Does Well Water Harm Pond Environments?

Small pond owners get creative during scorching summer months to save treasured waters and fish. Many successfully solve the challenge supplementing water levels with wells.

If you’re considering such measures, conduct a standard water test before pumping. You should know salinity levels and related chemistry. Many folks are not aware well water doesn’t contain oxygen. It should be aerated by running across rocks or similar objects before reaching the pond. Thoroughly analyze the well’s capacity. Don’t pump for extended periods and risk depleting the reservoir.

Dr. Billy Higginbotham, Extension fisheries and wildlife specialist, advises we can kill fish with well water that’s perfectly good to drink. As water levels drop, pond surface area shrinks. When surface areas shrink, the pond’s ability to absorb oxygen is reduced. Even during a normal summer, the most likely cause of fish loss is oxygen depletion. Hot, windless days often reduce a pond’s ability to absorb and hold oxygen. Cloudy days compound the problem by slowing photosynthesis among aquatic plants, a process that produces oxygen. Even though well water is clear and clean, certain due diligence should be completed before adding to the pond.

Two important issues are — quality and quantity. The most critical is a difference in quality between pond and well water. Too large a change in temperature or pH can harm fish. With pH, a change of more than one unit, up or down within a short period of time, can be negative. Abrupt temperature changes of 10 degrees or more, up or down, can put fish at risk. The second consideration is quantity. Dr. Higginbotham explained, if a garden hose is running into a pond, change in water quality will be small over a long period of time, particularly in a larger pond.   Fish have time to adapt. But with a 6-inch line pumping fire hose quantities, the change in quality happens much more quickly. It’s not just change; it’s the rate of change. Even if pH is similar, a sudden wholesale temperature change can also result in fish loss. Such changes can happen naturally during summer if an extended period of high temperatures is followed by a heavy rain. During this season, ponds become stratified. The top stratum is warmer because warm water, like warm air, rises. Lower or bottom stratum remains cooler. Moreover, dead organic matter builds up at lowest levels. Since bottom organic matter is deprived of oxygen, it does not decay.

A cool rain or strong wind from a summer thunderstorm can cause the pond to turnover as the sudden cooled top layer sinks and mixes with the lower layer. This pushes dead organic matter to the surface. When dead organic matter is exposed to oxygenated water, natural decay proceeds at a vigorous rate. These increased rates reduce oxygen levels and result in fish kills. Pumping large amounts of cool water into the surface of a stratified pond can replicate a pond turnover. Even if pond pH and temperature are similar to well water, it’s still possible to deplete oxygen if the landowner isn’t careful. According to Dr. Higginbotham, this occurs because well water has no appreciable absorbed oxygen. It may have high levels of carbon dioxide.

To remedy this possibility, Dr. Higginbotham recommends breaking up well water before it enters the pond. This process of agitation and increased exposure to air can be done by various methods. The simplest is just let pond water run over balled-up hardware cloth, rocks, or similar surfaces on its way to the pond. Other methods involve dropping water from a series of boxes or rock piles arranged in a stair-step or waterfall. Anything that induces aeration before water enters the pond. He suggests a small flow of water is easier to break up than a large one.

Small ponds may experience filamentous algae as water temperatures decline to Spring-like levels. If you notice such conditions, call to discuss using tilapia or copper-based algaecides to manage growth. Watch for increased fish presence where water enters the pond. Cooler temperatures and elevated oxygen levels attract them.