Water-wise Landscaping : Surface Water Catchment

Alarmingly, South Africa’s average annual rainfall is about half that of the world average. Yet we throw away this precious resource when we don’t harvest the little rainwater we do get or fail to make the most of its run-off in our gardens. Along with water-wise gardening techniques, rainwater can actually provide most of the water needed by our gardens, particularly when its run-off is redirected to beds.

Here, five simple ways to hang onto the valuable rainwater in your garden (and save significantly on your monthly water bill!):

1. Terracing Tactics

Flat or slightly depressed terraces are a good way to harvest rainwater, particularly on sloping sites, that might otherwise be lost to run-off. Terraces can be supported any number of ways: with gabions, interlocking retaining wall blocks, rockeries or slopes planted with shrubs and groundcovers with soil-retaining roots. To hold the soil in place while the plants are becoming established it is best to first lay erosion-control blankets or soil-saving biodegradable mesh.

Terraced areas help to hold run-off on a sloping site.
Image courtesy: juliantatlock.com

2. Berms and Swales

Often used in unison, berms (raised areas) and swales (shallow depressions) help to slow and capture run-off, holding rainwater so that it can gradually filter into the soil. Long swales planted with trees are ideal in large gardens where the soil drains well. They can also be used to redirect heavy run-off and simultaneously slow water flow, especially when constructed at an angle to the run-off flow and planted with lawn. Furrows and raised soil circles established around the drip lines of trees and shrubs do much the same thing.

Berms and swales retain run-off, allowing it to slowly filter into beds.
Image courtesy: biodiverseed.com

3. Build a French Drain

Basically a trench filled with rock or gravel, or containing a perforated pipe, a French drain is used to redirect surface- and groundwater away from an area. A long French drain built 2 to 5m from your property’s boundary and planted with a border, vegetable garden or orchard is a good solution if heavy run-off occurs at the lowest section of your plot of land. Run-off from your neighbour’s property can be harvested in the same way.

A French drain is ideal for collecting and re-routing sub-surface water.
Image courtesy: sunriselandscapeanddesign.com

4. Create a wetland, pond or bog garden

A wetland or bog is an area that is covered with water for extended periods and is able to support plant communities that live in water or waterlogged soil. Together with ponds, these aquatic-based landscaping features will not only enhance the aesthetics of your garden but also provide a great solution for the lowest part of a sloping property. Run-off is best directed to them by means of a French drain with piping or berms and swales.

A boggy area can be converted into a charming garden feature.
Image courtesy: ultimatechristoph.com

5. Look to the soil

Soil that is enriched with organic matter absorbs many times its own weight in water, which is then available for plant growth. It provides other benefits too: clay soils with added organic matter will accept water more quickly and organically amended sandy soils hold water longer and don’t, therefore, need to be watered as frequently. One of the easiest ways to build organic matter into your soil is to add compost, but worm castings, vegetable scraps, mulches, lawn clippings and leaves will also do the trick.

Organically enriched soil has a superior water-retaining capacity.
Image courtesy: gardeninginfozone.com

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