What is a Water Retention Landscape?

In brief

A landscape shaped so that rain stays in the area: ponds, swales, terraces, plant cover and soil care hold it back; an approach shaped by Sepp Holzer.

A water retention landscape is not a single structure but a way of shaping a whole area so that the rain falling on it stays there. Instead of draining water away as quickly as possible, as much of modern land use does, it is slowed down, spread and allowed to sink in. The tools are familiar: ponds and lakes without artificial sealing, swales and ditches along the contour lines, terraces, permanent plant cover, trees and careful soil management. What is new is the combination. The individual elements are linked into a system in which water passes from one to the next and finally into the soil and groundwater.

The idea behind it is the small water cycle. When rain soaks into a landscape instead of running off, it feeds soil, plants and springs, evaporates locally, cools the air and can come back down as dew or rain. Where the land is bare and sealed, this cycle breaks down. Proponents see water retention landscapes as a way of repairing it from below, plot by plot.

Sepp Holzer and Tamera

The approach is closely linked to Sepp Holzer. On the Krameterhof, his family's mountain farm in the Lungau region of Salzburg, which lies at roughly 1,100 to 1,500 metres on the slopes of the Schwarzenberg, he created terraces, ponds and mixed plantings over decades, in a climate that is anything but favourable for farming. His books, among them Sepp Holzers Permakultur of 2004, and his work as an adviser have carried the approach to many countries. Holzer himself is a disputed figure: admired as a practitioner, and known as the "agricultural rebel" who repeatedly came into conflict with the authorities over his methods.

The most documented example in southern Europe is Tamera, a community in the Alentejo in southern Portugal, a region with about 600 millimetres of rain a year and recurring droughts. According to the case study on the European Environment Agency's Climate-ADAPT platform, the water retention landscape there was designed and built between 2006 and 2015. On 154 hectares, 29 lakes and retention spaces were created, and the area of water bodies grew from 0.62 to about 8.3 hectares. The project reports a new spring that appeared within the first year, its own drinking water from wells fed by the landscape since 2011, and a doubling of transitional woodland. The case study puts the investment for such a landscape in the order of half a million euros. The case study is frank about its limits: a cost-benefit calculation for 2015 to 2050 came out negative, and several benefits could not be quantified. Its figures rest largely on Tamera's own material. The first lake, built in 2007, went back to a proposal by Sepp Holzer, as Tamera reports.

Critical voices

The approach has enthusiastic supporters and well-founded critics, and both deserve a hearing. The most frequent objection concerns evaporation: in a hot, windy summer, open water loses a great deal, and in dry regions every square metre of water surface has to justify itself. A second concerns the evidence: independent, long-term hydrological measurements that separate the effect of the retention landscape from rainfall fluctuations are rare. A third concerns neighbours: water held back upstream can be missing downstream.

A contribution in the Berliner Zeitung from October 2023, written in a sympathetic tone, made the limits visible at Tamera itself: the first lake was only half full and had been shrinking for about five years as rainfall declined. At the same time, intensive agriculture in the region, with eucalyptus monocultures and berry crops that draw groundwater from great depths, is lowering the water table, something a single project cannot offset. A water retention landscape can improve the water balance of its own area; it cannot replace a region's water policy.

How Terra Humana understands it

Terra Humana shares the core of the idea: water belongs in the land, not in the gully. On a dry Mediterranean slope, holding the winter rain is the first condition for everything else, and in this sense every swale, every terrace and every patch of ground cover is part of a water retention landscape.

Where we are more cautious is the large open water surface. Five dry months, steep slopes and the safety of dams speak for beginning with the soil: plant cover, humus, rainwater harvesting along the contour, and only then, where location and water balance allow, a pond. We do not see the water retention landscape as a template to copy, but as a direction: one that has to prove itself on each site with honest observation.

Sa Medada

What this looks like at Sa Medada

The LiDAR wetness map of Sa Medada shows a comparatively dry main area with moister channels along the edges. Holding water is one of the three beginnings of Project Eden, together with pioneer plants and ground cover. Swales are planned, none has been built yet. The first step is to keep the winter rain in the soil of the slope, before any thought is given to open water.