how much water does our garden need?
July 16, 2013 6:22 AM   Subscribe

My wife is an avid gardener with a permaculture bent. We have a 1/3 acre suburban lot. Of our available gardening area, 1/3 is lawn which we do not water, 1/3 is stuff that we do not water. 1/3 is dwarf fruit trees, berry bushes, raised beds, vegetables, fig tree, a variety of plants. How can I understand what an appropriate amount of watering is needed for this amount of garden?

What I am noticing is our water bill going up every summer, so we are up now to an all time high of 23k gallons for 32 days. Where we used to see some summer dips in our utility bill, now the water component of our bill is going up so our total bill is remaining high year round (heating costs in winter, water costs in summer).
I think my wife is over watering. We've installed some drip irrigation for raised beds in our back yard. Since it's new I'm not totally sure it isn't leaking somewhere along the system.
Everywhere else, it's drag a hose and let her rip with soaker hoses and watering heads of various sorts.
From what I see, my wife will water for a solid hour or more for trees and other areas. I think she overdoes it. I'd like to be able to get a better understanding of how much water we need to apply so we're not simply applying water to the ground and wasting it or flooding plants in a way they don't really need.
posted by diode to Home & Garden (13 answers total) 2 users marked this as a favorite
I think there are too many variables here to give you a simple "you need X gallons of water every Y days!" What is your soil type, what is your climate, how much sun do your plants get, what are the moisture needs of your various plants, etc.? However, unless it's very hot and dry where you are, I'm guessing that an hour of watering every day is overkill. You could purchase a soil moisture meter (looks like they're inexpensive on Amazon) to give you some better data. Also, consider a rain barrel--free water! (if you get enough rain where you are to fill one up, that is).
posted by Empidonax at 6:40 AM on July 16, 2013

We don't know where you live (climate), what the soil is like, how many plants and trees you have, or how often you're watering them, but that does sound like an awful lot of water. Do you or your wife ever dig into the soil to see whether it's already moist below the surface, or is the watering just an automatic routine? Do plants ever wilt?

Not what you're asking, but if your water bill includes a separate sewer charge that's proportionate to your water consumption then you might be able to save some money by installing a separate water meter for the hose. Many water utilities allow a separate garden meter connected only to outdoor hose bibs, because it doesn't make sense to pay sewage charges for water that's not going into the sewer.
posted by jon1270 at 6:42 AM on July 16, 2013

Do you have swales in your garden? Swales will help water your trees, both with natural rainfall and by retaining your watering efforts and reducing runoff.

You need better mulch, better watering systems (ie, drip for the trees as well), or crops better suited to your climate.

23K gallons of water a month is insanity.
posted by lydhre at 6:43 AM on July 16, 2013

You've got a leak somewhere. Average water use is from 50-200 gallons a day per person. My house (on a 1/3 acre lot with 2 people) uses about 1000 gallons per month but we are pretty crazy about water conservation.

Trees need to be deep watered, and fruit trees use a lot of water, so I don't think she's in the wrong there. Soaker hoses and drip lines should be saving water not causing you to use more.

Seriously, 23k is a lot of water. Look for leaks and alert the water company.
posted by elsietheeel at 6:44 AM on July 16, 2013 [1 favorite]

I'm on 2 acres and I water my raised beds and fruit trees every day. In summer, our all time high water usage (without much conservation effort, in a house with 3 kids and 2 adults and the washing machine always going) is 4000 gallons.

You have a leak somewhere, and it may not be in your garden irrigation system.
posted by annathea at 7:02 AM on July 16, 2013 [3 favorites]

I, too, think you may have a leak somewhere. But, as to your question, you might be able to contact the local land-grant university extension office for some information about water needs. What you want to ask about is the evapotranspiration (ET) rate for your locality for the various crops you have. That's the amount of water lost through the combination of evaporation into the air and transpiration from the plant itself. Precipitation for your area minus the ET rate gives you the amount of extra water the plant needs. Each plant is liable to be a little different, but they should be able to give you some numbers that you can use to come up with a reasonable watering schedule.
posted by Shohn at 7:06 AM on July 16, 2013

Deep watering is usually best for things like trees etc as it encourages roots to go deeper and find their own water than to stay on the surface and so put the tree under more stress of regularly drying out. You can drip irrigate trees and in fact they are often better drip irrigated, this is done a lot in dry climates like Australia on trees and vines so you might want to look into it.

