Ponds in South Carolina

Four types of ponds are common in South Carolina; these include aquaculture, irrigation, recreational, and stormwater ponds. Pond type influences the practices used to manage water quality, water quantity, and aquatic biodiversity. This article provides introductory information to producers, landowners, municipalities, homeowners associations, housing and commercial property developers and managers, golf course managers, and pond managers related to pond type, design, regulations, and pond health.

Ponds are small (10 square feet to 12 acres in surface area) shallow waterbodies (at minimum 3 feet deep) that hold water all or for a majority of the year.¹ Ponds in the coastal region of South Carolina are typically 4 to 6 feet deep.² Ponds in the sandhills and piedmont regions of South Carolina are typically 4 to 9 feet deep, and the permanent pool depth should not exceed 20 feet.³ The SC Department of Natural Resources (SCDNR) estimated there were 50,000 or more ponds in South Carolina in 2009.² A 2013 survey counted 21,594 ponds in aerial imagery from eight coastal South Carolina counties.⁴ Ponds typically serve as water sources (livestock drinking water, irrigation, and recreation) and as a means to capture and control stormwater. Streams and wetlands are the natural means by which stormwater moves into groundwater and to the ocean.

Regulations and Ponds

Essentially all surface waters, their tributaries, and adjacent wetlands are considered Waters of the United States, and permits may be required for modifications or changes impacting them.⁵ Please refer to the “How the 2020 Definition of WOTUS Affects Agricultural and Specialty Crop Producers” publication (bit.ly/3jsBxDW) for more information on identifying surface waters that constitute Waters of the United States.⁶ Exceptions may include stormwater ponds, qualifying agricultural irrigation ponds, and small features that do not connect with Waters of the United States (e.g., ephemeral streams). The USDA Natural Resource Conservation Service (NRCS) often assists agricultural producers in determining if a proposed activity qualifies under an agricultural exemption.⁷

Permits, including but not limited to the following, may be required prior to actions affecting Waters of the United States:

• Modifications/Impacts may require a series of permits, including a Section 404 permit (bit.ly/3x7cSsx) from the US Army Corps of Engineers and a Section 401 Water Quality Certification from SC Department of Health & Environmental Control (SCDHEC).⁸
• Surface Water Withdrawal (≥3MG in any month) requires either a Permit or Registration (for qualifying agricultural producers) from SCDHEC.⁹
• Groundwater Withdrawal (≥3MG in any month) requires either a Permit (if within a Capacity Use Area) or a Registration (if outside of a Capacity Use Area) from SCDHEC.¹⁰
• Discharges associated with wastewater, industrial, or construction activity may require an NPDES permit from SCDHEC.¹¹
• South Carolina’s Water Quality Standards,¹² which apply to surface and groundwater, are overseen by SCDHEC. Some standards vary by ecoregion, water classification, as well as waterbody type and size.
• Throughout South Carolina, a stormwater permit and best management practices are typically required for construction sites of ≥1 acre.¹³ Specific requirements may vary based on city or county regulations.

Under the South Carolina 1977 Dam and Reservoir Safety Act, any dam which exceeds 25 feet high will impound more than 50 acre-foot of water (approximately 10 acres x 5 feet depth), or that could result in the loss of life in the case of failure needs to be permitted.¹⁴ Currently, there are 2,300 registered dams due to size, location, or proximity to human dwellings that are regulated by SCDHEC.¹⁵ SCDHEC estimates that there are over 20,000 unregistered dams in South Carolina.¹²

For help determining if a permit is required, agricultural users in South Carolina can further read about permitting requirements specific to agricultural water in the “Water Withdrawal Regulations Every Agricultural User in South Carolina Should Know” publication (bit.ly/3dvBKm4).¹⁶

Pond Design

While pond design ultimately depends on pond type, most ponds generally share some common components, including inlet and outlet structures, emergency spillways, and underlying soils. Some ponds are designed with a forebay (storage space close to the inlet to settle out coarse sediments), which protects the storage capacity of the pond, and provides easier access for targeted dredging. The depth of the pond can depend on the intended use, such as irrigation, water storage needs, or limited by water table depth.

