Ohio Pond Management
Proper planning and construction are the keys to building a pond that will meet owner needs whether they are primarily recreational, aesthetic, or agricultural. Prospective pond owners should obtain technical advice from government agencies for guidance concerning pond design. These agencies offer the necessary experience to recommend the pond size, depth, location, and dam and spillway construction that are best suited to the landowner’s desires and the watershed and soil characteristics.
On-site advice from natural resource professionals is the first step for building a pond that will provide years of satisfaction and require minimal maintenance. Prospective pond builders should seek advice from the USDA Natural Resource Conservation Service. Their agents provide help with soil surveys, site selection, pond design and construction. Further assistance may also be obtained from your county Soil and Water Conservation District (SWCD) and local office of The Ohio State University Extension Service
Watershed. The entire land area that drains into a pond is called the watershed. A landowner needs to consider the size, use, ownership and slope of this drainage basin before building a pond because ponds receive most of their water from surface runoff, rainfall and groundwater. These factors may limit the size and type of the pond that is practical to build. Generally, a one acre pond should have a 10- to 15-acre watershed, or approximately three to five acres of drainage area for each acre-foot of water storage. If the drainage area is too large, large and expensive spillway structures must be built to prevent the dam from washing out when large inflows of water follow heavy storms. Too much inflow may also cause sedimentation and other water quality problems. On the other hand, if the watershed is too small for a pond’s capacity, then proper water levels may not be maintained during droughts. The pond’s water level should not fluctuate more than two feet during drought conditions. Groundwater should make up for losses from evaporation and normal seepage of water through the pond bottom. Achieving the proper watershed size to pond size ratio is one reason that technical guidance is important in building a pond.
Land use practices on the watershed will also affect water quality in a pond. Significant industrial, pesticide, acid mine drainage, or septic pollution sources on the watershed should be corrected before pond construction, or an alternative pond site should be chosen. Drainages with high agricultural land use should be avoided if possible. Forested or non-agricultural grassland watersheds provide the best protection against sedimentation and water quality problems.
Soil. A landowner needs to identify the type of soil at the prospective pond location during the planning and design process. Soil type is important to consider when selecting a pond site because the capabilities of soil to hold water differ between soil types. Soils must contain at least 20 percent clay by weight to prevent excess seepage. When clay soils absorb water they swell and seal the bottom of the pond. Three feet of high clay content soil is usually needed below the excavation level to prevent excess seepage. If porous soils such as sand and gravel underlie the pond basin, then either an alternative site must be considered, or an impervious layer of soil should be compacted over these areas to prevent excess seepage or leaks. If only a small portion of the pond basin has undesirable soils, it may be possible to haul in good clay soil from a nearby area without significantly increasing construction costs. Although county soil survey maps can be very useful for determining the type of soils present and their suitability for a pond, thorough site investigation is essential prior to construction. Call your local Natural Resource Conservation Service agent for information on soil test pits and soil type testing.
Pond Size, Depth and Location. Pond size and depth may be dictated by the intended uses of the pond. Ponds designed for sportfishing should not be smaller than one surface acre because smaller ponds tend to be more difficult to manage. Large ponds are generally more cost effective to build and offer better and more sustainable fishing. A minimum depth of eight feet or more should be maintained in at least 25 percent of the pond basin. Deeper water may be necessary in the extreme northern part of Ohio where winter snow and ice may prevail for long periods of time. Greater volume and depth may be required to prevent of a winter fish kill. In such cases, 10 to 12 foot depths should be maintained in at least 25 percent of the pond basin. However, ponds constructed with depths much over 12 feet are often a waste of money for they create no additional benefits to fish.
Local soil conditions may also dictate the exact depth that can be achievedwithin these recommended ranges. Shoreline areas should be constructed with slopes adequate to prevent excessive growth of aquatic vegetation, yet provide quality fishing. A slope that drops one foot in depth for every three feet of distance towards the center of the pond, or a 3:1 slope, should be maintained along most of the shoreline areas. This will create the best conditions for spawning areas, provide cover and feeding areas for largemouth bass and bluegills, and minimize pond maintenance. Extensive areas of water less than three feet deep often become choked with aquatic vegetation and algae. Prospective pond owners also need to consider pond location in their planning. Convenient access for recreation and maintenance is important to most pond owners. Others, however, may want to locate their ponds where more privacy is provided.
