Is installing a cistern worth the trouble?
July 27, 2015 1:27 PM   Subscribe

We recently bought a 3 acre property near Ojai, CA. Over the next few years we will be building some new structures and rebuild the existing house. The land used to be an Apricot orchard but has been barren for decades. All the vegetation left are some beautiful Californian Oaks and two Olive trees. In May we planted the perimeter with 171 drought tolerant trees and bushes and have put a drip irrigation system on it (currently 1 X 30 min per week). This should take care of our privacy and hide the fence.

Between the house - garage - guest house and porches I expect about 5000 sqft of roof that we can collect water from. Historically our area should receive about 20" of rain between October and March. Almost nothing for the rest of the year.

Based on these historical averages (hoping the current drought stops...) we could collect 60.000 gallons of water (600 gallon per 1000sqft per 1" rain) witch would require a huge tank.

We have no plans to become farmers, but do want to plant some fruit trees and a small vegetable garden. The rest will be bushes and possible a meadow of wild flowers and/or lavender to cover the unsightly dust and weeds.

Here is my question: how much water do we need assuming we plant and irrigate responsibly?
posted by Mac-Expert to Home & Garden (20 answers total) 3 users marked this as a favorite
This is really difficult to answer without knowing a lot more details. How big of a vegetable garden to you plan to plant? How many and what kind of fruit trees?

A good starting point would be to figure out how much water you are using currently for your perimeter. What size of drip emitters do you use and how many are there?
posted by ssg at 1:38 PM on July 27, 2015

But the short answer is that unless you are planning a very small garden and only a few fruit trees (and you are only using a little bit of water on the perimeter), you will probably use up your entire cistern before the fall.
posted by ssg at 1:44 PM on July 27, 2015

Response by poster: The vegetable garden will be just a small raised bed enough for 2 people.
Fruit trees a couple of apple, orange, lemon trees. For consumption and decoration.

There is no historical data. This is a blank slate.... See our website to get an idea...
posted by Mac-Expert at 1:46 PM on July 27, 2015

This guide is for colorado, but you can calculate how much water you might need based on the type of crop, and your soil type. There is also a lot of information in that about small acreage irrigation in general! You may want to contact the southern california university extension offices to see if any of the ag schools put out something california specific.

You can find your soil type here.
posted by cakebatter at 1:47 PM on July 27, 2015

If by 'worth it' you mean, will the cost of the cistern be lower than the cost of paying for tap water, then the answer will almost always be no. I live in California too, and I did a quick analysis for my house. I estimated that it would take about 100 years for it to pay for itself. That is because what we pay for water is so so so damn cheap compared to everything else.

Now, there are other reasons to build a cistern (less energy to import and treat water, using water close to the source) but it will almost never be saving money.
posted by chevyvan at 2:10 PM on July 27, 2015

How do you get your water? Municipal? Well? Surface spring? Do you have water rights?

Get a meter, and find out how much you are spending on that drip irrigation. If you are on an unmetered water system now(private well), get a meter onto it for your own use.

Come at the problem from the cost of storing up to that much water. While it won't answer questions about how much you need, perhaps the numbers alone will convince you not to.

It's a 10x20x40 foot cistern, and there is a cost in constructing that, and a footprint, and a location, and engineering costs, permitting costs, and aesthetic concerns with placement.

Or it's 12 5000 gallon tanks (try using the plastic ones), with a cost and a footprint, and some locations, engineering costs, (fewer) permitting costs, and (great) aesthetic concerns. There's a sweet spot with regard to tank size/cost per gallon, I suspect.

Note also that your domestic water use will come to something like 20K gallons a year (probably more, for normal people), and much of that can be used on your landscape.
posted by the Real Dan at 2:16 PM on July 27, 2015

Best answer: New trees need something like 25 gallons a week for the first three years. I think the controlling factor is how much you're willing to spend for storage cisterns. Prices quickly climb into four figures as the capacity increases.
posted by ob1quixote at 2:23 PM on July 27, 2015

Response by poster: Thanks for all the great feedback!

We are on municipal water and currently use on average 50 gallon per day including the irrigation for the perimeter plants.

Well drilling company told us that the water is at least 800ft deep @$10 per foot its not an option..

I am torn about making cold calculations about cost for cistern vs using potable water to irrigate plants. But there is a limit between environmentally friendly and reality...
A big cistern thing could easily add up to to a lot of money. A couple of above ground tanks are easy to install but still add up to $4000 - $5000 for a total of "just" 10.000 gallons of storage. And I have no idea how far this could take us.

For sure we will be installing grey water system in the new construction.
posted by Mac-Expert at 2:29 PM on July 27, 2015

Using cisterns for all your runoff water may be more than you can manage, although could use them for a start. So you might want to consider building a pond that would hold the 600K gallons plus probably another 600K, including whatever runoff you can gather from the surrounding land. For situations like this, it would be good to put in a stepped bottom on one side such that when the water recedes you will still have easy access to the edge. This pond can be planted with water plants and stocked with fish, to provide another yield for you.

