The frustration of a farm pond losing water is common for landowners, who rely on these reservoirs for irrigation, livestock, and fire protection. Diagnosing the issue requires a systematic approach, as water loss is rarely due to a single cause. Multiple factors—ranging from atmospheric conditions to underlying geology and structural integrity—contribute to a pond’s water budget, and a correct diagnosis is the first step toward an effective solution.
Atmospheric Water Loss: Evaporation Rates
Evaporation is the most consistent and unavoidable form of water loss from any pond surface. This process depends on local weather conditions; high air temperature, low relative humidity, and strong wind speed accelerate the rate at which liquid water converts to vapor. The total surface area of the pond is also a factor, as a larger exposed area means a greater volume of water is subject to this transformation.
In hot, dry, and windy conditions, farm ponds can lose water rapidly, with rates commonly ranging from one-quarter to three-quarters of an inch per day. Under typical summer conditions, a loss of about one-half inch per day is common. To determine if evaporation accounts for the observed drop, use a simple measurement technique, such as placing a fixed-level container like a pan in the pond to compare the water level drop in the pan (evaporation only) to the pond’s overall drop (evaporation plus seepage/leakage).
Geologic Water Loss: Seepage and Soil Type
Seepage occurs when water percolates through the pond’s floor or banks into the surrounding soil or groundwater. This is often the most challenging problem to identify and correct because it is dictated by the soil’s permeability. Soils with high clay content are desirable for pond construction because the small, tightly packed particles limit water movement, while sandy, gravelly, or loess soils are highly permeable and prone to excessive seepage.
A well-constructed pond on suitable soil should experience an acceptable seepage loss of two inches or less per month. However, some geologic formations can cause water loss, such as continuous layers of sand or gravel beneath the pond basin. Fractured bedrock, like that found in limestone or karst regions, can create fissures and sinkholes that act as direct conduits for water to escape into the underlying aquifer.
When investigating seepage, compare the water level drop against the estimated evaporation rate; if the total loss exceeds the calculated evaporation by a significant margin, seepage is the likely culprit. Signs of seepage can include perpetually wet or unusually lush vegetation on the downhill side of the pond, indicating where the water is exiting. Deep ponds are more susceptible to seepage because the increased water pressure at the bottom forces water more readily through porous areas.
Structural Water Loss: Dam and Spillway Issues
Structural water loss relates to failures in the engineered components of the pond, primarily the dam and the spillways. The integrity of the dam embankment is dependent on proper construction, specifically the compaction of clay-rich soil during the build to form a water-tight core. A lack of compaction or the use of improper materials can lead to leakage through the dam itself.
Burrowing animals, such as muskrats and beavers, dig tunnels through the dam embankment, creating direct pathways for water to escape. Decay of tree roots left in the dam structure can leave behind voids and channels that compromise the embankment’s integrity. Water can also leak around the principal spillway, which is the pipe used to maintain the normal water level.
If the anti-seep collars installed on the drainpipe were improperly bonded to the surrounding soil, water can track along the pipe’s exterior, leading to a leak. Inspecting the entry and exit points of the pipes and looking for soft, wet areas on the downstream face of the dam can help pinpoint these structural failures. Erosion can also lower the height of the dam or create channels that allow water to flow over the top, resulting in uncontrolled loss.
Management Water Loss: Usage and Inflow Balance
Beyond physical leaks and evaporation, a farm pond loses water when demand exceeds supply, which is a matter of balancing outflow and inflow. Management factors include intentional water removal, such as pumping for crop irrigation or other farm uses.
Irrigation systems, even for small acreage, can draw down a pond quickly, especially during peak summer months. Livestock also contribute to the water loss equation, and while individual consumption is small, a large herd can account for a substantial daily outflow. Additionally, if livestock are allowed direct access, their activity can damage the banks and increase erosion, indirectly contributing to structural issues.
Pond inflow is primarily determined by its water source, whether it is fed by surface runoff, a stream, or groundwater. During prolonged drought conditions, the inflow from a small watershed may be insufficient to offset the combined losses from evaporation and necessary usage. A comprehensive water budget assessment is necessary to determine if the pond’s storage capacity and its water sources are sufficient for the intended agricultural demands.