Apart from natural rainfall, the most common source of water for most of our gardens is either municipal water supplied via a garden faucet or reclaimed water from a rain barrel. But there are other sources including wells, streams, and ponds. The question, though, is how safe is pond water for vegetables?
Pond water is generally rich in nutrients. It contains nitrogen and phosphorus, both of which are essential for good plant growth. This is why it is sometimes called fertile water. But it can also be a source of pathogens that can harm your plants. If your pond is healthy, it is probably safe for watering vegetables.
Things to consider when using pond water for vegetables
Any water you use to irrigate a vegetable garden needs to be safe. Harmful pathogens include salmonella and E. Coli, both of which thrive in water.
So what are the best sources of water for your vegetable garden?
Best Sources of Water for Vegetables
Unfortunately, as Karen Filchak, an extension educator from the Unversity of Connecticut’s College of Agriculture, Health, and Natural Resources points out, some water sources can contaminate your vegetables.
Municipal water is treated and monitored for contaminants, so it is generally safe. But she recommends that if you use rain barrel water, pond water, or private well water to water plants, you should have it tested.
Additionally, her belief is that groundwater is a lot less likely to be contaminated than surface water.
The most reliable method of testing is to take a water sample to a laboratory. But there are also many test kits available that will give you a good idea of water quality very quickly.
While groundwater comes from wells, surface water is generally found in ponds and streams. Filchak warns that while rain barrels have become popular, there hasn’t been a lot of research regarding microbiological contamination from this water source.
But it’s not that simple because if you are planning to use the water from your garden pond for irrigation, you may be filling your pond with a municipal water supply! In this case, your pond may provide you with safe water for your vegetable garden.
Also, as she says, there are currently no universally accepted standards for water used to irrigate fruit and vegetables. So, it’s a bit of a conundrum.
The University of Georgia Extension has a useful publication on sources of water for the garden. Their preference is rainwater, although they acknowledge that we almost always need to supplement water somehow.
While ponds are a definite supplemental option, a practical consideration this publication raises is the need to pump water from sources like ponds, rivers, and creeks. Also, while rivers and creeks usually have free-flowing water, it is more likely for pond water to contain a build-up of algae.
Where does pond water come from?
Another vital question, which we’ve already touched on, is where pond water comes from. This will likely determine the advantages and/or risks of using this water for vegetables.
A primary difference is that some ponds are manmade and others are natural. While you will usually have more control over the quality of water in manmade ponds, this is not always the case.
Apart from municipal water safe for plants, ponds fed with spring water provide a safe source too. The same applies to any type of water garden that relies on rainwater to keep it wet.
But ponds designed for retention or detention may not provide safe use water for pond water plants or your veggies. This type of pond will often be filled with water that runs off streets or other areas that contain contaminants.
Another caveat is that runoff water may contain wastewater. There are lots of potential pollutants including industrial effluent and sewage, depending on where you live.
If you have a garden pond that is safe for fish, you will need to focus on routine maintenance, especially if it’s a koi pond. You will want to recirculate and filter the water, adding fresh, clean water from time to time.
More often than not, the water you use from this type of pond water will be absolutely safe for your garden, including fruit and vegetables.
The other factor to be aware of when creating your own garden pond is the possibility of contamination from pond liners. Some materials, including PVC intended for tarps and roof liners, often contain toxic plasticizers.
Generally, if you choose products that are pond safe, they will be fish and plant safe. To be sure, check with the manufacturer.
Advantages of using pond water for vegetables
The minerals and nutrients found in most garden fish ponds will benefit your vegetables. Generally, the more fish you keep, the higher the nutrient content will be.
These nutrients are excellent organic fertilizers for vegetables. This so-called “fertile water” provides nourishment and the water needed for plant growth.
In essence, when pond water is fertile and clean, it will increase your veggie productivity. It is also an eco-friendly, inexpensive solution for fertilization.
Risks of using pond water for vegetables
While the water fish live in contains high concentrations of nitrogen (which is a good thing for vegetable gardens), the waste build-up from fish contains nitrites and ammonia. These compounds can be toxic to fish and may not be beneficial to plants unless you ensure you aerate and filter the water sufficiently.
Safe pond water is clean. But when it contains toxic pathogens it isn’t clean, and it’s better not to water plants with it … especially vegetables.
Remember that the more fish there are in ponds, the higher the nutrient content will be. Like all things in life, too much of a good thing can be detrimental!
A healthy garden or community pond will usually be safe for watering vegetables. You do, though, need to be aware of the potential risks of using pond water.
If you’re not sure, it’s best to test the water, at the very least to determine whether the pH levels are suitable for fish and your plants.