Free talk on rainwater collection

Free talk on rainwater collection

If you live in the San Diego area, you might be interested in attending a talk I’ll be giving in two weeks on rainwater collection. Should’ve done this two weeks ago, I know. Feels like we’re getting our entire winter’s worth of rain right now. Above is what my rain gauge collected in the last three days, and there’s more on the way.

The talk is free; I’ll be doing it as a UCCE Master Gardener volunteer. It’s on Saturday, February 4, 2017 at 1:30 pm at the Del Mar branch of the San Diego County public library.

I’ll be sharing reasons for rainwater collection as well as my experiences with different methods for collection and use in the garden. I’ll show lots of photos. In addition, I’ll talk a bit about using graywater (reusing household water).

Rain makes dreams come true

Rain makes dreams come true

This morning I awoke to the sound of rain. It’s the most pleasant sound, a muffled pecking on the roof. This is the first storm in a series of four that the National Weather Service says will give us three to six inches by Tuesday, an event with more potential to flood than anything we’ve seen since 2010, before the drought started. (Will this be the first year since then that we have above average rainfall too?)

I am possessive of my rain. See, I just did it — “my” rain. If I’m home while it’s coming down, then I’m outside running around checking levels on the tanks, adjusting hoses, observing the mulched basins I’ve built, getting soaked. My goal is that every raindrop sinks into the soil on my property — that not a single drop runs off my property.

I’m not there yet. I still lose some from the driveway, whose curb I need to make more cuts in. But elsewhere I capture it all. I refuse to treat rain like sewage.

How can we lament the drought and demand watering restrictions only to discard rain into the streets?

Recently, I cut a downspout pipe that channeled rain from one section of my roof directly to the street. It used to be that the rainwater gushed out of that pipe and eroded the soil at the edge of my yard and then carved a gully out of our dirt road and then flowed downhill to add to our neighbors’ flooding problems. So I unearthed that pipe and chopped it.

For one, that rain is mine. I’m going to keep it. For two, that erosion and flooding is my fault and I need to knock it off.

When my wife and I were looking for a house to buy we dreamed of having a yard large enough that would allow me to grow much of our food, and we also dreamed of having a creek running through the property. But creeks are extremely rare in Southern California, and alas we moved into this house and left our dreams of a creek behind.

Below our house the yard slopes down at about 5 degrees. One day after chopping the downspout pipe, I put our two sons in a wagon and told them we needed to collect rocks to make a river bed. Cass liked the idea of “making a river.” The boys and I tossed rocks into the wagon and then I towed them back to the place where I’d chopped off the downspout pipe. At the opening of the pipe they eagerly helped me lay a path of rocks — some yard work is meant for young boys, and carrying and tossing rocks is one of them.

“We made a river!” I said.

Well, we had made a bed for a tiny creek. Cass didn’t call me out on it.

Our creek is very short and it is not perennial; it only runs during a rain. But an ephemeral creek is better than none, and it’s better than erosion, and it’s better than flooding our neighbors, and it helps sink “our” rain into our yard. Better yet, it sinks the rainwater between some of our fruit trees, and I imagine the trees’ roots will eventually tap our creek’s flow.

Our creek is flowing this morning. And it looks like it will continue for the next week straight. Rain is making our little dream come true.

A new year, a new rain tank, a new weather pattern

It’s January 2016, and according to plan, we’ve got a new rain tank for the new year.


Our idea has been to install one new tank each year and make improvements wherever possible regarding the size, location, and distribution of the collected rainwater.

We got some things right with the first tank we put in last year, and so have imitated those aspects. They include the tank size, base, and location. This second tank is sized to handle just under four inches of rainfall on its section of roof (865 gallons of capacity for 552 square feet). This tank rests on a slightly raised base of gravel. And the tank is located where it can gravity-feed trees nearby, that is, the tank is close to a number of trees and it is above them in elevation.

There’s really only one thing that I tried with the first tank but abandoned, and that is distributing the water through driplines to nearby avocado trees. The primary benefit of applying rainwater to avocado trees is to leach the salts in the soil. However, water applied through drip emitters is ineffective at this because the water forms a chimney that dives mostly straight down but doesn’t spread laterally very much, thereby not leaching outside of the vertical chimney below the emitter. This is how it goes in my sandy loam soil anyway. So, I’ve learned to distribute the rainwater to avocado trees through a rain wand at the end of a hose, manually. It’s time-consuming, but at least it’s highly effective at distributing the water across the entire root zone of the tree.