Types of Ponds

Aquaculture

Aquaculture ponds are designed and operated to produce finfish or other aquatic species. These ponds can be irregularly shaped (watershed ponds) or designed with rigid facets (levee ponds).¹⁷ Watershed ponds are standard if ample amounts of high-quality surface runoff water and rainwater keep the pond full. Conversely, levee ponds seem to be more popular and maintain water levels with groundwater or sub-surface water sources.¹⁷ Careful consideration is needed to construct a functional aquaculture pond. Some site characteristics to consider include the soil type for water retention, source water quality, access to utilities (electricity), and access roads. The more common levee ponds are usually rectangular, located in flat areas, and contain embankments to restrict water movement out of the pond. The levees are built wide enough to handle vehicle traffic to feed and harvest the fish with ease and include a slope of 3:1 for safety measures and to minimize the cost associated with pond construction. Levee slope is expressed as the horizontal distance (in feet), resulting in a 1-foot change in height. Hence, a 3:1 slope extends out three feet horizontally for each foot of height.¹⁸ Water quality is critical in aquaculture ponds. It is essential to determine the availability of good quality water before investing in aquaculture production.¹⁹

Irrigation: Livestock and Plants

The number of farm (irrigation) ponds in the United States increases by 3% to 4% each year.²⁰ Irrigation ponds serve as a water source for livestock and plants (figure 1) and as a primary or backup water source, depending upon producer preference and water availability. Irrigation ponds also provide ecological services within the landscape, including capturing storm runoff, slowing velocity of surface runoff, capturing sediment, and slowing nutrient movement through the aquatic ecosystem.²⁰

Livestock Ponds

Whether using an existing pond or planning to build a new pond for livestock watering, several factors should be considered to determine long-term suitability. First, determine if the supply of water is enough for your expected number of animals. Other factors to consider when planning the construction of a new pond include slope, size of the watershed, average rainfall, soil type, and the acreage and depth of the pond.²¹

Restrict livestock from drinking directly out of the pond to protect animal health²² and water quality.²³ Protecting water quality preserves clean water for livestock use and supports healthy aquatic communities (from invertebrates to fish) and wildlife populations while protecting downstream water quality for other users.²⁴ Common water quality issues with an open pond for watering livestock relate to the added nutrients and bacteria from animal waste and increased sediment entering the pond due to erosion caused by the livestock entering and exiting the pond. Ideally, livestock are completely fenced out of the pond, and water from the pond is directed or pumped into troughs.

Various designs can be employed to route water from the pond into drinking troughs, including gravity flow systems or powered systems using energy from electrical, solar-charged battery, or hydraulic sources.^25,26 In some circumstances, allowing limited access to the pond for drinking can be successful if a ramp with gravel is constructed to minimize erosion and the environmental impact is minimal.²⁷ Other considerations for protecting pond water quality include best management practices of the upland pastures, including proper stocking densities, maintenance of optimal residual forage cover, buffer strips, and avoiding the use of pastures near a pond’s edge during wet periods.²⁸

Figure 1. Irrigation pond with concrete spillways around the pond’s edge to permit controlled water entry. Image credit: Sarah A. White, Clemson University.

Plants

In terms of crop production, adequate water availability and contaminant presence are of concern. Ponds can serve as a backup or primary source of water depending upon the locale within South Carolina. In some instances, ponds are filled using well water because the well flow rate (gallons per minute available) is inadequate to meet irrigation demand. Often, a producer can fill a pond with well water over time (typically a 24-hour period) and capture adequate water for irrigation. In the Piedmont ecoregion, well and surface waters are used in similar ratios; in the Southeastern Plains (Sandhills) ecoregion, well water is the primary water source, whereas, in the Coastal Plain ecoregion, ponds are the primary water source.²⁹ Generally, row crop and specialty crop producers are concerned about the presence of disease-causing organisms, weed seeds, and pesticide residues in irrigation water.³⁰ Most plant producers, unless growing intensively indoors, do not treat surface waters prior to use, so there is potential for contaminants present in pond water to reduce crop growth or yields. The pH of water in farm ponds also changes daily, as aquatic plants and algae present in the water absorb or release carbon dioxide as they respire and photosynthesize.³¹ Depending upon the crop grown, substrate (mineral or soilless substrate), or use (pesticide spray mix water), water treatment may be needed prior to safe use.

