 9.0. Different organisms have varying tolerances. Relatively rapid changes in pH can occur in soft water and are typically low in production of aquatic life. At the other end of the spectrum, higher alkalinities are associated with increased productivity. Algal blooms can serve to raise pH by utilizing the free carbon dioxide being absorbed from the air.

Raising or lowering pH in a body of water is done on rare occasions. Some acid lakes affected by acid rain have had their pH raised through the addition of lime. This is a temporary solution and may require maintenance applications. Newly dug ponds are occasionally limed to establish a higher potential for fish production. These management techniques are not recommended unless under the guidance of an expert.

Coliform bacteria are important indicators of contamination from animal and human wastes. Determining their presence is particularly important in waters used for swimming, domestic use or drinking. High levels of these bacteria raise concern over the potential existence of pathogenic (disease-type) bacteria and viruses. Since they are short-lived organisms, their presence indicates recent contamination.

State and federal guidelines have been established that determine what levels are considered safe for body contact, drinking or domestic use. Water samples must be collected in sterilized bottles and tests should be run by a certified laboratory. Multiple tests are done at varying frequencies to crosscheck results. Frequent occurrence of high levels may require closing of swimming areas and the need to correct septic or sewage discharge sources.

Pollutants and contaminants from industry, agriculture and other sources can adversely affect water quality. Input can be airborne, contained in surface run-off and groundwater, or found within direct discharges. Examples which have received recent attention include PCB's (polychlorinated biphenyls), dioxins, heavy metals (mercury, arsenic, lead, etc.), hydrocarbons and pesticides.

Some pollutants can be detrimental to aquatic life and may even pose human health hazards. They can accumulate within bottom sediments or may be recycled within the food chain. A build-up can occur within the flesh and tissues of gamefish, making them unfit for human consumption. Other contaminants will be directly toxic to the organism itself or cause poor growth and reproduction.

The watershed and direct, in-flowing water (rivers, ditches, pipes, etc.) must be examined closely for potential sources of contamination. Use of agricultural pesticides and fertilizers on surrounding land must be done with care. Herbicides, not specifically labeled for aquatic use sites, should never be introduced for weed control in a lake or pond. If specific contaminants are suspected within the water or sediments, sophisticated testing with highly sensitive equipment at a reputable laboratory is advised.

Understanding Fish Management

Fisheries management is the science of manipulating fish populations within a body of water in order to achieve maximum desirable production. Maintaining these populations requires that the species present must survive, grow and reproduce. The typical objectives for managing fish are for food and/or recreational resources.

Of primary concern is providing a suitable environment to meet the needs of the fish species' habitat and food requirements. Acceptable water quality is extremely important. Most of these parameters and requirements are discussed in the sections covered under “Understanding Water Quality”.

Warm Water

Largemouth bass
Striped bass
Sunfish (bream)
Crappie
Catfish
Bluegill
Minnows

Most warm water species will do well within a wide range of water temperatures from ice-covered waters to beyond 800F, although growth will be slower in cooler water. Cool water fish prefer temperatures ranging into the upper 60's (F0). Cold water varieties are best suited for temperatures below 650F. Within ponds or lakes, which thermally stratify, species from several of these groups may do well.

Other important considerations include providing hiding places for young fish and suitable substrate for spawning. These requirements vary widely with species, therefore, knowing the life history of each is important. Controlling aquatic plants to acceptable levels, as discussed in the first part of this book, is of primary concern in limiting cover. Too much vegetation will lead to an overabundance of small, stunted fish. Proper bottom materials (sand, gravel, etc.) or plant stems may be required for depositing eggs. In some bodies of water, cover or bottom materials may have to be provided. Structures, called "cribs", consisting of rock piles, fallen trees, or bundles of branches are sunk into the water for this purpose. Artificially constructed reefs and gravel bars may also be installed.

Decisions to stock fish must be based upon the conditions of the existing habitat and particularly take into account what fish are already present. Any given body of water will have a certain carrying capacity or maximum production. Simply adding fish to an existing population is rarely successful, unless there is an excess of food and unoccupied habitats. Suitable numbers of forage (food) fish must be present if larger predator fish are to survive. Choice of species and stocking ratios will vary geographically and by environmental conditions. Therefore, contacting the biologists at local fisheries or hatchery operators is recommended. Some may be able to provide a fisheries management survey to determine the existing balance and condition of the population.

Avoid the mistake of expecting to control a stunted panfish population by simply adding a number of large predators. (Hybrid or non-reproducing sunfish have become a popular alternative to avoid problems with overpopulation of stunted panfish). Similarly, do not assume that a gamefish population can be established within a body of water overrun with carp or rough fish. Either of these situations should be remedied with an eradication program of existing fish stocks. This can be done through draining or use of a fish toxicant such as Rotenone. If fish are stocked, obtain them from a reputable hatchery. Make certain that they are free of disease and healthy upon their arrival. Handle them carefully and as little as possible. The temperature difference between the holding water and the lake or pond should not exceed 100F. If it is, fish must be gradually acclimated.

The amount of fishing pressure required to sustain a balanced population will vary. Panfish can usually be caught when they reach desired size. Intensive removal of panfish may be required to avoid stunting problems. Similarly, size and catch limits might be imposed upon larger fish to ensure their numbers. However, it is best not to remove predator gamefish until after they spawn (approximately 3 years after stocking).

Except under exceptionally sterile conditions or where extremely high productivity is desired (such as aquaculture ponds), fertilization and feeding programs are not recommended. Properly managed waters contain enough fertility to support good fish growth. Addition of more nutrients may only lead to undesirable and uncontrolled weed and algae growth.

Keep records of fish stocking and a creel census of what has been caught. Examine fish periodically for signs of stress or disease. Check water quality regularly for signs of trouble. Consult an expert if problems are suspected.