Water and flood-tolerant plants are one of the best tools for building a retention pond that effectively processes storm water and enriches the local environment. While encouraging plants to grow in and around the water will increase maintenance slightly, the benefits of the vegetation will be well worth the effort. Instead of using harmful herbicides to try and keep a concrete pond bare and clean, consider a planted design for the following benefits.
Plants are very important for retention ponds that intended to treat and improve water quality. In addition to storing water for slow release, plants are also vital for pollution absorption. Excess nutrients in the water like nitrogen and phosphorous are directly absorbed by the roots of the right plants in and around the pond. This leads to lush growth that further boosts the water quality. For chemical and bacterial pollutants, the bacteria that live on the roots and stems of the water plants do most of the heavy lifting. Without natural growth mediums for hosting these bacterial colonies, retention ponds tend to stagnate and do little to improve water quality in the long run. A well-planted retention pond will discharge clearer, cleaner, better smelling water into nearby waterways and underground water tables.
Absorption of Nitrogen
Nitrogen, in particular, is common in retention ponds and likely to cause problems. High levels of dissolved nitrogen lead to algae growth, which clogs the drainage systems of the pond and increases the chances of an overflow. Algae-filled retention ponds also tend to turn anaerobic due to a lack of oxygen in the water. This creates unpleasant odors that may upset residents and business owners around the water feature. If the nitrogen remains in the discharged water, algae blooms will spread to other natural water features. These blooms dramatically reduce oxygen and can kill off fish populations.
It’s difficult to keep nitrogen levels under control with chemical treatments alone, especially when there’s a constant source from nearby agricultural or livestock fields. Manure runoff from cows and chickens is one of the most common reasons for high nitrogen levels in a rural retention pond, while urban features may accumulate fertilizer runoff from parks and landscaping features. Water and edge plants are your best option for naturally controlling high nutrient levels across the board, including nitrogen.
Habitat for Fish and Wildlife
Planted ponds also attract other forms of life that enrich the man-made environment. Fish are a smart addition to any retention pond where water quality is relatively high throughout the year. A light stocking rate will control mosquito and insect issues. Other wildlife will be attracted to a healthy and well-planted pond, including waterfowl, small mammals, and even large mammals like deer and moose. Domesticated ducks and wild geese may become a nuisance as they leave droppings and lay eggs around the pond, but other birds like cranes and wood ducks aren’t messy and should be left alone.
Concrete ponds aren’t attractive to wildlife because of the lack of cover and protection around the edges of the water. Without plants to disguise them, most birds and large mammals will stay away unless it’s the dead of night. Concrete banks are also slippery and increase the likelihood of an animal getting injured or trapped in the pond, while planted banks provide better footing. Unless you need to discourage animal access as much as possible and plan to fence off the pond, try to stick with a planted design rather than a bare concrete surround.
It’s essential to keep a retention pond looking its best when the water feature is highly visible. When it’s the centerpiece of a planned community or neighborhood, letting weeds and invasive plants settle in will lead to an unattractive pond. Careful selection of native plants, with desired growth habits, will eliminate or reduce the need for manual or chemical control. A well-planted pond full of appropriate species won’t become clogged with invasive weeds as easily due to the established competition. Planted ponds still need routine cleaning and maintenance to remove overgrowth, but this is much more pleasant than trying to remove tenacious water weeds that keep moving in every few months to a bare pond.
Liners for Planted Ponds
Despite having a natural bottom layer of mud and soil for plants to root in, planted retention ponds work best when lined with a geomembrane. Materials like RPE are easily buried to create an impermeable barrier below the soil for the plants. This prevents seepage and stabilizes the ground around the pond while still allowing for natural and healthy growth in the water. Make sure to choose plant-safe materials and fish-safe liners if you want to add fish. Not all pond liners are safe for fish and plant use, even when they’re completely buried.
Lining your planted retention pond allows for strong root growth of your chosen plants while keeping aquatic weeds from getting a grip in the soil. When maintenance is needed, it’s much easier to remove extra plants since they can only grow so deep before hitting a solid barrier. Choose a product like BTL Liners AquaArmor for a retention pond liner that won’t hurt any fish or plants you plan to add to the water.