Recreational

Recreational ponds are typically created by impounding a stream or excavating until groundwater is reached to provide a visual amenity and support fishing, swimming, wildlife/bird watching, waterfowl hunting, or a combination thereof (figure 2). In addition to streamflow or groundwater seeps, water may also be supplied by surface runoff from surrounding land. The chemistry of the source water flowing into the pond can influence the pond’s health. The quality of water leaving a recreational pond will impact the health of downstream water bodies. Both groundwater exchange and surface runoff may transport contaminants (nutrients and sediment) from surrounding areas into nearby waterways.³² Excess nutrients entering recreational ponds can cause concern for pond owners as they support excessive aquatic plant growth and sedimentation reduces the pond’s water storage capacity. Taking action to reduce the mass of contaminants in surface runoff entering recreational ponds can help protect their long-term health. Actions could include not mowing to the edge of the pond, limiting fertilizer applications within twenty-five feet of the pond edge, leaving vegetation (buffer strips) around the edge of the pond, and planting the edge of the pond with aquatic plant species.

Figure 2. A recreational pond with trees along much of the shoreline. Image credit: Adam Gore, Clemson University.

Stormwater

As population centers have expanded in South Carolina, streams and wetlands have been lost to development while impervious surface areas (e.g., roads, rooftops, etc.) have increased.² Stormwater ponds are now commonly integrated within new developments to meet flood control and water quality requirements. Stormwater ponds, or detention basins, are widespread across South Carolina and installed as best management practices (BMPs) to manage runoff generated by impervious surfaces and comply with stormwater control requirements (figure 3). Historically, stormwater ponds were designed to manage localized flooding from stormwater runoff. However, due to more recent state and local stormwater regulations, stormwater ponds are increasingly designed to treat water quality, providing benefits such as sediment retention and nutrient removal.

Figure 3. A stormwater pond in coastal South Carolina. Image credit: Sarah A. White, Clemson University.

Ponds can be classified as wet or dry, depending on their typical state.

• Wet ponds are designed with a permanent pool of water, which could be used for irrigation or to increase the retention time of water in the pond for water quality treatment before discharged downstream. Wet stormwater ponds often provide additional ecosystem services, such as carbon sequestration, fish and wildlife habitat, recreational opportunities, and aesthetic beauty, in addition to the flood control and water quality services they are designed to provide.³² Yet wet ponds are designed to trap contaminants (e.g., heavy metals), so swimming and eating fish caught in the ponds is unwise.
• Dry ponds provide temporary storage of stormwater during storms and may also provide water quality benefits.

Competing uses created by the additional services (e.g., fishing and recreation) can create misperceptions among stormwater pond owners regarding the stormwater pond’s primary purpose, which can then influence the management of these systems.³³

Proper maintenance is important for the long-term functioning of the pond. Over time, sediment can accumulate in the pond, reducing overall storage capacity. Sediment and erosion control practices upstream can help reduce sediment input to the pond, as can stabilization of pond banks through the use of vegetative buffers. Older ponds will likely need to be dredged to remove excess sediment. Permits or testing may be required for dredging or disposing of dredged materials. The input of nutrients to the pond can stimulate algal blooms, typically starting in early summer and continuing through fall, and contribute to the growth of aquatic invasive plants and poor water quality.³⁴ Some algae growth is to be expected during the summer months simply because conditions are optimal for algal growth. Managing nutrient use on the surrounding landscape can help to reduce nutrient input to the pond and limit how extensive an algal bloom can become. Regular maintenance can also include litter removal to maintain flow at the inlets and outlets, aeration, upland management, and other actions.

