Algae Control | Pond Aeration |
Malibu Water Resources Directory 2 |
Washington State: http://www.ecy.wa.gov/ |
Water Quality: http://www.ecy.wa.gov/programs/wq/wqhome.html |
See: http://www.ecy.wa.gov/programs/wq/plants/lakes/characteristics.html |
Chapter 1 - Lake CharacteristicsFormation: Geologic and human events
MOST LAKES were created by geologic events. The vast lake-dotted and marshy landscapes found in North America were formed by glacier action 10,000 to 20,000 years ago. Glaciers formed lake basins by gouging holes in loose soil or bedrock, by depositing material across streams beds, or by leaving buried chunks of ice whose melting shaped lake basins. More recently, humans and other animals have created lakes and reservoirs by damming rivers and streams.
Lakes constantly undergo evolutionary change, reflecting the changes that occur in their watersheds. Most are destined to fill in with remains of lake organisms and with silt and soil washed in by floods and streams. These gradual changes in the physical and chemical components of a lake affect the development and succession of plant and animal communities.
This natural process takes thousands of years. Human activities, however, can dramatically change lakes, for better or worse, in just a few years.
Hydrologic Cycle: How the water comes and goes
In Washington, about three-fourths of the precipitation that falls reenters the atmosphere by transpiration from plants and evaporation from the earth's surface. Much of the remaining water seeps or soaks into the ground water and moves underground toward lakes and rivers. Water that runs off the land surface also enters rivers and lakes.
Lake levels vary from season to season and year to year. Precipitation is the principal cause of lake level fluctuation. If rainfall decreases, the lake level falls; if rainfall increases, the lake level rises. However, the lag between precipitation and lake level change varies from days to years, depending on the lake. Dams can modify some fluctuations, but varying lake levels are normal.
Stratification: Layers of a lake
Water in lakes in temperate climates tends to stratify or form layers, especially during summer, because the density (weight) of water changes as its temperature changes. Water is most dense at 39 degrees Fahrenheit. Above and below that temperature, water expands and becomes less dense. Many lakes stratify in winter because ice covers the lake surface. Lakes in areas with milder winters do not stratify during the winter. In spring, as ice melts, the surface waters warm; sink; and mix with the deeper water, a process called spring turnover.
As summer progresses, the temperature difference (and density difference) between surface and bottom water becomes more distinct, and most lakes form three layers. The upper layer, the epilimnion, is characterized by warmer (less dense) water and is the zone of light penetration, where the bulk of productivity or biological growth occurs.
The next layer, the metalimnion or thermocline, is a narrow band--colder than the upper and warmer than the lower waters--which helps to prevent mixing between the upper and lower layers.
The (third) bottom layer, the hypolimnion, has much colder water. Plant material either decays or sinks to the bottom and accumulates in this stagnant layer.
During the fall turnover, surface waters cool until they are as dense as the bottom waters and wind action mixes the lake so that water temperature from surface to bottom is the same.
Oxygen: Essential to lake life
The presence of oxygen in lake water determines where organisms such as fish and zooplankton are found. In spring, when the lake water is well mixed, oxygen is usually present at all depths and organisms may be distributed throughout the lake. In the summer, under stratified conditions, little or no oxygen is produced in the hypolimnion. Available oxygen is consumed through decomposition of plant and animal material, and oxygen levels become too low for fish who must move to the top layer, or epilimnion.
If these conditions are prolonged and the upper waters become too warm, cold-water fish such as trout may become stressed and eventually die. In the fall, the lake layers break down and turnover replenishes oxygen to the bottom waters.
The formation of ice in water reduces the supply of oxygen to the lake from the overlying air. If oxygen levels fall too low, fish and other aquatic life may die.
Nutrients: Phosphorus and nitrogen
Plants require phosphorus and nitrogen for growth. The concentration of these substances in water and sediments control the total amount of plant matter that can grow.