One positive thing about collecting seasonal water is that your soil biology is harmed by watering it with chlorinated water. There are bacteria and mycelium that promote plant health and nutrition, and contribute to the nutrition of plants growing there, so this water would be far superior to your piped-in variety for your trees and your garden. Also, if you treat it for human consumption with a few drops of bleach, you will have an emergency supply in case your piped-in water gets interrupted somehow, by accident or earthquake.

Another thing- in case you are threatened by wildfire, the pond is a place for the fire trucks to pump water from, and could save your house.

By running your greywater through a gravel treatment bed, you can harvest water from washing and collect that in the pond as well. (For greywater, I think the size needed is six cubic feet of gravel bed per person in the household.)

Water for trees can be stored underground in swales, mulch-filled ditches which catch and absorb water in rainy seasons and release it during dry times. With a little strategic landscaping, you can conduct runoff water downhill through any swales that become saturated and into your pond to provide water for the trees in the summer.

These are some techniques I have been studying lately. Permaculture is a set of practices that among other things, makes the best use of what water and other resources you have already. You may want to consult a local certified permaculture designer to get some more suggestions on what would work on your site.
posted by halhurst at 3:00 PM on July 27, 2015 [3 favorites]

Response by poster: Great idea to create a pond. I could keep the water moving by pumping it uphill and let it run back to the pond trough gravel / pant beds to filter and oxidate it. Plus keep the mosquitos at bay.

My only concern is that the pond might evaporate quickly during the summer when there is no rain at all..
posted by Mac-Expert at 3:14 PM on July 27, 2015

If moving pond water uphill is too much work, these windmills are specifically made for aerating ponds, assuming you have the wind available to drive then.
posted by jquinby at 3:19 PM on July 27, 2015

Response by poster: Yep I had a classic american wind mill in mind. The stream will also create an esthetic element to the landscape ;-)
posted by Mac-Expert at 3:28 PM on July 27, 2015

Off topic, but: New trees need something like 25 gallons a week for the first three years.

I am a California horticulturalist. You could kill your drought tolerant young trees by watering them as much as this guide for Washington DC recommends. You also won't encourage them to root deeply- important for helping to prevent stress in times of drought. Here's a much better guide. You need to do some digging around in your soil to see how much water is getting into it, and how long it's sticking around in order to fine tune your irrigation. If you're watering via drip, you're going to need to make sure that the emitters are in a ring around the dripline of the tree. Deep, infrequent watering is best.
posted by oneirodynia at 4:03 PM on July 27, 2015 [3 favorites]

Response by poster: Thanks, yes we are not over watering our drought tolerant perimeter plans. Already weaning them from 3 x per week for 10 minutes to once a week for 30 minutes and will continue watering less frequent once they get settled.

The more I think about it the less sense it makes to catch & store large amounts of rain water. Better conserve and reuse (grey) water.
posted by Mac-Expert at 4:27 PM on July 27, 2015

Well, consider this, California just turned off their free beach showers. There is a lot more they may regulate. Holding on to cistern water may be the water you get if firefighters pump an area dry, or something else happens. If you can keep some water and plan to depend on your agricultural output, then good.
posted by Oyéah at 4:49 PM on July 27, 2015

Water restrictions. Water pricing. Restrictions on dams/bores. We have all three here aimed at conserving the water assets, and they are likely to intensify/spread, as weather patterns change.

It will probably never be cheaper to invest in infrastructure, and you get to use it straight away. Water tanks, bores, pumps, reticulation, gray water treatment and reuse, other water conservation measures - do it right the first time, do it with an eye on the future (especially both availability and price of bought water, and possible restrictions on bores).
posted by GeeEmm at 7:13 PM on July 27, 2015

Unable to read the names of the plants on your landscape plan - are the plants CA natives? If so they should need little if any additional watering once they're established. If they're CA native plants you'll have the added bonus of providing habitat for native birds and insects. The good folks at Las Pilitas nursery recommend micro spray rather than drip irrigation for CA native plants. It uses the same amount of water but distributes the water in a more natural rainfall pattern.

A smaller capacity catchment system combined with efficient use of gray water should allow you to have a reasonable size orchard and garden.
posted by X4ster at 9:20 PM on July 27, 2015

I saw someone mention this upthread but the rallying cry of "Extention!" does not seem to have been taken up. Are you familiar with this resource? Here is a list of CA offices by county. Call yours!
posted by DarlingBri at 4:58 AM on July 28, 2015 [1 favorite]

Response by poster: Most perimeter plants are Australian and South African plants that are supposed to be very hardy and drought tolerant. They are doing great in this area. Once established they should hardly need any irrigation :-)
posted by Mac-Expert at 7:39 AM on July 28, 2015

Response by poster: OK this is ridiculous and easy....

I just went to the website of our water company Casitas Water converted the max size cistern we could will with an average annual rain fall (60k Gallons = 80 units) and found that this would cost us only $189.92 to fill...
And this is the most expensive residential rate...

I don't want to be a cold blooded bean counter but I cant justify spending thousands of dollars on building a cistern. No matter what size it doesn't make sense :-/

The best thing we can do plant drought tolerant and irrigate very selectively to avoid waste...
posted by Mac-Expert at 9:00 AM on July 28, 2015

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