Figure 4. A small pond with algae problems likely caused by nutrient-rich surface runoff. Image credit: Sarah A. White, Clemson University.

Assessing Pond Health

To maintain the intended purposes of a pond, it is important to periodically assess the health and performance of the pond. Evaluate pond health at least once per year (ideally in June, when algal issues are to likely become noticeable). Visual observations can help you gain a high-level assessment of pond health (figure 4). Are there dead fish, algal mats, murky water during dry periods, or nuisance smells? This could indicate the ecological health of the pond is out of balance. If you note any of these symptoms, it is wise to collect a water sample from the pond so you can quantitatively evaluate water quality (e.g., Chlorophyll-a (a proxy for algae presence), total phosphorus, total nitrogen, and turbidity).

Results from a water quality test can be compared to plant and soil health standards or SCDHEC surface water standards to assess potential problems.^12,35 Elevated internal contaminant concentrations (e.g., chlorophyll, turbidity, nutrients, E. coli) may be of concern, depending upon pond type and intended use. Yet, elevated concentrations of a specific contaminant could indicate the pond is functioning as intended within the landscape and is helping reduce contaminant loads before they reach surface waters. If you compare sample results with water standards and note elevated contaminant presence in contrast with water quality standards, it may be an opportunity to evaluate your pond management strategies to reduce contaminants entering the pond from upland landscapes. You can learn more about collecting a water sample and some of the contaminants of concern for agricultural ponds in the “Collecting Samples for Agricultural Irrigation Water Quality Testing” publication (bit.ly/3yfMrBd).³⁶ If algae are present, you can collect a water sample both for chemical analysis (what nutrients are present) and to identify the species of algae to determine if the algae you see is cyanobacteria and potentially a harmful algal bloom.³⁷ The Clemson University Plant and Pest Diagnostic Clinic /) typically returns algae sample results within five business days. Visit the website for additional information (clemson.edu/public/regulatory/plant-problem).

How Ponds Influence South Carolina Waterways

Generally, ponds are designed to fulfill a specific purpose within the landscape. Yet uses of a pond may exceed its intended use, expanding to mitigation of nonpoint source pollution, reduced channel erosion, support of ecosystem function, and groundwater recharge (larger ponds).²⁰ In comparison to large lakes, ponds are also biodiversity hotspots that help to link existing aquatic habitats.³⁸ Ponds provide freshwater habitat for many species of insects, aquatic invertebrates, fish, amphibians, reptiles, aquatic birds, mammals, and plants. However, impacts from impoundments are one of the challenges to conserving native aquatic fauna.³⁹ Other biodiversity hotspots in the landscape like wetlands and free-flowing streams provide habitat for many native and endangered species, and these should be considered when determining where to locate a pond.

Ponds can serve as a best management practice that is part of a larger treatment train. A series of ponds or ponds with best practices in upland management and buffer strips may improve water quality before the water exits the pond and enters other surface waters.³³ Conversely, ponds can also negatively influence water quality downstream, so proper design, management, and maintenance are critical.^40,41 Depending upon the purpose of the pond, alternate design strategies and management practices can be applied. For those interested in detailed knowledge of ponds, Clemson Cooperative Extension offers the Master Pond Manager course. Information is available on the course website (bit.ly/2UmL3hy). If you have additional questions, please consult with the Clemson Cooperative Extension Agent at your county Extension office, NRCS Agents, or respective agencies as directed throughout this article regarding permitting, water quality, or design.

Additional Resources

Stormwater Pond Design, Construction, and Sedimentation, Clemson Cooperative Extension Webpage (bit.ly/3hb04vR)

Pond Construction and Tax Credits, USDA NRCS PowerPoint Presentation (bit.ly/3AmAfQY)

Aquatic Garden Pond and Pool Construction, Clemson Cooperative Extension, Home & Garden Information Center Factsheet (bit.ly/3xcRbaB)

Ponds – Planning, Design, Construction, USDA NRCS Agriculture Handbook Number 590 (bit.ly/3wgrxAd)

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