In most lakes, phosphorus is the least available nutrient; so its abundance--or scarcity--controls the extent of algae growth. If more phosphorus is added to the lake from sewage treatment plants, urban or farmland runoff, lawn or garden fertilizers, septic tanks or other watershed or outside resources, or even if it is released from phosphorus-rich lake bottom sediments, more algae will grow.
Under certain conditions, especially when oxygen is absent from bottom waters, phosphorus is released from bottom sediments into the overlying water.
In turn, algae clouds water clarity and decreases the depth of light penetration. By measuring the phosphorus concentration, algae abundance (by chlorophyll analysis), and water clarity (by Secchi disk measurement), the so-called trophic status is identified.
A eutrophic, or nutrient-rich lake tends to be cloudy or green with algae and may have limited oxygen in the hypolimnion. An oligotrophic lake is relatively nutrient-poor, is clear, and has adequate dissolved oxygen in the hypolimnion. A mesotrophic lake is between the two. Factors vary from lake to lake, and designations of lakes as eutrophic; mesotrophic; or oligotrophic tend to be subjective.
Chapter Two - Lake ProblemsEutrophication: The aging process
OVER ITS LIFETIME a lake progresses from a more oligotrophic to a more eutrophic state. When nutrients such as phosphorus and nitrogen wash into a lake with stormwater or by soil erosion, they fertilize the lake and encourage algae and larger plants to grow. As plants and the animals that feed on them die and decompose, they accumulate on the lake bottom as organic sediments. After hundreds or thousands of years of plant growth and decomposition, the character of a lake may more closely resemble a marsh or a bog. This natural transition process is called eutrophication.
Lakes also obtain nutrients from various human activities, which can literally make a lake old before its time. This accelerated transition is called cultural eutrophication. Nutrients from agricultural areas, stormwater runoff, urban development, fertilized yards and gardens, failing septic systems, land clearing, municipal and industrial wastewater, runoff from construction projects, and recreational activities contribute to accelerated enrichment or eutrophication.
Sedimentation: Soils wash into the lake
Sedimentation is closely associated with eutrophication. Wind and water move soils from the watershed into a lake. The soils settle on the bottom of a lake, and the lake becomes increasingly shallow as part of the natural filling of the lake.
Sedimentation is greatly accelerated, however, by human activities that leave the soil exposed without vegetation for extended periods. Land development, construction and agricultural activities near lakes and streams, or farming steep slopes leaves soils vulnerable to erosion. Sedimentation is best controlled through soil and water conservation practices, maintaining vegetation on soils, and use of best management practices (BMPs) during construction.
Algae: Microscopic aquatic plants
Algae are a source of food and energy for fish and other lake organisms and a vital part of all lakes. Too many or nuisance types of algae, however, can interfere with lake uses by clogging the filters in water treatment plants, inhibiting the growth of other plants by clouding the water so that it shades them, contributing--as they decay--to oxygen depletion and fish kills, and causing taste and odor problems in water and fish. Some species of algae release toxins.
Excess algae can interfere with the simple pleasure of looking at a lake for its beauty. Unsightly scums are usually caused either by tangled masses of filamentous algae or by "blooms" of certain planktonic algae that float on the lake surface forming scums. The regular occurrence of visible algal blooms often indicates that nutrient levels, especially phosphorus, are too high.
Aquatic Plants: Large rooted or floating plants
Aquatic plants also limit many uses of the lake. Like algae, aquatic plants (macrophytes) are a vital part of the lake because they provide cover, habitat and sometimes food for fish, the organisms that fish eat, and other wildlife. However, too many rooted and floating plants can limit swimming, fishing, skiing, sailing, boating, and aesthetic appreciation. Excessive plant growth can physically prevent mixing of oxygen through the water.
When plants die they can introduce significant quantities of nutrients and organic matter back into the water, stimulating algal blooms and raising dissolved oxygen consumption. Macrophytes are grouped into classes called emergents (cattails and bulrushes), floating-leaved (water lilies and duck weed), and submersed (milfoil and pondweeds).
