Pond morphology
Contact your area USDA-Natural Resources Conservation Service to have your site evaluated for vertical clay and sand content. Ponds constructed without proper planning may not hold water or have adequate access, and may have
persistent weed problems, be difficult to harvest, and be difficult to drain completely.
Information in this publication is based primarily on pond construction experience in the Delta
region of Mississippi, Arkansas and Louisiana. Please refer to SRAC publication no. 102, Watershed Fish Production Ponds, for information about constructing ponds in rolling terrain.
Commercial catfish ponds are being built deeper than previously recommended. Research indicates
and producer opinion confirms that deeper ponds have longer life expectancy and allow greater
water conservation. Where possible, ponds should be built to contain an average of 5.5 to 6 feet of water depth. This requires that average total pond depth with freeboard be 7 to 7.5 feet.
Minimum water depth in the shallow area should be 3.5 feet with a maximum depth near the drain of
8 feet. Ponds should have a minimum average water depth of 3 feet at all times. A bottom slope of
0.2 to 0.3 feet per 100 linear feet along the long axis of the pond is recommended for adequate
drainage.
In recent years, the average size of newly constructed, commercial catfish ponds has declined to 8 to 12 acres. As older, larger ponds (18 to 25 acres) have been renovated, producers have divided them into smaller production units. Fish farmers report that the additional costs associated with building smaller ponds are more than offset by improved feeding efficiencies and ease of management. A 12-acre land unit should yield 10 acres of water depending on levee top width and the slope selected for the inside levee.
Topography and the planned use for the pond will determine pond size. Ponds used to produce fry
and fingerlings are typically smaller than ponds used for food fish production. A typical layout
of commercial catfish ponds is shown in Figure 1.
Pond shape is determined by the boundaries of the production unit and the access to drainage. Ponds are typically rectangular and have a 2:1 to 3:1 ratio of length to width. While square ponds are cheaper to construct, rectangular ponds have the following advantages: longer levee length for feeding; lower electrical and piping costs; and shorter seines needed for harvesting (Fig. 1). A pond with a dimension of 500 x 1000 feet will contain approximately 10 acres of water.
Ponds should be as regularly shaped as possible. Triangular ponds or ponds with lots of curvature
in the levees can be difficult to harvest. These ponds are also more expensive to construct on a land to water-acre basis. Use remaining small or irregularly shaped parcels of land for feed
bins or equipment storage where possible.
The long axis of rectangular ponds should be parallel to prevailing winds during the peak
production period of April through October. Thus, ponds in the southeastern U.S. should be
constructed with the long axis running from west-southwest to east-northeast. A north-south orientation of the long axis should be avoided to minimize the erosion caused by winter winds.
Design of levees
Interior levees should have a minimum top width of 16 feet (20 feet is preferred so two vehicles can pass safely). Levees narrower than 16 feet may become difficult to traverse and be unusable in 3 to 5 years if there is even the smallest amount of erosion. Narrow levees hinder management
and are dangerous at night and when wet. Main access levees should have a minimum top width of 20 feet; 25 feet is preferred. Main levees must be wider to accommodate fixed equipment such as wells, generators, aerators and electrical panel boxes while permitting passage of feed delivery and hauling trucks. Main levees should be graveled for all-weather access. Harvesting, feeding and bird control are often carried out during wet conditions, making gravel essential on at least one side of each pond.
Freeboard is the height of the levee above the normal water level. A 1.5-foot freeboard height
is recommended (USDA Natural Resources Conservation Service) for a pond 600 to 1,300 feet long.
One foot of freeboard is adequate if ponds are less than 600 feet long. Excessive freeboard (more
than 2 feet) makes seining and placement of emergency aeration equipment more difficult.
Slope is expressed as the horizontal distance (in feet) that results in a 1-foot change in height. Hence, a 3:1 slope extends out 3 feet horizontally for each foot of height, and a 4:1 slope extends 4 feet horizontally for each foot of height (Fig. 2).
The slope selected by the pond owner will affect construction costs. Greater slope may decrease erosion but will also increase construction costs. For most soils, an outside levee slope of 3:1 is preferred. Inside slope
for commercial ponds typically ranges from 3:1 to 4:1 depending on owner preference. Slope
greater than 4:1 should be avoided, as construction costs are excessive and there are likely to
be more weed problems.
Figure 1. Layout of a typical levee-type catfish pond.
