After winter, a garden pond returns to activity gradually, but the changes taking place during this period are dynamic and often difficult to interpret clearly. One of the most common warning signs is a drop in water level.
In practice, this may result from natural physical processes as well as from a structural leak. That is why the key is not to react too quickly, but to make an accurate diagnosis. A pond is a closed system in which the water level is directly connected to its biological, chemical, and mechanical balance. Any disturbance, even a small one, can trigger a chain of changes that may eventually become visible as cloudy water, poorer fish condition, or unstable water parameters.

Natural evaporation — how much water can disappear without a problem? #

Evaporation is a completely natural process and, in many cases, is responsible for most water loss observed in spring and summer. Its intensity depends on several factors that work together, including air temperature, sunlight, humidity, and air movement above the water surface.

In practice, this means that:

• on cooler, windless days, water loss may be minimal
• on warm and windy days, the water level may drop by as much as 3–5 cm per week
• shallow ponds lose water faster than deeper ones because they have a larger evaporation surface in relation to their volume.

Additionally, after winter, filtration and water circulation are often restarted, which increases the contact between water and air and speeds up evaporation. As a result, the drop in water level may seem sudden, even though it is caused only by natural physical processes.

When does a drop in water level stop being normal? #

The signs that should raise concern are quite characteristic, although they are not always obvious at first. In practice, a leak most often appears as a repeated or accelerated drop in water level.

It is worth taking a closer look when:

• the water level drops despite stable weather conditions
• the water loss is greater than a few centimeters within 2–3 days
• the water stops dropping at a specific level
• permanently wet areas appear around the pond

This last sign can be the most misleading, as moisture near the edge may result from both a leak and capillary action — a process in which absorbent materials such as soil, underlay, or plant roots draw water out of the pond.

A test that clears up any doubts #

The simplest and most reliable way to distinguish evaporation from a leak is a comparison test. Fill a container with pond water and place it in conditions as similar as possible to those in the pond. If, after 24–48 hours, the water level in the pond drops more than in the container, the loss is not caused by evaporation alone. This method eliminates the influence of temperature, wind, and sunlight, allowing you to focus only on the difference that may indicate a possible leak.

The most common causes of leaks after winter #

In winter, a pond is exposed to conditions that can noticeably affect its structure. Freezing water expands, creating stress in the material, while repeated freezing and thawing can further weaken its durability.

The most common sources of problems are:

• microcracks in the pond liner caused by ice movement
• leaks in joints and folded areas
• mechanical damage caused by plant roots or stones
• leaks in installations, such as pumps, filters, or overflow systems.
• an improperly shaped pond edge that allows water to escape outside the pond.

In practice, the most problematic areas are often those that are not visible at first glance, such as sections of liner hidden under stones or vegetation.

How to find the leak without dismantling the pond? #

The most effective method is based on observing the natural drop in water level. If you allow the water to fall without topping it up, the process will eventually stop. This level indicates the height at which the leak is located.

Thanks to this:

• you narrow the search area down to a specific zone
• you can focus on carefully inspecting a specific section of the pond liner
• you do not have to take apart the entire pond unnecessarily.

It is also worth remembering that some leaks are very slow and require patient observation, especially in larger ponds.

The impact of leaks on pond biology #

Water loss is not only a technical problem. It is also a factor that directly affects the functioning of the entire ecosystem.

This can change:

• the concentration of nitrogen compounds
• pH stability
• the effectiveness of biological filtration

The nitrogen cycle, which is responsible for converting toxic ammonia into less harmful forms, works properly only when conditions in the pond remain stable. Fluctuations in water level can disrupt this process, increasing the risk of poorer water quality and stress in fish. In addition, frequent topping up with fresh water changes the chemical composition of the pond, which may affect the microorganisms responsible for biological filtration.

What to do after detecting a leak? #

The action you take should depend on the scale of the problem.

In the case of minor damage:

• small leaks can often be fixed using repair patches or pond-safe sealing products
• the stability of the repaired area should be monitored.

For more serious problems:

• it may be necessary to replace a section of the pond liner
• sometimes the pond edge or installation setup needs to be corrected.

After removing the cause, it is worth focusing on restoring biological balance, as even a short-term disturbance can affect the bacteria and the entire filtration system.
For this purpose, Aquaforest Bio Starter can be used to support the recovery of the pond’s biological system.

If it is only evaporation — how to act consciously? #

Natural water loss also requires monitoring, because regular topping up affects the pond’s parameters.

A good practice is to:

• top up the water in small amounts
• avoid sudden temperature changes
• monitor pH and hardness (Aquaforest pH Minus)

It is also worth remembering that fresh water often contains minerals and elements that can affect the pond’s chemical balance and algae growth.

Summary #

A drop in water level after winter is a natural phenomenon, but it requires careful observation, as the line between evaporation and a leak can be very thin. Simple tests and regular monitoring help identify the problem and avoid its consequences. A well-functioning pond is not only about reacting to problems, but also about detecting them early. Pond tightness, stable parameters, and efficient filtration form a connected system — if one element stops working properly, the others will quickly be affected.