In this podcast we talk about how you can save the rain that falls on your property for use in the landscape.
Many people are sceptical about the benefits of harvesting rainwater. As an introduction, we would recommend these resources:
- Brad Lancaster is a hero of ours, and his books are a real inspiration
- Watch Geoff Lawton’s Greening the Desert video
- Listen to Neal Spackman on the Permaculture Voices podcast
- Watch TreePeople’s piece on rainwater harvesting
Reasons To Save Rainwater
How Much Water Can I Collect?
There is an easy calculation to determine how much water comes from your roof:
For a 1 inch rain event falling on a 1000 square foot of roof, you can collect 620 gallons of water.
Take a look at your own roof on Google Maps in satellite view, and use the measuring tool to work out, even just roughly, how big your roof is. The next step is to find out how many inches of rain per year you get where you are. Now multiply the size of your roof by the number of inches of rain and multiply by the conversion factor of 0.62. That’s how many gallons you could collect.
Rain barrels are a great first step when capturing rainwater, and they come in all shapes and sizes. 55 gallon or 75 gallon sizes are typical, but the flat one here is 120 gallons. Larger cisterns are also available. Rebates maybe available in your area.
Another option for collection of water is a rain water bladder. Great for emergency preparedness too.
If you do use a recycled food barrel you will need a kit that includes the spigot, overflow and any necessary hole saw bits.
If you want to join several together you can ‘daisy chain’ them using a kit of parts.
Here is a good example of a DIY rain barrels that have been daisy chained together.
The overflow of each rain barrel needs to be directed away from the foundations of the building, ideally into an area of the landscape where the soil has been converted into a healthy soil sponge.
For most of us, a rainwater harvesting system that captures all our rainwater is going to be prohibitive in terms of either cost or just practicality. This is where our soil becomes the biggest and most cost effective cistern available to us.
Another way to redirect rainwater into the landscape is to use a rain chain.
Here is a picture of the very simple set up I saw in a landscape in Carlsbad. The dew collected from the roof was directed into the small bucket via the bit of rain guttering hung from the roof. The homeowner told me that she typically captured half a bucket or so every few days, enough to keep her birdbath filled.
A similar process takes place with boulders, where the dew is directed around the base of the boulder, and the heat from the boulder also offers some protection for the plants.
‘Plant The Water’ – How To Create A Swale
A Swale is a ditch on the contour. It does not direct water, but holds it and allows it to gradually infiltrate the soil down-slope of it. The important thing to remember here is that it really does not have to be very deep. Just a slight slope – 1/4 inch per foot – is enough to have water drain down hill. Flat areas within the swale allow the water to sit for a bit and sink into the soil. A healthy soil sponge will absorb much more water than compacted dirt.
How big does that swale need to be?
A very rough rule of thumb is for every 1000 square feet of catchment area (roof, driveway or other hard surface) you will need about 100 square feet of landscape at a depth of 10”. If you can find 200 square feet, you only need to go to a depth of 5″.
Quick fix for swales that is too compacted to drain
Our best advice for a swale that is too compacted to drain is to drill into the soil using an auger bit and fill the holes with worm castings. You will want to drill about 8-10 holes for each square foot of ground. Then top the surface off with fresh tree trimmings or mulch that has been partially composted. We used this technique on a project we were involved in at a public park and it worked like a charm.
Mosquitos love to breed in standing water, and this is often the first concern homeowners have about rain barrels. Fortunately most modern rain barrels have fine mesh covering all openings to stop the insects getting in there to lay their eggs. If you are making your own rain barrel it is important to make sure that your design includes this feature. While you are out in the garden, check for drip trays, wheel barrows or pots that could collect water, and put them upside down or under cover.
Cobble In Swales Or Rain Gardens?
As a contractor I installed lots of ‘dry stream beds’ filled with gravel and cobble. Now that I know better, I realize that if we want water to sink into the ground, the soil needs to be ‘fluffy’ or ‘friable’. Putting down gravel or cobble (especially over weed barrier or landscaping fabric) creates compacted soil that will not absorb water. Use cobble or boulders to slow the water down, or take out the energy of water falling from a roof line, or entering a swale from a curb cut, but leave most of the soil open and uncompacted. And don't forget the vital role that plants play in the ecosystem that is healthy soil - the plants feed the microbes that keep the soil healthy and able to absorb the water.