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How do you remove algae from ponds and lakes?

Planning an Excavated Pond:

Design of an excavated pond is based on the required storage capacity, depth to the water table, other available water sources, and the stability of the side-slope materials. The topographic conditions at the site must allow economical construction. Cost is a direct function of the volume of excavated material required to obtain a certain storage capacity in the pond. This method of construction results in the limited practical size of excavated ponds. However, these ponds can be designed to minimize evaporation losses by decreasing pond surface area in proportion to stored volume.

A rectangular shape is usually the most convenient for excavation equipment. The size of the pond is determined by the purpose for which water is needed, the site conditions, and the amount of inflow that can be expected. The required capacity of an excavated pond fed by a shallow water table is difficult to determine since the estimated rate of inflow into the pond can rarely be estimated with reasonable accuracy. Long narrow ponds will yield (or lose) more water from (or to) the surrounding area than square ponds. In some cases it may be necessary to augment the pond volume with water pumped from a nearby well or other water source. More information on pond sizing can be found in IFAS Extension Bulletin 257.

The proposed pond site should be thoroughly investigated prior to design and construction. Core samples of the soil profile should be obtained to provide information on the permeability of the material within all depths and below the bottom of the proposed pond. Permeability requirements for pond construction vary with the type of water supply into the excavated area. For a pond supplied by a surficial aquifer source the permeability of the surrounding soil must be high to assure sufficient inflow into the pond. Conversely, a pond supplied with water from another source as discussed above must be located in an area with low permeability soils in order to avoid seepage losses.

Permeability is defined as the readiness with which soil transmits water under standard field conditions. It depends primarily on the size and shape of the soil grains, the porosity of the soil, the shape and arrangement of the pores, and the degree of saturation. There are several laboratory methods to determine permeability for a given soil.

Indications of soil permeability can also be obtained at the sites by filling test holes with water and observing the seepage characteristics of the material. Permeability tests performed in the field are frequently more representative of the actual site conditions since the soil is not disturbed as much as when the samples are transferred from the field to the laboratory. The simplest method used in the field in the presence of high water table is to dig an auger hole into the soil below the water table. First determine the elevation of the existing natural water table by allowing the water surface in the hole to reach equilibrium with the surrounding area. Next, the water in the auger hole is pumped out to lower the elevation of the water surface in the hole, then the rate of rise of water in the hole is measured. From this measurement soil permeability can be calculated.

At sites without natural water tables, other permeability tests must be used. An infiltration test over a large area (13 ft or 4 m in diameter) may be used as a field test. This avoids the soil compression that is inherent in core sampling, which is necessary for the lab samples. The area is diked with a ring of soil and filled with water to form a shallow pond. A circular pond is recommended rather than a rectangular one because the circular pond has less lateral and undesirable seepage loss per unit area than a rectangular one. To perform this test water is added to the pond area as needed to saturate the soil in the surrounding area, then the falling water level of the pond in the absence of added water is observed and used to determine permeability. This rate should be a measure of the ability of the soil to pass water into and through the observed soil layer.

When excavated ponds are supplied by surface runoff or by water pumped from a well, relatively impervious soils at the site are essential to avoid excess seepage losses. Soil materials must be available to provide a stable, impervious fill where needed. Clays and silty clays are the most desirable, however sandy clays may also be satisfactory. In some regions of the Florida Panhandle, the soils contain sufficient clay to allow pond construction without adding soil amendments or artificially lining the pond. Unfortunately, most of the soils in peninsula Florida are very sandy, and additional measures to prevent seepage are necessary for pond construction. In some cases the only solution may be an artificial lining material. An artificial lining is expensive but should be considered at sites where soils are porous or are underlined by sands or gravel. Methods of pond sealing are discussed in IFAS Extension Circular 870.

In addition to permeability tests, the core sample holes may be used to determine the existing level of the water table from the shallow aquifer. The depth to the water table generally varies throughout the year. Therefore, several observations may be necessary to help with design. The performance of other nearby ponds may provide useful information with respect to the suitability of the proposed site and for design purposes.

Larger ponds should be equipped with some drainage facilities. A drain pipe is necessary to facilitate maintenance and fish management. On flat topography a pump may be necessary to drain the pond.

Excavated Pond Construction:

Proper construction practices should be followed to ensure safety and to reduce potential problems. After the pond site has been selected, an area or areas for spoil placement (excavated material) should be located. Stake the boundaries of the pond and spoil placement locations with the depth of cut from the ground surface to the pond sides or bottom clearly marked on the stakes. All woody vegetation should be cleared from these areas.

The type of excavating equipment for construction will depend on availability, climate, and physical conditions at the site. During dry periods most types of equipment can be used. The most common are tractor-pulled wheeled scrapers, draglines, and bulldozers. Inefficiency in transporting material limits the use of a bulldozer for excavation to relatively small ponds. Dragline excavators are commonly used for pond construction in the high natural water table areas of Florida. This is the only type of equipment that will operate under saturated soil conditions.

It is desirable to keep topsoil separated from subsoil materials during excavation. Place topsoil material in a location where it can be accessed after excavation has been completed. After excavation, this material should be placed on the surface of the side slopes, berms, spoil banks and spillways. These areas should be seeded or plugged with a grass or other cover material for erosion control. The grass or cover material should require minimal maintenance, be tolerant to local drought or wet conditions, and be relatively easy to establish.

Farm Pond Safety

The farm pond has been an important economic unit in many farming programs. Ponds are used as part of a soil and water conservation program to water livestock, as an irrigation water source, and for fire protection and recreation, such as fishing, boating, swimming and ice skating.

Unfortunately, farm ponds contribute to accidental drownings. Children are the victims of the majority of farm pond drownings. Small children get too close to the water and lose their balance on the soft bank. Many wade in the cool shallow water only to fall into deep holes. Some drown for no apparent reason. Lack of close adult supervision contributes to pond drownings.

Adults often overestimate a child's curiosity. A short attention span, coupled with the attractiveness of a farm pond as a play area may render most verbal instructions ineffective. Adults, too, drown in farm ponds. Most of these pond drownings occur while swimming. These are most often young active adults and visitors.

It is the farm operator's responsibility to see that his/her farm pond is as safe as possible. In most cases it is recommended that all ponds be fenced and posted to keep out unwanted persons. Liability may increase with non-posted, non-fenced ponds. Restrict entry to your pond to keep out uninvited guests.

Accidents can be prevented and lives saved by placing signs warning of specific dangers or indicating safe areas for swimming.

All farm ponds used for swimming should have a rescue post. It should be set firmly in the ground near the water. The post should be painted yellow. Attach a long shelf bracket, peg or nail to the post. Obtain enough nylon rope to reach across the pond. Attach a life buoy or ring to one end of the rope and a wooden block to the other end. Hang this rescue device on the post. A thin, lightweight 12' to 14' pole should be attached to the rescue post to aid in rescue. Finally, attach the location of the nearest telephone and emergency numbers to the top of the post.

It should be emphasized that all farm ponds may not be suitable for swimming. If the water is cloudy, has a foul odor or excess algae, it may contain infectious agents or be contaminated by fertilizers, pesticides or livestock wastes. Ponds used for swimming should be analyzed for bacteria during swimming season to determine water quality. Contact your county office of Ohio State University Extension for publications AEX 314, Water Testing and AEX 315, Where To Have Your Water Tested.

Make Your Farm Pond Safe for Swimming

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This page was last updated on November 16, 2002