Submersed plants grow profusely only where underwater light is sufficient. Steep-sided lakes have fewer common nuisance weeds because most of the sediments are too far below the surface. Thick sediments can create a favorable weed habitat unless the sediment loading also creates severe water turbidity (cloudiness).
Most macrophytes obtain their nutrients from lake sediments via roots. Therefore, they can grow abundantly even in lakes in which the nutrient concentration of the water has been reduced.
Contamination: Pollution from toxic substances
Lakes can be contaminated by toxic substances including industrial chemicals such as PCBs (polychlorinated biphenyls), metals, and solvents; pesticides from agricultural runoff; urban stormwater runoff containing petroleum hydrocarbons, metals and pesticides; and air-deposited chemicals.
Toxic contamination may cause dramatic impacts such as fish kills. Less obvious impacts include decreased reproduction or slower growth rates in fish and reductions in invertebrate diversity. One long-term danger of toxic contamination is the bioaccumulation or build-up of toxic substances--mercury, for example--in fish flesh. The toxic efforts may be passed on to humans eating the fish.
Chapter Three - Watershed ManagementWatershed: Area draining to a lake
A WATERSHED is the area of land from which water drains into a given lake or river. A lake reflects its watershed because the watershed contributes both the water required to maintain a lake and the majority of the pollutants that enter the lake.
Effective lake management programs must include watershed management practices. Lake problems cannot be solved without controlling the sources in the watershed.Pollutant Sources: From pipes and run-off
Lake pollutants may originate from either point sources or nonpoint sources in the watershed. Point sources discharge pollutants from a distinct source such as a wastewater treatment plant or industrial facility. Point sources are usually regulated by state and federal permits.
Nonpoint pollutants include silt, nutrients, organic matter, and other substances originating over a relatively broad area. Water running over the land picks up these materials and transports them to the lake, either directly in runoff or through a tributary stream, drainage system, or ground water. Water running off a lawn or driveway during a heavy rain is nonpoint source runoff.
Land uses such as agriculture, construction, and roadways contribute higher nonpoint pollutant loads than other land uses such as forests. Nonpoint pollution sources are usually controlled by implementing best management practices.Point sources were traditionally considered to be the primary dischargers of pollution to water bodies. However, nonpoint sources (harder to identify, isolate, and control) are now more likely to be the principal contributors of nutrient and sediment loads to lakes.
Pollutant Source Assessment: Where pollutants come from
Not all areas of the watershed are equal pollutant contributors. By identifying those critical areas that contribute excessive amounts of soil and nutrients to the lake, the most effective controls can be developed.
For example, agricultural runoff carrying animal wastes, soil, and nutrients can be a critical pollutant contributor. Urban runoff from lawns, gardens, streets, and rooftops may be significant sources of sediment, oils and greases, nutrients, and heavy metals to lakes. Construction and forestry activities can provide significant quantities of sediments, especially during rainstorms.
In large watersheds, the contributions from urban, forestry, and agricultural areas are generally more significant than those from lakeshore homes. In small watersheds, lakeside resident activities may be more critical pollutant contributors.
Best Management Practices: Methods to control pollutant sources
Managers of lakes and streams focus on best management practices to control four primary processes: erosion and sedimentation, stormwater runoff, nutrient inputs, and pesticides or toxic substances. These processes are highly interactive.
For example, runoff control helps to reduce sediments, nutrients, and pesticide contamination in streams and lakes.Best management practices for urban areas would include flood storage and control, street cleaning, and use of porous pavements. Such practices for construction would include stabilizing soils and limiting disturbed areas. These practices are also important to agriculture and forestry. The best place for any lake resident to use best management practices is in their own backyard.
