Guide to Water Conservation Garden Display

Water Conservation Gardening - Display by Heather Balcomb and Linda De Luca

Water Conservation Gardening is the wise use and management of any water in the garden, particularly rain water. Ideally our gardens should not let a drop of water leave our property - be it a home or business park, or shopping area.

We hope this display gives you visual inspiration on how to implement some principals of water conservation design in the gardens.

We have focused on rain water in this display, but please note that many of the principals can also include the  management of grey water in the garden.

The display includes:

  • A succulent garden that demonstrates how these beautiful, drought hardy plants can be used in a garden that is carefully planned to minimize water consumption and water loss.
  • A rain garden that illustrates:
  • The capture and storage of rain water, slowing it down on its rapid and often destructive path to our rivers
  • Methods of spreading it out in the garden to decrease erosion as well as to create more surface area to absorb it
  • Methods to assist with its infiltration into the ground
  • Elements of wildlife gardening to welcome our smaller co-dwellers to the garden

Rainscaping techniques

There are a number of techniques that can be employed for managing rain water:

  • Re-directing water from down-pipes
  • Collecting water in rain-water tanks or smaller barrels.
  • Creating berms and swales to slow run-off water down
  • Creating rain gardens to collect run-off rain water so that it can be absorbed.
  • Reducing impervious cover (e.g. using permeable pavers)
  • Creating green rooves (planted rooves)
  • Increasing the health, water retention capacity and permeability of your soil by adding compost, humus and mulch, and  grit or small pebbles.
  • Carefully considered use of indigenous plants  (especially naturally occurring plants)
  • Increasing the urban tree canopy to break the force of heavy rain showers.

Creating a rain water garden

Should be on a gentle downward slope, AWAY from the house.

  • Test soil quality for permeability. Dig a 50cm deep hole and fill with water, check how long it takes for the water to seep into the ground. If longer than 24 hours, add mulch, loam and river sand / grit to increase permeability.
  • The ideal shape is a tear drop - with the narrowest end nearest the flow of water, and the broad end furthest away.
  • Size should be in proportion to the area available and also the amount of water that needs to be trapped.
  • The top of the garden should be level, i.e. far end should be built up a little if needs be.
  • Cross section of the rain trap should be a gentle “u” shape, about 50 cm deep and width and length in proportion to the garden.
  • Fill the base of the basin (15 to 20cm) with gravel to aid drainage.

Plants to use

It makes sense to use locally available indigenous plants, as these will be most suited to the environmental conditions in your garden.

  • Beauty and functionality - it is very important that the garden is aesthetically pleasing to you, as well as working effectively to trap rain water.
  • Tolerate both ponding / saturation from rain water accumulation and drought.  Collected water should not stand for longer than about 24 hours
  • Creating wet and dry zones. Group plants so that they will thrive according to their water requirements.
  • Wildlife value. Locally indigenous plants will have the added value of being the natural food source for local wildlife.

Ensuring that rain water is slowed down naturally before it rushes into our rivers has a number of advantages:

If enough people in a neighbourhood do it we could actually contribute towards recharging the groundwater and thus raising our water table.

Plants and soil etc. that slow the run-off down also serve to filter out some pollutants including chemicals and trace metals.

Plants’ roots in particular can sustain various microbes that assist in bio-filtration, resulting in cleaner water being released into the environment.

The more water that soaks into the ground, the less water will enter the drainage system at any one time. It will be released gradually.  The positives to this are that nearby stream water quality can be improved.

River beds will not be scoured out as regularly, and aquatic biodiversity will be able to establish itself and thrive. The other advantage is that it prevents large scale erosion due to the force of water movement.

As water is a precious (and increasingly more expensive) resource we need to shift our gardening style to maximise the amount of water that is trapped on our properties with some relatively small changes.

By creating small berms, swales and dips one can slow water down sufficiently to ensure that most of it will soak into the ground, depending on the soil type. Some soil conditioning can greatly enhance the soil’s  capacity to absorb the water.

On a larger property or in a business park, Rain water depressions (rain gardens) could be created in a series down the slope, and be connected by swales or French drains so catch any overflow from one to the next..

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