Cape Town is experiencing severe water shortages. Yet the City receives two to three times more water (rain) than its annual requirement, so where does it go? It runs off roads, paved areas and roofs and literally goes down the drain: into storm water pipes and out to sea.
While people are scrambling for tanks and boreholes, it seems we have forgotten the importance of infiltration: capturing water runoff and allowing it to seep into the ground. The soil is in fact our largest and least expensive ‘tank’, one that provides moisture to plants for weeks or even months after it has rained. Furthermore trees and shrubs are like living pumps: moving water from the ground, providing moisture and cooling the air – nature’s free air conditioning.
Rainwater harvesting can be done with simple earthworks – swales, berms, depressions, and other landforms – that capture and ‘plant’ the rain, instead of letting it run off the site. Earthworks serve to reduce erosion, and are a convenient passive form of irrigation that requires no tanks, mechanical pumps, valves or irrigation systems. They function whenever rain falls, and water flows – especially helpful on mountain slopes and for ‘oily’ or hydrophobic soils. Earthworks take some effort to install but require very little maintenance. They can be used anywhere – in public landscapes, gardens, schools, street planting, parks and farms. So let’s not waste this free water resource and ensure we maximize the potential of available rainfall.
For an excellent practical guide on how to create successful earthworks for rainwater harvesting consult Brad Lancaster’s ‘ Rainwater harvesting for drylands and beyond’ (www.harvestingrainwater.com). His advice is to start with long and thoughtful observation, and plan a small and simple intervention in the highest point of the property. The purpose is to slow down and spread the flow of water so that it can seep into the soil. Another important principle is to always plan the overflow route and manage surplus water as a resource. You can use earthworks, planting and mulch to create living sponge(s) in the landscape.
In summary the most logical, cost-effective strategy to maintain a garden or landscape is:
- FIRST harvest rainwater and runoff with appropriate earthworks so that it infiltrates the soil.
- Next set yourself a goal of zero storm water runoff: consider storing rainwater in tanks and treating for use in the house.
- Then consider treating and reusing your grey water in the landscape.
- Borehole water is a valuable but finite resource that is at risk of being depleted by an ever-growing number of well points and boreholes. Consider it as a last resort to be used under exceptional circumstances and e.g. for food gardens.
If you love gardening there is no need for big capital outlays, no waiting for plastic tanks, no fossil fuels required – just time honoured farmer’s logic. Rain is the highest quality source of irrigation water – all you need is careful observation, some planning and a spade to utilize it. So grab a spade, and start small and simple!
The stewardship path to abundance. This site passively hydrates itself by productively planting the rain with the on-site harvest and infiltration of rainwater and runoff. This reduces downslope flooding and water contamination. Grey water is directed to plants in times of no rain. Wells, creeks, and rivers are recharged. Leaf drop/mulch is also harvested and cycled back into the soil and plants, further increasing fertility and water-holding capacity.
Image & caption from Brad Lancaster’s www.harvestingrainwater.com