Chapter Four - Shoreline ManagementProtecting the shoreline
HOMEOWNERS AND LAKE associations can implement many practices that will help to reduce lake pollution and protect water quality. Appropriate landscaping, reduced use of fertilizers and pesticides, proper maintenance of septic systems, and judicious use of household products are discussed below. Before beginning any activity, think about potential pathways and risks to water quality from soil erosion, chemical amendments, and yard waste.
Shoreline Development: Lakeside Building
Shoreline development can hurt a lake. The shorelines and wetlands act as a buffer between water and land as they trap nutrients, filter pollutants, retard erosion, and provide habitats for plants and animals.
Shoreline development directly affects lakes in two ways. First, wildlife habitats and buffering capacity are lost through destruction of the natural vegetation around lakes. Second, pollution from increased surface runoff and nutrient additions from fertilized lawns and septic systems can affect lake water quality.
Landscaping: Lawns and gardens
Lawns and gardens adjacent to lakes must be carefully planned and maintained to prevent contamination of surface and ground waters. Consider native vegetation as a quality alternative to cultured lawns and landscapes because it provides a more diverse and balanced plant community and habitat. Contact a nursery that supplies native plants for species best adapted for your needs.
Shoreline Management Regulations prohibit intensive removal of vegetation near the shore or on steep slopes. Check with your local jurisdiction for specific regulations.
Take steps to offset problems which could occur under the following conditions:
Areas of exposed soil or poorly established vegetation.
Coarse textured soils such as sands or sandy loams.
Property sloping toward water.
Impervious surface such as sidewalks and driveways.
Lawn/landscape maintenance close to water.
Application of fertilizers, pesticides, or soil amendments.A balanced approach to waterfront landscaping retains some natural habitat and reduces pollution and erosion while also meeting your aesthetic and access needs.
Fertilizers: Growth stimulators
Avoid the use of chemical fertilizers if possible. Native vegetation does not require the application of additional fertilizer.
Compost or manure is preferable to chemical fertilizers; however, they can degrade (damage) water quality if used in excessive amounts.If you apply fertilizers to lawns and gardens, adhere to the following guidelines:
Have your soil tested to determine how much fertilizer is needed.
Water your lawn after fertilizing, but do not allow excess water to run off into surface waters.
Sweep up any fertilizer which is spilled on hard surfaces such as walks and driveways.
Be careful when applying fertilizer near surface waters. Do not spread fertilizer within 75 feet of surface waters or wetlands. Use a "drop" spreader and not a "cyclone" spreader to reduce the chances of getting fertilizer in the water.Pesticides: Insect and weed control
Avoid the use of chemical pesticides if possible. Consult a professional from the Washington State University Cooperative Extension Service to determine alternative methods for pest controls if needed.
The following practices will minimize the potential of contamination from pesticides:
Properly identify whether an insect, disease, or other factor is causing the problem.
Determine whether there is an economic or aesthetic justification to initiate control of the pest.
Consider controlling the pest without a pesticide.
Use the least toxic and most readily degradable pesticide.
Read the pesticide label carefully. Pay special attention to warnings about use near water and safety precautions.
Do not apply pesticides when it is windy to avoid the possibility of drift.
Purchase only what is needed to control the problem (this season).
Dispose of waste pesticides properly. Do not pour them on the ground or into storm drains, surface waters, or sanitary treatment systems. Consult with your local solid waste office for proper disposal methods.Landscaping: Example of a lake-friendly landscape plan
Riparian Zone: Lady fern, sedges (many species), blue flag iris.
Lower Bank: Shrubs: red osier dogwood, red elderberry, evergreen huckleberry Ground Covers: lady fern, bunchberry, sword fern; Shade Trees: chokecherry, Oregon ash, western hemlock; Shade & Cover: vine maple, western crabapple, hazelnut.
Upper Bank: Shrubs: serviceberry, mock orange, red flowering current; Ground Covers: salal, sword fern, pick-a-back; Shade Trees: chokecherry, Oregon ash, western hemlock, Shade and Cover: vine maple, western crabapple, hazelnut.
