Ponds

Construction (materials, technical sheet / cross-sections)

No pond without sufficient and clean water. A pond is mainly fed by groundwater and (run-off) rainwater. If you have a wet or lower area on your property, this may be a good place to build a pond.

You can consult soil maps online to find out your soil type(www.geopunt.be – nature and environment – soil – Soil map: soil types), but to have a good idea of the local groundwater level, it is best to use a soil corer to look for soil rust or groundwater. The zone with rust color shows a fluctuating groundwater level. You then drill further in search of the gray (reduction) zone indicating permanent groundwater level. You ideally find this boundary at a maximum depth of 1.50m. You can then dig a pool 2m deep that will hold water during an average summer.

You can also monitor the well for several months to see the fluctuations of the groundwater level throughout the year, focusing on August/September, when the groundwater level is usually at its latest.

Gray reduction zone – permanent groundwater level Rust color – fluctuating groundwater level

Is presence of groundwater checked off, then you can see if the area around the pool is suitable. Amphibians use pools to reproduce, but “live” most of the year on land. Therefore, the environment of a pond must also meet some requirements:

• Small landscape elements (KLEs) in a radius of 200-500m, such as nearby pools from which species can migrate to the pool and hedges, wood edges, shrubs, orchards, groves where amphibians can find protection and food. You can also plant these yourself if the area is not yet suitable.
• Not too close to tall KLEs. Best keep a minimum 15m distance from trees on the west side of the pool (less leaf fall) and 25m on the south side (sufficient light).
• To maintain good water quality , your site is best located away from fertilized fields or has woody vegetation between them as a buffer. Streams can also carry polluted water to your pool. So it is best not to connect to surrounding streams or canals and keep a distance of 20 to 30m in case they flood.

Landscape integration

Construction

You can determine the shape and size of your pool based on the available space and your needs:

• We recommend a water area of at least 100m2. If you have the space, it is better to choose a size of 150m2 to 200m2. Larger pools are more varied and less vulnerable to drying out and siltation.
• The shape is best whimsical or eg in the form of a kidney, so you create more variety and riparian zone.
• The slopes of your pool should be gentle/faint (20° to 25°) so that a shallow riparian zone is created. This is especially important on the northern and western sides, as that is where the incidence of sunlight is brightest so the water warms up quickly in the spring as a spawning ground. Small mammals and amphibians can then also get out of the water more easily. The southern and eastern slopes may be steeper (30° to 40°), but they should not be. Therefore, because the slopes should not be too steep, you cannot make small pools as deep as large ones.
• The ideal depth of a pond is between 1.5m and 2m deep, 50cm below the measured lowest groundwater level to prevent drying out in summer and freezing in winter the.
• The bottom surface should also have an area of at least 2m2.
• NO sealing/foil is needed in the excavated ‘pit’, groundwater will quickly fill the pool and in extreme drought, a pool may run dry once in a while (preferably not until late August in function of reproduction and not annually).
• It’s best to let a pool evolve spontaneously. So don’t put out fish, amphibians and aquatic plants, these will come naturally.
• In a cattle drinking pool, fencing off part of the pool benefits the (water) quality of the pool. This is because it prevents cattle from trampling all the banks and their droppings from entering the pool. It is best to fence the most valuable north and west banks so that biodiversity has a place here.

The excavated soil is best processed on your plot, which is the most cost-effective. You can spread it out locally, use it as backfill or incorporate it into a mound. Usually, spreading has the best long-term landscape results. However, in flood-prone areas, you may be required to drain the soil and that comes with a higher price tag.

In pond restoration, it’s best to lay the excavated silt to dry for several days at the water’s edge. This allows animals scooped up with it to get back into the water and reduces the excavated volume.

Time

The best time to dig a pool is late August to late September, groundwater is usually low then. If you rebuild a pool, it is best to dig from late September to late October, by which time most animals are no longer in their reproductive period, but not yet hibernating in the pool.

Maintenance

• Remove storage and overhanging branches of trees and shrubs in and near the pond
• Mow the edges of the pool, leaving ^1/4th each time, and dispose of the clippings
• Remove invasive aquatic plants so that 50% of the area remains uncultivated
• Remove algae as best you can
• Remove fallen leaves or dead plants
• Remove silt every 5 years with a dredge bracket, crane or tractor. Ideally, spread the work over 2 years and clear half a pool per year (minimize disturbance).
• Place grass clippings, aquatic plants, leaves and silt on the bank for 1 day so animals get back to the pool