Drainage
A perimeter drainage system should be constructed to receive effluents and to prevent water
from standing outside levees. The existing drainage system might be modified, or a new system constructed. Earth removed during construction of the drainage ditches can be used as fill for levees. Drains are most often installed after the levee is constructed by trenching through the levee with a backhoe. This ensures proper placement of the drain and minimizes the risk of settling, which can hinder the complete draining of the pond. A single 10-inchdiameter drain of heavy gauge, coated metal or PVC pipe is adequate to maintain water level and drain a commercial pond. Because most soils have high clay content and most levees are relatively low, anti-seep collars are not usually included on the drainpipe. The drain should extend into the
pond and past the outside levee toe by at least 5 feet. A 1-inch drop in the pipe to the levee toe
will ensure complete drainage of the pipe when the pond is dry.
Figure 2. Cross-section of a typical levee for a commercial catfish pond.
Each linear foot of this levee contains 7.6 cubic feet of fill material.
The inside (pond side) drain end is capped with an expanded metal screen (0.5-inch mesh) 3 to 4 feet long to keep fish from entering the drain. If the pipe does not extend properly outside the pond, severe levee erosion is likely to occur when overflow or drain water is released. The outside end is fitted with a T standpipe to set the desired pond level and capped at the end with an alfalfa valve (Fig. 3). The length of the plastic terminal sleeve (or jam pipe or riser) can be altered to adjust the water level in the pond. Other drain types such as swivel pipes and concrete monks can be installed in commercial ponds but are not recommended because they cost more and have limited usefulness. The area immediately surrounding the interior drain (25-foot-radius) should be slightly deeper (3 to 4 inches) than the rest of the pond so that the pond drains fully. Any fish remaining at drawdown will be concentrated in this area.
Site preparation and construction
 Figure 3. Outside drain fitted with a T-stand pipe amd alfalfa valve. |
All vegetation, roots and stumps must be removed before levees are constructed. The top 2 to 3
inches of surface soil can be removed and reserved for placement on outside levee slopes so
that any recent pesticide residues are excluded from the pond. This soil will also be more conducive to establishing vegetative cover. Dirt pans are the primary implements recommended for commercial levee construction. They cost less to use and compact the soil better than other implements. Dirt pans lay down a thin layer of soil with each pass and pack the previously applied soil layer. Bulldozers are the primary implements used in pond renovation (see SRAC publication no. 104).
For proper compaction, soil moisture content should be 12 to 15 percent. Moisture levels higher or
lower than this can make soil compaction difficult. Levees built from heavy clay soils (more than
30 percent) following these guidelines should have a useful life of 10 years or more. Where groundwater is relatively abundant, wells are the preferred water source because groundwater
is free of undesirable fish and contaminants. A well output of 1,000 gallons per minute is considered adequate to fill and maintain 40 water acres (25 gallons per minute per water acre).
The well can be drilled either before or after construction. Well placement should be as close as possible to minimize the amount of pipe required. Lengthy pipe installations cost more to construct and repair, and yield less water because of frictional forces. The distance from the wellhead to the farthest discharge point should be less than 1,500 feet in any direction. Well pipes are buried in the ground to permit traffic on levee tops. Filling ponds by connecting pipes pond to pond is not recommended because it takes longer to fill connected ponds and disease
and trash fish can be transferred from one pond to another.
As soon as pond construction is completed, a vegetative cover should be established on the levees
to control erosion. Winter annuals such as rye or wheat or perennial forages such as bermudagrass make good cover and will exclude most volunteer grasses and weeds that provide poor coverage. If construction is completed and wheat or rye grass planted in the fall, it should be replaced with bermudagrass or another effective low cover in the spring. Establishing proper cover is cost-effective because it prevents excessive erosion, reduces mowing costs, and allows allweather
access to ponds. For information on the best ground covers for your location, consult your state Extension service Web site for publications or contact your county Extension agent.
References
PondsPlanning Design, Construction
United States Department of Agriculture/Natural Resources Conservation Service
Agriculture Handbook Number 50, Revised 1997
U.S. Department of Agriculture Washington, D.C. 20250
Commercial Fishponds
United States Department of Agriculture/Natural Resources Conservation Service
Conservation Practice Standard Field Office Technical Guide, Section IV, Revised 2000
U.S. Department of Agriculture Washington, D.C. 20250
Source: Southern Regional Agricultural Center and the Texas Aquaculture Extension Service - May 2002
