Community Garden Exchange

Who knew that so much functionality could look so pretty!

Yesterday a group of enthusiastic volunteers installed a “Rainwater Harvesting garden” at our Community Garden site.

The Way it Was

For those of you reading this from other areas and other states, here in Southern California we get no rain — ZERO — each year from about May to November. Thus everything we plant needs to have an irrigation source. We had an area outside the garden gates where we wanted to grow citrus trees, but it didn’t have proper irrigation.

Then a participant at one of the Environmental Change-Makers‘ “Life After Oil” sessions noticed a nearby downspout from the roof of Classroom 5. The downspout had been designed in conventional style to empty into a driveway so that its annual water bounty was directed away to the storm drains and whisked “away” into the Pacific Ocean.

Realize that here in Los Angeles, the water which comes out the hose at our Community Garden has been imported from miles away. Some of it comes from the hotly contested Colorado River. Some of it comes from the parched Owens River Valley. Some of it comes from the Sacramento Delta area via the State Water Project, which is similarly undergoing contractual debates. We have maxed-out our water resources in California, yet we continue with an attitude of waste.

Meanwhile, pumping and processing water demands 19% of California’s electricity. Much of that electricity is derived from coal, with accompanying greenhouse gas emissions. Thus saving water in California is also a global warming solution!

So in the original version, we were treating our annual rainwater bounty as a waste product, and at the same time, we were importing water over great distances at high environmental and social cost.

A glimpse of the possibilities

There are two downspouts from Classrooms 2 through 4 which pour into the Garden site. Prior to the Garden installation, these downspouts emptied onto the old lawn. During our garden design phase, one observer wryly noted “it’ll be riparian part of the year.” In other words, we had to solve the problem of those displaced downspouts before the rainy season in order to prevent flooding.

In the original design for our Garden, we’d dreamed of adding rainwater harvesting tanks. Perhaps you’ve seen the small (55 gallon) versions in garden catalogs. We were looking at large 620 gallon tanks, and beginning the fundraising journey.

Meanwhile, several of us had recently been exposed to the ideas of Brad Lancaster. Lancaster is in Tucson, AZ, where he works with far less water than we have in Los Angeles. He has designed and installed beautiful gardens watered by rain. We’d seen photographs in his recent presentation in Santa Monica, and we’d poured over the detailed diagrams in his books.

Lancaster points out that we can save rainwater in many ways. Rainwater harvesting tanks and cisterns are one way. But we can save far more rainwater (at far less cost!) by saving it in our soils. Called “infiltration,” we simply design our garden grading (the shape and form of the land) to retain and soak up the rain, rather than designing our grading to send water “away.”

We could do some relatively simple things at our garden and make the most of our annual winter bounty. We could ease the burden we were putting on city infrastructure, and the demand our garden made on regional water supplies.

By bringing more water to our soils, we would help replenish our groundwater supplies, and reduce the amount of stormwater dumped into the ocean. As we capture more moisture deep in our soils, we encourage our trees to grow deeper root systems, which helps them be more drought-tolerant through our dry months, and we boost the soil moisture for our living soils.

The Planning

We wanted to plant four dwarf fruit trees: a Valencia orange and three tangerines. As dwarfs, these trees should grow to approximately 10-12 feet, and can be shaped and pruned as they grow. The goal was to have the trees’ foliage merge one-into-the-other, for an evergreen hedge which bears food.

John Tikotsky, a landscape architect, had been attending some of our Environmental Change-Makers and Community Garden events. He had also seen Brad Lancaster’s Santa Monica presentation. John and Joanne worked together on the plans for our South Citrus area.

John estimated the roof surface of Classroom 5 — actually, half of Classroom 5. Classroom 5 has a classic pitched roof. We observed that the downspout in question captures the rain from peak to eave — only a small segment of the total roof space at Holy Nativity. John estimated this at 394 square feet.

Joanne popped this estimate into a handy online rainwater calculator. In an average year, our area gets 11 to 14 inches of rain. Thus we could possibly harvest as much as 3400 gallons of water!

Our South Citrus site has a slight slope. To slow and spread the water from the downspout, we decided on a series of berms and mulch pits. Berms would keep the water on the area, and mulch pits would cause the water to soak in. The mulch and rock would serve to hold the channels and pits open for water, by holding back the soil. We selected several diagrams from Brad Lancaster’s book and decided to build them.

If you have Lancaster’s Volume 2, the pages we selected were Fig 3.13 (page 98) for surface aesthetic, Fig 2.5B (page 69) for berms, and Fig 1.16B (page 54) for spillways.

From Joanne’s observations and experience with our sandy-textured soil, she knew that our berms would quickly erode and become flattened. We decided to add vertical plastic pieces inside our berms for the purpose of helping our berms retain their structure. John found us a plastic product that was designed as a tree root barrier. It came in a roll and was about 12″ wide. Because it was flexible, we could curve the tree root barrier into “S” and “J” and “U” shapes, just perfect for our unique application.

See our design here: plan view (from above, as if seen from an airplane) or section view (as if we cut a slice through the project). We’ve taken the approach that this is an “experimental” installation — that it’s okay to rethink and “tweak” portions of the design as we observe how they work.

Installation day

About 15 volunteers joined us. We opened the day with a garden class, discussing “Why save rainwater” (see above) and “Do we have enough rainwater to save”. We talked about our attitudes about water, and various methods of saving it. See “Water Wisdom” for much of the content.

Then we moved to the Garden and got to work.

First, we dug the three mulch pits. Since the area had already been rototilled and compost had been added, we took care to save the amended topsoil. When it came to removing soil material from the site, we removed the deeper, harder packed soil, rather than “the good stuff.” In all, we removed perhaps 3 wheelbarrow-fulls. Some of this will go into immediate use elsewhere on the garden site. The remainder will be available for use in our biodynamic composting operation.

As the mulch pits reached desired depth (perhaps 24-30 inches), we dug spillways between the pits. The spillways were about 12″ deep. We had to take care to keep the spillways continuing downhill — at the shallower depth it was possible to get them headed uphill!

We lined the spillways with rocks. The donated rocks were approximately 8″ in diameter. We used the flatter ones to form the bottom and sides of the spillway. Peter worried that people would trip and fall if we left the spillways open like we’d originally planned, thus we put the rounder rocks down the center of the course.

Next, we installed the plastic root barrier. Volunteers held it in place as others backfilled the mulch pits. The mulch created pressure to one side of the plastic, while the soil berm created pressure at the other.

John had cut donated plastic sewer pipe to direct the bottom of the downspout into the new spillways and pits.

We planted the new trees, and created mini-berms on the downhill side to catch and hold water. We will need to hand-water our new baby trees between now and the time the first rains come, and these mini-berms will help hold the water where the new trees need it.

We also planted a few drought-tolerant perennial flowers (fortnight lilies and Salvia leucantha) to eventually hide the drain pipe. These species should flower abundantly, while being tolerant of the intense heat that radiates off the nearby blacktop.

If you’re in Los Angeles, stop by and see our Rainwater Harvesting garden — we hope it will inspire you and give you confidence to try one too!

This entry was posted on Sunday, October 26th, 2008 at 11:09 am and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.