Dam Construction. A dam should be located where it is least expensive to build. Construction costs can be minimized by selecting a site that requires minimal soil movement and easy access to construction equipment. Keeping the length and size of the dam at a minimum will also reduce costs. Sites which have steep to moderately sloping terrain, tapering off to a relatively level basin are best for embankment ponds. Excavated ponds are preferred over embankment ponds in flat or gently sloping terrain and may not require an expensive dam. Floodplains should be not be selected as sites for either type of pond because the dam may be eroded by floods.
Dams should be designed and constructed by experienced professionals to ensure reliable service. Improperly installed dams present safety hazards and are an economic liability to the landowner if a dam fails. Properly designed, constructed, and maintained dams help stabilize water levels during periods of heavy rain, minimize loss of water during drought, and permit pond draining. The exposed slopes of the dam should be graded with topsoil and seeded immediately with a combination of perennial grasses to prevent soil erosion. If the dam is completed in the fall, annual rye grass, wheat, or oats should be planted to provide erosion protection until spring when the area can be reseeded with perennial grasses. Regular mowing and maintenance are necessary to prevent trees from growing on the dam. This is important because tree root systems may cause leakage problems and attract burrowing animals. Rock riprap can be added to the slope on the water side of the dam to further prevent erosion and burrowing by nuisance animals.
Figure 1.2. Pond types: excavated, embankment, combination.
Excavated Ponds. Dug or excavated ponds are constructed in areas of flat or gently sloping land not suited for ponds with dams. As the name implies, dug ponds are created by removing soil and allowing water to fill in the dug out area. Most of the water supply comes from ground water seepage or natural springs. Soils are usually made up of materials that allow free movement of water through the pond bottom.
Embankment Ponds. Embankment ponds are more common in areas with moderate to steep sloping terrain. They are created by building a dam between two hillsides to collect and hold water from overland runoff. The pond bottom and dam must be made up of soil that prevents excess seepage. Embankment ponds should not be built by damming permanent flow streams, no matter what size they are. Small streams are a source for silt, sediment, debris, excess nutrients, and undesirable fish, all of which can degrade water quality and reduce chances for good fishing.
Combination. In many instances, a combination of digging and impounding (damming) is used to create a pond. A dam is built to hold water and some digging is used to finish the basin to the desired slope and depth.
Spillways. The principal spillway (pictured) is usually located along the face of the dam at the normal water level. It is designed to maintain the water level under normal inflows from snow melt, spring flow, and rain. Drop inlet and hooded inlet trickle tubes are two of the more common overflow pipes used in farm ponds. Hood inlet tubes pass at an angle through the center of the dam and drop inlets pass underneath the dam. Drop inlets are more expensive to install than hooded inlets, but can be designed to allow the pond to be drained. This is an important feature to have in ponds managed for fishing. All pipes that pass through the dam must be installed with anti-seep collars to prevent leaks from developing along the pipe as it passes through the dam.
Embankment ponds should have both a principal and emergency spillway. The emergency
spillway provides an exit point for excess water. During periods of high rainfall, it routes water around the dam to prevent excess storm runoff from flowing over and eroding the dam. The emergency spillway should be cut into undisturbed terrain adjacent to one end of the dam where the overflow will fall into the natural drainage.
Drain Pipe. When possible, a drain pipe should be installed in ponds managed for fishing. This allows the pond to be drained to eliminate undesirable fish populations, or drawn down for management of nuisance aquatic plants, maintenance of banks, or repair of the dam. A drain pipe may also facilitate livestock watering (see concerns about livestock and pond construction).
Dry Hydrants. (pictured) Dry hydrants can be installed in just about any pond as a readily available source of water for fire fighters. This is an especially nice feature in rural areas that lack public water supplies. Dry hydrants can be installed into new or old ponds, but are usually more convenient to install during construction. Personnel from the county Natural Resource Conservation Service office can provide material specifications and construction and cost information for installing dry hydrants.