Winter temperatures in Germany have increased noticeably since the 1980s. The frequency of cold winters is decreasing, while mild winters and higher average temperatures are becoming the new normal. For this reason – and to save effort and expense – more and more boat owners are choosing to leave their boats in the water over the winter. However, there are a few things to bear in mind to avoid any nasty surprises.
The development of winter temperatures in Germany over the last 100 years shows a significant warming, especially in recent decades. This is a result of global warming, which is also having a noticeable impact in Central Europe. Since the 1980s, average winter temperatures have risen noticeably, and milder winters have become more frequent, especially since the 1990s.
While average winter temperatures in Germany in the 1950s were still around 0 °C to -1 °C, they rose to an average of +2 °C to +3 °C in the period from 2010 to 2020. Cold winters like the one in 1962/63 (average: -5 °C) have become rarer; currently, winters (especially those of 2019/20 and 2022/23) are even among the mildest since weather records began, with average temperatures above +3 °C.
Various climate models predict a further increase in winter temperatures of 1 to 3 °C by the end of the 21st century, depending on global emissions. Although occasional cold extremes could continue to occur due to changing air currents, the trend seems clear: mild winters will dominate in the years to come.
Winters continue to get milder – winter storage of boats in the water is becoming an interesting
prospect for many owners.
So why take your boat out of the water every winter and slip it on land, many boat owners ask themselves. The advantages of wintering in the water are obvious: on the one hand, you save a lot of costs, because a crane is no longer required, and you can also save on expensive storage space on land.
Another advantage could be that boats are protected from drying out, because certain hull materials, especially wood, can be damaged by excessive drying out in the (partially heated) hall.
Furthermore, you can start the season faster with the boat; there are no waiting times for boats that are already in the water to be launched in spring. With sailing boats, you can leave the mast in place. Finally – and this is also a good argument for wintering in the water: if the winter is mild, boat trips can also take place during the cold months.
When wintering boats on the water, the pros and cons must be carefully weighed up in advance.
However, the advantages are also offset by some significant disadvantages that should be considered.
On the one hand, there is the risk of freezing: especially in cold regions, there is a risk that parts of the boat will freeze and be damaged as a result. If the boat is also in the water in winter, there is a higher maintenance requirement, regular checks and various protective measures are required.
And last but not least: there is no guarantee that the winter season will remain ice-free. In particular, the risk of ice formation and movement of the ice should always be considered when considering leaving your boat in the water over the winter.
In windy conditions, ice floes can cause damage to the hull and moorings during the winter. Finally, access to the boat can also be restricted in winter: marinas can be difficult to access during the cold season, making it more difficult to check on your boat.
If you choose to leave your boat in the water over the winter, there are a number of proven systems to protect it from freezing in the ice.
If you still decide to leave your boat in the water over the winter, there are a number of options available to you. In addition to keeping the water free of ice using electrical systems (devices that keep the water moving prevent ice from forming around the boat; electric heating rods that are placed in the water can prevent the immediate surroundings from freezing), air bubble systems and submersible pumps have proven particularly effective in practice.
In so-called bubbler systems, air bubbles are pumped under the water, creating a water circulation that can prevent ice from forming around the boat during winter storage in the water. These air-bubble systems can be installed for individual berths or for entire marinas or certain jetties. These systems are particularly effective in sheltered harbors or quiet coves.
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The way they work is relatively simple: a compressor supplies a (usually plastic) pipe system installed below the surface of the water with compressed air. The pipes, which are suspended in the water about half a meter below the boat, have holes about 1-2 mm in size at intervals of about one meter, through which air can escape and rise in the form of bubbles.
These air bubbles ensure that the water surface is constantly in motion, preventing ice from forming. Depending on the temperature, the compressor does not have to run constantly, so it is advisable to connect it to a timer to set specific intervals.
In addition to the so-called bubbler (air bubble) system, many owners opt for submersible
pumps
Those who prefer a simpler solution opt for the use of one or, better still, two submersible pumps. They pump (warmer) water from below the boat’s hull and keep it free of ice by raising the temperature at the surface (and also by moving the water). This is possible due to the so-called density anomaly of water: below a temperature of about 4 °C, surface water does not sink.
Instead of the associated cooling of deeper water layers and a complete freezing from below, different thermal layers can form. In two to three meters of water depth, temperatures between 2-4°C can therefore prevail in winter, while ice has formed on the surface.
To avoid the pumps having to run around the clock, a combination with a timer is also recommended here (ideally connected in series with a temperature switch that is activated by a floating temperature sensor). Note: the pumps should also be able to handle dirty water, they should be positioned deep enough and correctly under the boat and secured against movement.
In addition to these two technical systems, you can of course also try to free your boat from ice manually. However, this requires regular checks and constant breaking of the ice. This labor-intensive method will only make sense, if at all, in appropriate weather conditions and with thin ice in small marinas.
The be-all and end-all of winterizing your boat is good preparation
In any case, a planned winter storage of the boat in the water should be well prepared. In addition to the procurement / production of the electrical / electronic systems described above, it is necessary to ensure that the hull and underwater area is in order: a fresh painting prevents the growth of algae and mussels. Any cracks or weak points in the hull must be repaired beforehand to avoid leaks, and all passages and seals should be checked in advance.
In any case, the aspect of safety and control should not be underestimated when wintering in the water. A protected harbor is essential for this project, as open waters can be dangerous, and you should make sure that the boat is far enough away from the dock.
Furthermore, when wintering in the water, you should plan for robust mooring lines and enough fenders to avoid damage caused by ice movements. A tight tarpaulin (freshly impregnated if necessary) should be used. And finally, regular inspection of the boat is important in winter to detect damage early.
If you lack the technical knowledge or time, specialist companies can also help with winter storage in the water. In general, every owner should carefully consider whether wintering on land is not a safer and more stress-free option in the long term, depending on the region and weather conditions. The type, composition and length of the hull also play a role here.
