Ecological Design Blog

Rainwater Harvesting System Installed At San Diego Elementary School

5/7/2017

This past week we were very excited to install a rainwater collection system at Birney Elementary School in University Heights, San Diego, CA. It included a 300 gallon ferrocement cistern (Model LFC-300) that we hand-made at our shop and then assembled on site. The catchment area is a large multi-classroom roof so they will get lots of rainwater to use for their school garden!

Birney Elementary school garden

School gardens are extremely effective for experientially teaching kids about natural history and ecology, nutrition, water cycles, carbon cycles, soil ecology, and food cycles - not to mention what good food should taste like! They also teach kids environmental stewardship, foster a connection with nature and build practical skills. Having a rainwater harvesting tank adds an additional observable element to the garden letting kids actually see what is happening with water on site. It also saves the school money by using less water and reducing demand on stormwater drainage systems.

School garden water tank. Copyright Permasystems

Ferrocement water tank adjacent to school garden

The rainwater from the tank will be used to water trees and plants in the garden. A garden hose attachment makes is easy to move the water around using only gravity. The tank is light proof so no algae can grow, letting water be stored as long as needed. The tank and all parts of it are potable grade to provide the highest quality water. A first-flush device (#2 in photo below) allows the first few gallons from a rain event to be diverted from the tank and back to the drain ensuring the tank water is extra clean for plants.

Rainwater harvesting tank parts. Copyright Permasystems

The kids are planning to hand paint the tank - something you can only do with cement tanks. Plastic and metal tanks flex too much so the paint would flake off. We look forward to teaching the kids about water and rainwater harvesting in upcoming classes!

Remember, just 1 inch of rain over 1000 square foot of roof equals 600 gallons of water!

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Where Does Your Water Come From - San Diego County

3/27/2017

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Map of San Diego County

Here in San Diego County, we have a highly diverse range in climates, in fact, we are the most biologically diverse county in the country. From the oceanic coast, to the rolling foothills, to the tall mountains, to the expansive desert - the one thing the whole County has in common is we import the VAST majority of our water.

San Diego County Approximate Annual Rainfall. Copyright Permasystems

San Diego County - Inches

When trying to calculate our water supply, we should first start with what we have locally. Above we see the general range in rainfall amounts across the county. If we look below, we see that 16% of our water is from local supply. This includes surface water, groundwater, recycled water and conservation. This amount could jump up significantly if we embraced rainwater harvesting on a large-scale. Learn more how much we could be catching on our Catching Rainwater page. Additionally, water recycling and greywater systems both have HUGE potential for using water MUCH more efficiently, we will discuss these in future blogs.

Next we see that about 20% of our water is imported from northern California. This source relies on the Sierra snow pack, something that has been shrinking over recent years, see the report for details. The snow pack is important because it is like a bank account of water that can be relied upon into summer as it melts and flows down to the delta where the water is collected and exported to us. Unfortunately, even in non-drought years when the Sierras get a healthy snow pack, rising temperatures are melting the snow much faster than previous years causing us and many others to loose that critical time-released water.

All-American Canal. Copyright Permsystems

Southern California Water Canal. Copyright Permasystems

By far, the largest portion of our water comes from the Colorado River, about 64%. This water is obtained by the San Diego County Water Authority through a long-term water conservation and transfer agreement with the Imperial Irrigation District and two canal-lining agreements that transfer conserved water to San Diego County. Moving water over these long distances has significant costs and liabilities.

For one, 20% of out entries state's electricity is used to move water, that is a lot of money and energy each year! Secondly, having most of our water come from one source a long way away means that our supply is quite fragile. An earthquake or other disaster could quickly cut off this supply. Third, so many places draw water from the Colorado River, complicated and outdated water laws are creating tension between regions. Lastly, taking away such a significant amount of water from the river means that animals, plants and people down the river don't get any water. Other than a few wet years, according to University of Arizona,the Colorado River has not flowed to the Gulf of California since 1960.

20% of our ENTIRE state's energy is used to move water!

It is clear that relying on such a high percentage of foreign water is not sustainable in the long run. Through water conservation, water recycling and rainwater harvesting, both active and passive (described in upcoming blog), we can become FAR more self sufficient as a county.

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Harvesting Lots Of Rainwater Is Easy - Even In Dryland Environments (Like San Diego County)!

3/6/2016

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The hardest part of our business is getting word out that anyone with a house can catch thousands and thousands of gallons of water every year, even with the relatively low rainfall of San Diego County.

A standard 32 gallon trashcan can fill up within hours or even minutes when it is raining. Try it sometime and see how fast it goes!

The average home in San Diego County is approximately 2000 square feet.
The mathematical equation for rainwater harvesting is this:

For every inch of rain on 1000 square feet of roof equals 600 gallons of water!

That means the average house (2000 square feet of roof) in San Diego County, with our average of approximately 10 inches of rain per year, can catch 12,000 gallons of water off of their roof alone!!!

There is so much potential, even in drought years, you just need to have a place to store the water - like one of our ferrocement water tanks. Then, when your plants get thirsty you have the water on hand to give them a drink!

The key is to have a big enough tank, or multiple tanks, to store enough water that comes off of your roof. Take a look at the demand of your landscaping - do you have plants that need a lot of water, trees that need only a little in the summer, succulents, flowers, etc.?? We can help you understand your demand to help you better choose what size tank(s) best fits your home's needs. We offer free in-home consultations for new customers!

Check out the water flow from one of our tanks!

The key to remember is even YOU can catch, store and use thousands of gallons of water, saving you money, reducing demand of imported water and help the planet by using the tools in ecological design.

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Rainwater Harvesting System Installed At San Diego Elementary School

Where Does Your Water Come From - San Diego County

Harvesting Lots Of Rainwater Is Easy - Even In Dryland Environments (Like San Diego County)!

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