In brief
A pond that holds back winter runoff and lets it seep slowly into the ground; it also serves as habitat and as a cooling surface in the landscape.
What is a retention pond?
A retention pond holds back water that would otherwise run off. In regenerative land use the term refers to a pond that catches surface runoff, above all from the autumn and winter rains, and releases it slowly into the ground. The water does not disappear: it seeps through the bottom and the banks into the soil and, depending on the geology, down to the groundwater. Springs and wells further down can benefit. At the same time the pond is a habitat for amphibians, dragonflies and birds, a drinking place for wildlife and a cooling surface in an otherwise dry landscape.
The term is used in two senses. In urban drainage engineering, retention ponds are basins that catch the peak runoff of heavy rain from sealed surfaces and release it in a controlled way. In permaculture and in the water retention landscapes associated with Sepp Holzer, the focus is different: the pond is part of a landscape that is meant to keep rain in the area instead of letting it run off. This article uses the second sense.
The distinction from a storage pond lies in the bottom. A storage pond is meant to keep water for the dry season and is sealed as well as possible. A retention pond may leak, because that is its purpose. Many real ponds serve both purposes in part.
What matters on a dry slope
Location comes first. A pond belongs where runoff gathers naturally, in a hollow or below a sufficiently large catchment, and where its overflow can leave safely. Bill Mollison, in his Permaculture: A Designers' Manual, devotes much attention to placing dams and ponds in the landscape so that water can be distributed by gravity. Every pond needs a secure spillway: if a full pond overflows in an uncontrolled way, the water erodes the dam, and a breached dam can cause damage downstream.
The bottom determines how the pond behaves. Clay soils seal by themselves, sandy or rocky ground lets water through. Sepp Holzer describes sealing pond bottoms without plastic by compacting moist soil with the excavator bucket. Whether that works depends on the soil, and it is not a question one can answer from a distance.
Evaporation is the great objection in dry climates. In a hot, windy summer, an open water surface loses a great deal of water. Deep ponds with a small surface lose relatively less than wide, shallow ones, and trees and windbreaks on the sunny and windward sides reduce the loss further. A retention pond whose water has already seeped into the soil before summer avoids part of the problem, since water in the soil evaporates far more slowly than water in the open. In a Mediterranean summer such a pond may fall dry, and that does not mean it has failed.
For planting, native wetland and aquatic species of the region come first. Several popular pond plants are excluded: water hyacinth, water lettuce, parrot's feather and water primrose are on the EU list of invasive alien species of Union concern. For Terra Humana, a plant on the Union list is never used.
How Terra Humana understands it
For Terra Humana the retention pond is not the first step but one of the last. Before water is collected in a pond, the land itself should be able to hold it: through plant cover, through humus, through swales and contour work as in keyline design. A pond on a slope whose soil sheds every rain fills with mud and dries out quickly.
Where a pond makes sense, it brings real gifts: moisture in the soil below, a place for amphibians and birds, a reserve in case of fire. These gifts are weighed honestly against evaporation, the safety of the dam and the effort of building it, without the pond becoming an end in itself.
Frequently asked
What is a retention pond?
In regenerative land use, a retention pond is a pond that catches surface runoff, mostly from the winter rains, holds it back and lets it seep into the ground over weeks and months. Unlike a sealed storage pond, it is not mainly meant to keep water for irrigation but to recharge soil and groundwater. At the same time it offers habitat for amphibians, insects and birds and cools its surroundings. In urban drainage engineering, the same term refers to stormwater basins that hold back peak runoff.
What is the difference between a retention pond and a storage pond?
The difference lies in the purpose and in the bottom. A storage pond is sealed as well as possible, with clay, compacted soil or a liner, so that water remains available for the dry season. A retention pond may lose water downwards, because that is exactly its job: the water that leaves the pond through the bottom feeds the soil and the groundwater below. Many ponds lie in between. In a Mediterranean summer a retention pond can fall dry, which does not mean it has failed.
Where should a retention pond be placed?
Where runoff gathers naturally: in a hollow or below a sufficiently large catchment, and where its overflow can leave safely. Every pond needs a secure spillway, because a full pond that overflows in an uncontrolled way erodes its own dam, and a breached dam can cause damage downstream. The bottom matters too: clay soils seal by themselves, while sandy or rocky ground lets water through. Bill Mollison devotes much attention to placing dams and ponds in the landscape so that water can later be distributed by gravity.
Do ponds lose a lot of water to evaporation in the Mediterranean?
Yes, open water evaporates strongly in a hot, dry, windy summer, and this is the most serious objection to ponds in dry regions. How much is lost depends on the surface, depth, shade and wind exposure. Deep ponds with a small surface lose relatively less than wide, shallow ones; trees on the south and west sides and windbreaks reduce the loss. A retention pond whose water has seeped into the soil before summer avoids part of the problem, because water in the soil evaporates far more slowly than water in the open.
Which plants belong in a pond?
Native wetland and aquatic plants of the region, which also provide habitat for local animals. Several popular pond plants, on the other hand, are excluded: water hyacinth, water lettuce, parrot's feather and water primrose are on the EU list of invasive alien species of Union concern. For Terra Humana a simple rule applies: a plant on the Union list is never used. Moving plants from one water body to another also deserves caution.
Related terms
See this in practice
Sources
- Mollison, B., Permaculture: A Designers' Manual, Tagari Publications (1988)
- Holzer, S., Sepp Holzers Permakultur, Leopold Stocker Verlag (2004)
- European Environment Agency, Climate-ADAPT case study: Tamera water retention landscape to restore the water cycle and reduce vulnerability to droughts
- Regulation (EU) No 1143/2014 on invasive alien species and the Union list adopted under it
Last updated: 2026-10-12