POND CARE
Confessions of a Steward
Words by Joel Salatin
Let’s talk ponds. Few things adorn a farmscape more beautifully than well-placed functional ponds. But like all living things, ponds go through a cycle. When they’re freshly built, manicured excavation makes them look sharp. Over time though, their shoulders sag, silt builds up, vegetation clogs, and muskrats dig holes in the dam. These are all common maintenance issues that develop as a pond matures. Having built close to 30 ponds on our farm and rental places over the years, I’ve enjoyed all phases of the early to late process. In this column, I’ll do my best to share advice garnered from these years of experience.
When building a pond, the steeper the sides the better. And the deeper the better. Shallows encourage lots of vegetation. You always want some vegetation, but wide shallow shelves don’t offer the benefits of deeper waters. Depth ameliorates temperature by offering cool water in the summer and warmer water in the winter.
If the pond freezes all the way to the mud, fish and turtles lose habitat. Sides can never be vertical because they’ll slough off over time. But they can be steep rather than gradual, and that makes for a more functional pond. Even with steep sides, enough cattails and other hydrologic vegetation will grow around the edges to filter and cleanse the water.
Deeper water provides more habitat variety. Some critters like shallow, almost marshy conditions while others prefer deeper water. On a hot summer day, a shallow pond can get warm enough to kill fish. Warm water holds much less oxygen than cold water. Fish move to oxygen-rich areas depending on water temperature.
Stagnant water is a common problem if the pond doesn’t have constant flow from a spring or small creek. I’ve only built a couple of ponds that have year-round trickle inflow; the rest fill during run-off events and then sit still the remainder of the season—usually during the summer. The deeper the pond, the less likely it is to become stagnant because shallow ponds grow far more vegetation and therefore over-supply rotting biomass on the water’s surface.
Shallow ponds that tend toward stagnation benefit from floating windmill aerators to stir the water and keep it more oxygenated. The other primary cause of poor water quality is nutrient-rich run-off, especially manure. Never spread compost or manure during the dormant season. Place mineral boxes or any feed supplements on ridges and never in valleys. This allows surface runoff time to drop nutrients on its way to the valley.
A pond should have two pipes in the dam. One in the bottom to drain it, the other in the top as an outflow. On the non-excavated dam edge, a catastrophic overflow offers dam protection in case of flooding. The broad, flat overflow should be gentle and grassed so that if water does go through it, it spreads out thin and doesn’t cut an erosion ditch. If the outflow pipe fills or clogs, and the lowest spot is the top of the dam, you’ll lose the dam in a few minutes. I’ve been there and done that. A dam breach means a lost pond.
The outflow pipe needs to be big enough to handle significant rain or snow melt events, but not necessarily a flood event. I much prefer several 6-inch sewer pipes through the top of the dam rather than a single large culvert. The smaller pipes allow the water level to be higher in the dam basin, and they don’t require as much dirt on top to protect them from collapse if you drive over the dam.
In our area, the most common pond construction mistake is not putting in enough outflow pipe capacity. Most people don’t put in any outflow pipe at all. They reason that, since water doesn’t flow in all the time, the outflow depression will simply grass over and handle the occasional outflow. But it never does. All it takes is one wet spring or one significant snow melt to make outflow run for a month; that’s enough time to suffocate the grass and cut an erosion notch in the side of the dam. Within a couple of years, the ditch deepens, the pond level drops by a couple of feet, and what was once a functional, pretty pond becomes a stagnant mudhole. I can’t count how many of these I’ve seen.
Do it right. Install enough outflow pipe to protect the fragile dam and sod around the downhill side of the pond. That’s the most important thing you can do to ensure a long-lasting, low-maintenance functional pond.
The bottom drainpipe can be a 2-inch PVC pipe with a valve on the downhill side. It should have two or three pond collars to keep seepage from creeping down the slick wall of the PVC pipe. These can be commercially purchased or poor-boy-installed (my preference) with a bag of mortar mix. These concrete plugs, or collars, adhere to the PVC and force any seepage to the outside and into the dam.