On the other side of that coin, I have learned that I can effectively distribute the rainwater from the tank through driplines to most every other plant, vegetables, deciduous, and citrus trees included.

This is why I’ve set up the new rain tank the way I eventually set up the first rain tank: It has two connections where one goes to a hose with a rain wand for the avocados and the other goes to a dripline for vegetables and other fruit trees. Using non-pressure compensating drip emitters allows the rainwater from the tank to be distributed throughout those driplines by gravity alone.

And finally we’re predicted to get some rain! I installed the new tank in December, actually, but that was a dry month. We only got 1.2 inches. Now meteorologists are getting excited by a change in weather patterns. As the California Weather Blog mentions, there is a stream of significant storms finally aimed straight at Southern California. As I write, the first sprinkles are falling. The latest forecast shows precipitation every day for the next five days. The National Weather Service predicts we will have received between two and three inches of rain by the end of the week. The new tank will hold that just fine.

El Nino is not rain, and it doesn’t “come” to California

There seems to be a lot of misunderstanding about El Nino among us non-meteorologists. Here are two examples from Sunset magazine’s November 2015 issue:

“Before El Nino rears up this winter as predicted, here are easy ways to ready your garden for rainfall.”

And, “Because no matter how impatient we Westerners are for El Nino to arrive, the ensuing gray, gloomy weather might eventually feel a bit, well, gloomy.”

El Nino is not something that might “rear up,” and it is not going to “arrive” here in the American West, ever.

Why? What is El Nino?

I guess an official definition would be one given by the National Weather Service. They say, “El Nino refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific.”

That’s all El Nino is: relatively warm ocean water down near Peru.

That warm ocean water ends up affecting the nearby atmosphere and weather patterns, and then weather patterns around the globe, but those related effects are related effects and not El Nino itself.

So, El Nino is not rain, and more than that, El Nino is already “here.” That is, the condition of that certain part of the Pacific Ocean being warmer than normal has already been met.

What may or may not arrive in Southern California are the heavy rains that are sometimes related to that warm equatorial ocean water. And if they do arrive, then we will be having heavy rain that is possibly, partially caused by El Nino; we will not be experiencing the “arrival” of El Nino.

Sizing rain tank #2

I just picked up our new rain tank from the Bushman factory, and I chose to size it like our first one because that one worked very well last year. (I suppose I got lucky in sizing that first one.) In other words, I chose a size that would hold between three and four inches of rainfall from its particular section of our roof.

Here are the numbers for our first tank, and then I’ll give the parallel numbers for our new one: The first one collects from a 363-square foot section of roof. Four inches of rain on that area equals 872 gallons (363 x 4 x 0.623), but the roof is made of cement tile, and that surface absorbs some of the rain. Some people estimate cement tile to shed 65% of the rain that falls on it. My experience has shown that to be about right. So, four inches of rain on 363 square feet of cement tile roof sheds 567 gallons. Our tank has a capacity of 530 gallons — almost enough to hold that four inches worth of rain.

As for our second tank, it will collect from a 552-square foot section of roof. On this area, a four-inch rain would amount to 1,376 gallons but would shed 894 gallons. The second tank has a capacity of 865 gallons.


Bushman 865-gallon, waiting to be installed.

Why has the first tank — with a capacity to hold between three and four inches of rainfall — worked well? It has to do with how much rain we get and when we get it. Our average annual rainfall is 16 inches, but the wettest three months are what’s important. In January, February, and March, we average around 3.5 inches of rain each month. You might think the tank would fill up by the end of January and then just overflow all February and March; however, what usually happens is that we get a dry spell, often accompanied by warm Santa Ana winds, between the rain storms. Sometimes the dry spell lasts three or four weeks, even in these wettest months. And during these dry spells the collected rain in the tank gets used, at least in part, such that there’s room to collect more rain when the next storm comes.

For example, last winter (2014-2015) the 530-gallon tank was nearly at full capacity after a relatively wet December but then got depleted during a relatively dry January.

Our rain does occasionally come in the form of a four-inch downpour though, or a back-to-back couple of weeks of rainstorms in February that leave us with many inches at once. Here the tank is going to overflow. But this will happen rarely and momentarily. We’ve had one such single downpour in the past two years (February 2014) and no back-to-back rainstorms (though I expect some during this El Nino winter). True, if the tank were bigger it would be able to handle these rare deluges, but it would also rarely use its capacity, and that to me seems a larger waste.

A capacity of between three and four inches is big enough to rarely overflow yet small enough to have little empty space through the normal wet winter months.