Regularly cleaned, water tanks are a sure way to provide safe water for your horse.

The idea of a pond to provide a constant water supply to your horses is appealing, but it might not be what we consider clean or safe. Obviously feral horses drink from ponds, lakes and streams, but that doesn’t mean they never have illness related to poor-quality water.

In addition, their water sources are more likely to be rapidly flowing rivers and streams. Even lakes differ from ponds, especially manmade ones. That doesn’t mean that ponds can’t be used as a water source for horses. You simply need to know what the risk can be and how ponds should be managed.

Potential Problems
Disease Transmission: A pond will be the watering site for more than just your horses. Wildlife will be attracted to them, too, and will leave behind droppings and urine to contaminate the water and vegetation around the pond. Many wild animals, both land-dwelling and aquatic such as muskrats or beaver, may be carrying Leptospira, a common contaminant in ponds. Leptospira infection can cause an acute febrile illness, abortion in pregnant mares or periodic ophthalmia (moonblindness). Other widespread organisms that may contaminate the water or surrounding grass are Listeria, Salmonella and E.coli. Opossums carrying Sarcocystis, the organism that causes EPM, may also be drawn to your pond, as will deer whose ticks may be harboring Lyme disease. The organism responsible for Potomac horse fever requires aquatic insects in its life cycle.

Agricultural Runoff: If there are livestock operations nearby, fecal matter and fertilizers in the surface runoff or shallow underground water sources can contribute to high-nitrate levels in the pond water and heavy algae growths. Industrial wastes recycled as soil treatments and even heavy manure contamination can also cause build up of toxic minerals in the pond.

Toxic Algae Blooms: Algae are an important part of the ecosystem within your pond. While they’re not necessarily pleasant to look at, fortunately most are harmless to the horse. However, rapid proliferation of some forms of algae can indeed be highly toxic, and livestock are lost to these poisonings every year.

Some blue-green algae, such as Microcystis and Anabaena, can cause extreme illness or death when an animal ingests contaminated water during a bloom, a period of rapid growth when the algae can produce a toxin. Not all blue-green algae growths are toxic, of course, but can turn so, causing experts to advise you to avoid letting animals have access to the water during blooms.

The two characteristics most often associated with blooms is the water turning a deep green so that it looks more like pea soup than normal greenish tinted pond water, and an "earthy" smell to the water. Symptoms range from skin rash and GI upset/diarrhea to rapid death.

Safety Issues: Unfortunately, farm ponds are a common site for drownings. Slippery footing and holes from muskrats or groundhogs make the area around the pond treacherous for horses. Horses, people and other animals may also venture out on frozen ponds and fall through.

The Water Looks Yucky

If you’re picturing a crystal clear pond with sparkling blue water where you can see all the way to the bottom, forget it. Just like bird baths or water troughs, outside collections of water quickly become an ecosystem complete with plants/algae. The normal color of pond water with a balanced ecosystem is greenish because of the phytoplankton, microscopic algae suspended in the water to depths that can be penetrated by sunlight. How far down into the water you can see will vary, but it should be at least 18 inches.

Ponds As Water Sources
The worst-case scenario for a pond as a water source is probably the picture many people have in their head – a pond nestled in the middle of a field, at ground level, that the horse’s can just mosey on up to, even wade in, anywhere they see fit. The problems with this picture are:

• Erosion of the banks from horse and other wildlife traffic.
• Dirt and manure being tracked into the pond.
• Runoff of water into the pond, contamination with manure, urine, dirt, pesticides or herbicides.
• Wildlife attracted to the pond.

The consequences of this are rapid filling in of the pond with dirt, high nutrient levels in
the pond contributing to heavy algae growth and risk of high nitrate levels, chemical contamination, turbidity from suspended soil, exposure to harmful micro-organisms.

The experts agree that ponds as water sources should be constructed on high ground where they aren’t subject to contamination from runoff, should be lined with specially treated concrete or other materials that will not interact with the water and are completely fenced off.

The water from the pond is used to fill stock tanks located downhill from the pond. Water flows by gravity through a drainage pipe. If the pond is at ground level, problems with bank erosion can at least be reduced by fencing off all but a small area of the pond, putting down stone at that access point and putting up fence or wiring in the water at a point that allows the horse’s to drink but does not give them enough room to actually walk out into the water. However, with a ground level pond you’ll still have the issues of organic and inorganic contamination from runoff.

Algae Management: Our sidebar lists some low-to-know maintenance methods for controlling algae in ponds, but under most conditions you will need to use a combination of these and direct intervention. The greenish color of ponds is caused by single-celled algae. They oxygenate the water and are a food for some fish.

It isn’t necessary, or even beneficial for the pond ecosystem, to completely eliminate algae. However, there are times when you need to control the growth. Algae treatments labeled as safe for use in livestock water include copper compounds and sodium carbonate peroxyhydrate. Copper is directly toxic to algae, while the peroxyhydrate-based products work like peroxide. Both are safe for plants, fish, birds, wildlife and your horses, and may be used in drinking water reservoirs, but overdosing with the copper compounds may kill some fish or plants.

Application rates are calculated in "acre feet," the pond’s top surface area in feet converted to acres (an acre = 43,560 square feet) x the depth in feet.

For example: My pond is 5 feet deep, 200 feet long and 80 feet wide. Algicide product calls for 1 gallon per acre foot. How much do I use? Surface area is 200 x 80 = 16,000 square feet. That is 0.37 acre x 8 feet = 2.9 acre feet. I need 2.9 gallons of product..

Peroxyhydrate based products break down to completely harmless substances like sodium carbonate, oxygen, bicarbonates. Algicides should be used before the algae burden reaches a critical level because nutrients from the decomposing algae they kill remain in the water and can contribute to another overgrowth cycle.

A third option is bacterial algae control using nitrogen-utilizing bacteria. All ponds naturally contain these bacteria but their activity tends to lag behind the algae in the spring, resulting in the algae populations getting a head start. By adding live bacterial cultures that compete effectively with the algae for nutrients, algae die off. These bacteria are not harmful to animals. See our chart for further details.

Another option for helping to control algae is to keep the pond water moving and well aerated. This breaks up clumps of algae and the better oxygenation gives bacteria an advantage over algae. Several companies offer compressor-driven pond aerator systems which range in price from a few hundred to a few thousand dollars. One obvious drawback here is they require electricity. Check your local Yellow Pages for contractors near you.

Another advantage of aerators is the prevention of ice formation. If you need this effect, be sure to check with the unit manufacturer for suitability in preventing icing. More exotic options include fountains and aerating systems that are wind-driven so don’t require electricity. Start up costs for these are $1,000 plus.

Bottom Line
There’s more to watering your horse from a pond than you might have thought. A clean, safe water source is essential for your horse’s heath. A pond can provide this, but only with careful planning, construction and ongoing maintenance. Be prepared to spend some money to get, and keep, safe pond water.