In general, if you see salamanders, frogs, and turtles, your pond water quality is good. If you don’t see significant critters swimming around, you may have poor water quality. Steep sides and clean in-flow are the two key components of non-stagnant, good-quality water. Depth should be at least 8 feet. Deeper is better if you can.
All of this means the worst thing you can do to a pond is give cows access to it. If cows drink from a pond, they gradually push the edges in. As they push the edges in, they walk out farther to get the better water that’s farther away from the muck on the pond bottom. When they walk out farther, they leave the shore and poop and pee into the water. This damages the pond’s water quality, which is bad for both the pond ecology and the cattle. Never give livestock access to a pond. Fence it out and pump water, drain, or siphon water to the animals. Nothing destroys a pond faster than livestock access.
Contrary to what many believe, one of the best things you can do for your pond is to fluctuate the water level. That means ponds should be viewed like a bank account. Sometimes they’re up and sometimes they’re down. They’re meant to be used. P.A. Yeomans, the Australian who developed the keyline system and wrote the classic book Water for Every Farm, said that every farmer should aspire to two things: eliminate surface runoff by catching that water in ponds, and never end a drought with a full pond.
In other words, ponds are not just for pretty. They are valuable resources to be strategically leveraged during droughts. Fluctuating the water level exercises the pond ecology and is the number one way to protect the dam from burrowing rodents like muskrats. All muskrats dig their holes at water level. They want to swim to the mouth of their tunnel. They’re quite uncomfortable having to climb out of the water and hike to the front of their house.
As a result, the number one deterrent to dam damage is to periodically (at least once every other year) drop the pond level several feet. Any amphibious critter that wants to burrow at water’s edge will leave when the pond drops. Fluctuation also changes the vegetation around the edges and lets you make a visual assessment of dam integrity. If water stays at the same level, you can never do a good inspection to know if deterioration is occurring.
Droughts happen routinely. Irrigating from your pond not only helps grow pasture and other crops but also is a great way to change the level of the pond. Every couple of years, during an extended drought, we literally pump our ponds dry. When that happens, take advantage of the situation and clean it out. Since water grows far more life per cubic foot than a terrestrial environment, plants and animals live and die in the pond, building up an anaerobic fertility-rich muck. Occasionally cleaning that out benefits the pond and gives your land some valuable nutrients.
I’m convinced that if a farm had enough ponds, it could virtually maintain its fertility program simply by draining one per year and spreading the muck on the fields. The reason life grows prolifically in a pond is because it doesn’t have to spend 30 percent of its energy defying gravity. Moving 100 pounds through water is much easier than moving 100 pounds across the land. Bill Mollison’s Permaculture: A Designer’s Manual notes that some 10-20 percent of a plant’s energy is expended defying gravity, including standing into the wind.
Ponds, then, can be a significant fertility engine by offering a muck application rotation. If you had 20 pounds and cleaned out one per year, it would go a long way toward terrestrial fertility. Draining gives an opportunity, too, to cut any saplings growing on the dam. On our farm, we like to run an electric fence just outside the water on the inside of the dam so the cows can graze the back side of the dam and keep it clean. You don’t want trees growing on the dam because the roots will make water channels and eventually undermine the impermeable properties of the clay.
Some kinds of vegetation are beneficial, like duckweed. If you have an explosion of duckweed, be thankful. That indicates excellent water quality, and the plant sucks up extra nutrients to cleanse the water. Algae problems usually come from low oxygen, stagnation, shallow water, and excess nutrient runoff loads. In such cases, change what’s happening on the land leading into the pond, deepen the pond, or steepen the sides. That’s the homework.
One more thought: better to have many small ponds than one huge one. Too many folks never build a pond because it’s too expensive to build the grandiose one they have in mind. Miniaturize the project. One small pond is much better than none at all. You can put three ponds in a valley, over time, like an aquatic ladder.
Few land improvements are as functional and beautiful as well-made functional ponds. When the beavers were in charge, 8 percent of America’s landscape was water. Even though we’ve built 20 ponds on our farm, we’re still under 1 percent. We have a long way to go to catch up with the beavers.