Water, Part 4: Save the Bay, Get It In The Ground

On previous posts I've touched on rainwater harvesting into tanks for later use. But another way to harvest rainwater is to put right back into the ground where it can replenish the groundwater and be stored for future use by landscaping. Typically we take that water falling from the sky and send it away as quickly as we can, wherever away may be, which in my case is the bay. This happens via downspouts, street gutters, and municipal drainage systems. But instead of sending that water "away", you can manage it locally and sink it back into your local soil where it will happily stay until it's needed by your plants, trees, etc. I've been planning on implementing this into my own property in a couple different ways and this year I got both methods up and running.

First is the rain off my roof and the rest of my property. I can't harvest all of into tanks, especially when you consider the total amount of rain falling on my property. Using some rough numbers of 5000 square feet of property and 24 inches of average annual rainfall we get 5 * 550 gallons/1000 square feet/inch of rainfall * 24 inches = 66,000 gallons of water! If I wanted to put it into a tank, I'd need a 20' diameter tank that's 28' tall. Yikes! But the ground can hold that no problem. So how do you capture it? With berms and swales.

A swale is the low side and the berm is the high side. We took the front yard and dug a swale parallel to the house and piled the dirt on the sidewalk side to make a berm. We filled the swale with wood chips and then we directed the downspouts to drain into that swale.

Here you can see one of the downspouts with a pipe extension to get it to the swale.

We're on a corner so the swale makes a 90-degree turn and runs parallel to the front of the house until it reaches the entry walkway.

This is a shorter piece between the walkway and the neighbors.

The second source of rainwater doesn't necessarily come from your property but from your neighbors and the street. Since we live on a corner, we have rain flow in the gutter that builds up to quite a large quantity by the time it reaches the street drain, which is old and can't always handle that much water. So using more formal examples that I've seen, we implemented a more guerrilla-style solution by cutting out the concrete at the concrete strip, excavating down a few inches, and then filling it with wood chips. Then to give the water a place to enter and exit, we made a couple curb cuts.

This is the entry cut. I'm still working on how to direct the water from the gutter into the parking strip. A lot of the water flows right by with entering the curb cut.

The minor excavation before the wood chips went in.

And the exit cut. I ended up using a piece of hardware cloth to keep the wood chips in and let the water out.

It looks like this should be a wet winter so I should have plenty of opportunity to observe and tinker to make sure things are working how I want. The front parking strip also needs a couple curb cuts but there are some additional challenges there. If this kind of thing interests you, I highly recommend Brad Lancaster's Rainwater Harvesting for Drylands and Beyond: Volume 1 for an intro and Volume 2 for a more detailed look at earthworks.

I'd also like to offer a special thanks to Christopher Shein of Wildheart Gardens for help with the earthwork and Kevin Jefferson of Urban Releaf for help with the concrete and curb cutting.