How Deep Should a Wildlife Pond Be?
Ponds have an increasingly important role in ensuring ecological connectivity and the survival of wildlife. Many natural water bodies have become lost or compromised due to urbanization and anthropogenic activity. Ponds in both urban and rural gardens have become a haven for both flora and fauna, as they require clean water to survive. They can support a biodiverse and self-sustaining community of fragile wildlife.
Unlike ornamental fish ponds, wildlife ponds are designed with potential pond visitors in mind. They should be welcoming instead of intimidating to critters that yearn for shelter and food. The features of the pond will determine the types of visitors it will attract. This is why depth becomes such an important factor for pond development. It dictates which keystone plants (primary producers) can survive in the water and eventually support a complex food web.
Wildlife Pond Depth Considerations
A pond’s water volume, as a function of depth, influences the rate at which its temperature, alkalinity, and hardness fluctuate. It also determines how much rainwater can be collected and replaced through the seasons. Depth determines whether the pond can persist through summer, as evaporation rates increase, and through winter, when low temperatures can cause water to freeze over.
The deeper a pond, the more likely depth can serve as a buffer to maintain stable parameters. It also opens up layers in the water column with differing conditions to suit a wider variety of plants and animals. That being said, there’s no single depth that would suit wildlife ponds in all types of environments. The depth of a wildlife pond should be decided upon with your goals and your climate conditions in mind.
For example, if you live in a temperate zone that experiences negative temperatures through winter, you’ll want your pond to be at least 60 cm (2 feet) deep. This ensures that the deeper parts of the water column can remain liquid through winter and should stay relatively cool in warm summers. Larvae, small fish, and young amphibians should be able to survive through weather extremes in a pond of this depth.
If you would like to attract larger animals (waterfowl, reptiles, and semi-aquatic mammals) or cultivate submerged flora with tall shoots, you may consider increasing the depth. Don’t forget that enough light and oxygen should reach the pond bottom to ensure that benthic communities are able to survive and provide their ecological services.
Can a Wildlife Pond Be Too Shallow?
At the end of the day, any water depth will benefit wildlife that are in need of hydration. But, to make your pond building efforts more worthwhile, your pond should be no less than 12 inches (1 foot) deep. A shallow depth would actually be quite convenient as you can simply put on a pair of wellies to venture into your pond and do some tidying up.
Shallow ponds that are naturalized well (i.e. artificial materials are disguised by plants and organic finishing touches) will attract many small animals, particularly those that require water to lay their eggs and survive through the major stages of their life cycles. In turn, these may attract potential predators. Larger predators are less likely to seek shelter from shallow ponds, but they may visit frequently to feed on the assortment of prey items. To provide permanent shelter for these predators, your pond will likely need to be larger and have more complex edge features.
Importance of a Depth Gradient
The most effective wildlife ponds are those with varying depths. A depth gradient can open up many ecological niches for visitors to fill, enhancing the natural profile of the pond. The borders should be shallow and gradually slope towards the deeper area. This facilitates better movement of plants and animals from the periphery of the pond to the deeper areas.
Shallow shelves and trenches located throughout the pond’s circumference may be the most abundant areas of your pond as these tend to have the highest light and oxygen levels! Basking animals and aquatic insects are likely to stay in these areas and lay their eggs in accessible vegetation. Marginal plants will surely thrive in these shelves and provide shelter to animals. When selecting plants, keep in mind that frequent or heavy rains may increase the water level in these areas.
A gradual slope along one side of the pond can facilitate ease of entry and exit for amphibians like turtles and salamanders. A gentle 4:1 (extending 4 feet for every foot of depth) slope ratio would be best as this mimics the shoreline of many natural water features. This means that a deeper pond will require a much wider surface area. If the pond is small but deep, a steep drop from the edge would hinder visitors from moving in and out of the pond.
Creative Ways to Vary Pond Depth
A shallow shelf followed by increasingly deeper platforms following the pond’s outline is a typical design incorporating varied depths. When digging out the pond, try to visualize how you would like to arrange your pond features. It helps to pinpoint the specific animals you wish to attract and determine how they may easily navigate around the pond.
Unlike ornamental fish ponds, wildlife ponds need not have unobstructed horizontal space through which large fish may swim. You can instead create many levels throughout the pond. You can even opt to have shallow areas closer to the center of your pond as these may serve as resting or perching areas for frogs, turtles, and waterfowl. You can make use of logs, boulders, submerged pots, recycled pipes piled on top of one another, or even old bathtubs and sinks. The possibilities are truly endless!
How to Naturalize a Deep Pond Bottom
The best way to mimic the benthic environment of naturally deep ponds is with the use of submerged oxygenators. These will help maintain a well-balanced pond bottom via nutrient assimilation, oxygen production, and the provision of shelter to bottom dwellers. The foliage of submerged plants also increases the surface area on which beneficial bacteria and algal communities may grow. The growth of these oxygen-dependent microbes will then foster larval communities.
The submerged plants that you choose should ideally be native to your area, especially if they have the means to spread by fragmentation or rhizomatous growth. Floating plants that produce lengthy shoots or roots extending to the pond bottom may be cultivated in the deeper areas as well. These should help limit algal growth and regulate pond water temperatures. For a list of plant suggestions for wildlife ponds, consult this article.
Dangers of Deep Wildlife Ponds
Like all considerably-sized bodies of water, wildlife ponds come with their own dangers. It’s important to be aware of them in order to prevent potential accidents. Nevertheless, don’t let these dangers dissuade you from cultivating your own diverse pond as it can ultimately be beneficial to your local ecosystem.
It is important to be wary of the wild animals that your pond may attract. Generally, allow them to keep to themselves. Avoid disturbing their forms of shelter or touching them unless absolutely necessary. They may carry parasites and diseases that can be passed on through contact.
More importantly, always monitor young children who veer close to the pond. It is, without a doubt, a great place for them to learn about wildlife, but accidents may occur without the watchful eye of an adult. Keep in mind that unsupervised children have drowned in deep garden ponds. Moreover, it can be impossible to tell what lurks in turbid pond water. Snakes and other stealthy predators may also be hiding in the water or surrounding vegetation.
Lastly, the bottom layer of deep stagnant water may be depleted of oxygen levels, creating pockets of sulfur in the sediment. Stagnant water may also become breeding grounds for mosquitoes and parasites. It may help to add a pump or moving water feature in your pond to stimulate the movement of water and distribution of oxygen.