Monday, 9 September 2013

A Better Rainwater Harvesting Solution

I first heard about this solution about 10 years ago while trying to find a better solution to deal with the fact that we funnel all our rainwater off site one day, and then irrigate our gardens using municipal water the next day.
Arum lilies make great plants for rainwater gardens
If we are really forward thinking, we use green solutions such as water tanks, in which we try to catch as much water from our roofs as possible, store it, and then pump it out into our gardens. This really is a great solution. But I'd like to suggest an even better option.

Our soils were created to be natural water tanks. Depending on their composition, they (like sponges) have the ability to catch and hold water. They catch hundreds of thousands of litres of water, releasing it slowly over a period of time, either upward to the roots of plants, sideways into rivers, or downward into the groundwater below. Good soil is essentially a reservoir for plants to survive through periods of dryness. So why do we funnel it off into tanks, or even worse let it drain away into the stormwater system?

Normal rainwater could be funnelled into the soil where it belongs, and excess water overflows into the stormwater system.
The answer to this problem is actually an age old one, and it lies in using plants, and in shaping the soil to slow down and catch the water.

Instead of using the downpipes to carry water straight into our stormwater system or at least into tanks, the water would flow from the roof down the drainpipes and into a catchment area with plants that would naturally be found in wetlands. These plants can tolerate both waterlogged and dry conditions depending on the season. The water can then drain away naturally into the soil.

Vancouver's innovative stormwater solution
Another application is alongside large paved areas, like parking lots, driveways and roads. The water that comes off these areas usually has a mixture of oils, litter, and other pollutants that end up in our rivers and eventually the sea, creating huge long term problems. We should be creating filtration areas before the water runs into any kind of stormwater system.

This can be a beautiful way of bordering or softening hard areas like parking lots and roads, and in a water thirsty country like ours is an ideal way of conserving water in the place where it should be conserved.
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