Septic Systems: They need to be maintained
Without routine maintenance a properly installed septic system should not pollute the lake. The following practices will reduce contamination from septic systems.
Have your septic tank checked every other year and pumped when necessary.
Use nonphosphate detergents, wash full loads of clothes, and use water-saving showers and toilets to avoid stressing your septic system.
Do not use a garbage disposal.
Do not use septic system additives. Keep solvents, plastics, paper diapers, and other similar products out of your septic system.
Do not pave over or park on your drain field. The soil needs to breathe.Hazardous Household Products: Cleaners can be toxic
Many common household cleaners and products contain ingredients that are corrosive, toxic, or flammable. When used or disposed of improperly, these products can affect personal health and safety and can also contaminate ground water and soil, eventually polluting our lakes.
Think before buying household cleaning and maintenance products. General purpose products may work as well as products developed for a specific surface or appliance. Purchase water-based nontoxic or less toxic products rather than solvent-based paints and cleaners. Alternatives to hazardous cleaning products are cheaper and some are equally effective. Information on these alternatives is available from the Washington State Department of Ecology.
If you must use a hazardous product, read the label carefully before purchasing. Make sure the product will do what you want it to. Buy only the amount you need. If you cannot use it all, give it to someone who can.
Exotic Species: Foreign invasion
Exotic species, organisms introduced into habitats where they are not native, are considered to be severe threats to our lakes.
They are a major cause of the continuing loss of biological diversity throughout the world and have caused extinction of some native species.The exotic zebra mussel. Be on the alert for these tiny invaders.
In the absence of predators, parasites, pathogens, and competitors from their native habitat, species introduced into new habitats often overrun their new home and crowd out native species. Once established, exotics rarely can be eliminated.
Examples of exotic species are common cordgrass (Spartina angelica), purple loosestrife (Lythrum salicaria) and Eurasian watermilfoil (Myriophyllum spicatum). State law prohibits the sale, distribution, or planting of these and other exotics.You can take the following actions to minimize the spread of exotic plants and animals:
Learn what these species look like and monitor for their presence. Report a new infestation to the Washington State Department of Ecology or your county Noxious Weed Control Board.
Do not introduce exotic species -- especially don't dump unwanted aquarium contents into a lake.
Remove plants and animals from your boat, trailer, and accessory equipment before leaving the water access area. Then wash all equipment with hot water. If possible, let everything dry for three days before transporting your boat to another body of water.
Chapter Five - Lake ManagementEVERY LAKE is unique. Specific strategies to address a lake's water quality problems should focus on activities in the watershed and/or in-lake restoration techniques, depending on the nature and extent of the problem.
Lake management approaches fall into two categories, the "quick-fix" and long-term management. The quick-fix offers a short-term solution such as the application of herbicides to kill unwanted algae or macrophytes (large plants). It treats the biological symptoms of a lake problem, but does not address the underlying causes. Plant and fish productivity are dependent on the chemical and physical processes going on in and around the lake, and these must be considered in any plan to change the biology of a lake.
Long-term management considers all of the environmental, cultural, and biological factors affecting the lake and sets a priority on finding lasting solutions. If immediate in-lake restoration techniques are necessary, they should be followed by appropriate long-term management actions to control sediment, nutrient, and toxic inputs.
Lake management is a complicated job and likely will be a joint effort of community groups, individuals, landowners, and government. To be effective, lake management is a long-term commitment and investment. This and following sections briefly summarize various methods to improve a lake's water quality and indicate necessary permits and possible grants and loans.
In-Lake Restoration: Cleaning up problems
Controlling pollution sources will not improve lake water quality immediately in many cases. Years may pass before lakes cleanse themselves of accumulated nutrient loads and wastes. For this reason, in-lake restoration techniques have been developed to accelerate recovery. In-lake restoration techniques are briefly described in the table below. Consult the references at the end of this web-site for more details on these techniques.
See: http://www.ecy.wa.gov/programs/wq/plants/lakes/lake_management.html |