Look into if your sewer charge is tied into your water usage, I checked ours and luckily here they fix sewer charges in summer here to your average usage so you can water your garden and not pay extra for that too.

Your water usages sounds scarily excessive and I'd imagine you have a leak of some sort.

When we moved into our current house we used the black "leaking" hoses made out of old tires and they come with a gasket in them to reduce the water flow to the pip, this caused such a build up in water pressure in the pipes our ancient water pipes couldn't take it and we actually cracked a few of them flooding the basement (luckily we had a water alarm down there) among other problems. Strangely they only leak when we use certain taps so that might be why your bill is not super high all year around.
posted by wwax at 8:28 AM on July 16, 2013

Look up the Cooperative Extension Service in your area. They will have the expertise on watering, and will be delighted to share it with you and your wife. And she can get lots more great gardening info for your area from them. They are a really useful resource.
posted by theora55 at 10:09 AM on July 16, 2013

Response by poster: I was just looking at my bill. Last summer, for 32 days, my wife was away on an extended trip. We used 4k gallons and all seemed to be healthy and doing fine. This year, same time period, we used 23k.

It's of course possible there's a leak. Next step is to run some tests at night to read the meter when all is supposed to be off and see how it's working.

Thanks for all the tips.
posted by diode at 11:18 AM on July 16, 2013

That much water should cover 1/3 acre to the depth of 3 inches. That's a lot of water.
posted by blue_beetle at 11:36 AM on July 16, 2013

Not directly answering your question, but I suggest that in addition to checking for leaks etc, consider rainwater harvesting for the garden. We instituted this 4 years ago, and saw a marked drop in our water usage / bill. We didn't get fancy - a couple barrels at the bottom of downspouts, and watering cans. One of the downspouts has a fancier barrel which you can connect to a hose - but I'm afraid I dont remember where we got it.
posted by darsh at 12:11 PM on July 16, 2013

A drip system should give you all the information you need to determine how much water it's using: count the amount and size of emitters, and note the frequency and duration at which it's on. Emitters are color coded and/or specified by the manufacturer: for instance, 1/4" inline drip tubing is usually rated at 1 gallon per hour. If you're using some other kind of adjustable emitter like bubblers or shrub heads like this, these heads can put out a lot of water when fully open, some as much as 30 gallons per hour. If you have 20 of these things fully open for one hour, that's 600 gallons right there. So start there: find out what your system does and fine tune it. Since your wife is the permaculture gardener, this observation/learning/adjusting and reduction of waste should be right up her alley, as it conforms to like, six of the twelve permaculture principles.

As for the rest, there's no answer without knowing your soil, climate, plants in question, &c. For all I know you live on sand, and she needs to water the trees daily. However, aside from permaculture principles, plants generally do better with deep, infrequent watering. An hour may be what it takes- I need an hour to water all my houseplants. But it depends on how many hours a week she is watering, and more specifically how much water is going to the plants. If a bunch of it is running off because too much water is being put on at one time, she may need to spend a longer period watering more slowly. At any rate, 23,000 is an insane amount of water, and I'm surprised that your garden can thrive if that's really where it's all going. Fruit trees should not be watered if the soil is moist 4-6 inches deep around the dripline. Most raised beds do fine with twice a week watering. If plants must be watered more often, consider adding more compost and using mulch. A water meter that attaches to your hose or hose bib would allow you to keep records of usage.

Check for leaks first and foremost, and help your wife work out how much your drip system is putting out. Then devise some ways to conserve water use that are appropriate for your situation. A garden coach could be helpful for this. Using resources responsibly should be the goal of every serious gardener. I'm sure your wife wants to solve this problem as much as you do.
posted by oneirodynia at 5:05 PM on July 16, 2013 [1 favorite]

Response by poster: Thanks for all the information I received here. It seems as if we do not have a leak, just a highly overactive gardener with the garden hose.
posted by diode at 9:50 AM on August 17, 2013

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