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  • From: Road's End Farm <organic87 AT frontiernet.net>
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] How do you irrigate?
  • Date: Mon, 15 Mar 2010 12:30:23 -0400


On Mar 15, 2010, at 8:13 AM, Garth & Kim Travis wrote:

Greetings,
I am confused, it has a well for the house and is only 7 acres. So why
would you need another well? We have 20 acres and 1 well, that does the
job. You probably just need to run some pipes.


Alliums wrote:

I’m looking at a 7 acre property that doesn’t have a water source 
(unusual in Southeastern PA). It has a well for the house, but nothing 
else. Should we dig another well for irrigation? Should we gather the 
water that flows to the bottom of the property into a pond? 


There may not be anywhere near enough water coming into the house well to irrigate 7 acres. There may not even be enough water coming into the house well to irrigate a kitchen garden for the household. I have neighbors slightly downhill from me who have three wells, and during long dry spells they need to have water hauled in so they can take a shower. My well will supply the household, but produces only about ten gallons per minute when the weather has been wet enough so the groundwater supply is good, and much less than that if the weather has been dry for some time; this in an area where some others less than a mile away have more than enough water to run 100 cow dairies and irrigate large market gardens in addition -- and there is a huge lake less than a mile from me. It all depends on the way the water is moving underground, which, around here, is highly variable.

It's not possible, in this area, to just keep drilling deeper: there are salt beds as part of the bedrock layers, and drilling too deep is extremely likely to bring up water far too salty to either drink or irrigate with.

In addition, not all properties will produce a good irrigation pond. If the soil's not deep enough or not otherwise suitable, it may not be possible to build a deep enough pond, or it may only be possible with the use of very expensive lining techniques. If there's not enough water on the property to keep the pond full, and there is no underground spring to fill it, the pond may run out during long dry spells (this is the situation that I'm dealing with). What looks like a lot of water at the bottom of the property in March may not be anywhere near enough water in a dry August.

Having said all that: the property in question may have lots of water (maybe you've got a well as good as Kim's!); but you do need to find out. Your county Soils and Water should be able to tell you whether the property is likely to produce a good irrigation pond, and also something about how much water you're likely to be able to get from the well; also whether drilling additional wells will accomplish anything other than maybe dividing the available water between them, and/or messing up your neighbors' water supply. I'd double check that with well drillers and pond builders who have both significant experience in the area and good reputations. It should also be possible to test the existing well for output, although again, the output may or may not be consistent through the year; so bear in mind that you'll be testing it at a time when the available water is probably highest. -- You can, and should, do all of this before buying the property; either do it before you put in a bid, or put in a bid that specifically states it's contingent on your being able to find as much water as you need. 

-- One acre-inch of water is 27,154 gallons. If you want to be able to irrigate all 7 acres at once (which you might not, as some of it might be in cover crop or fallow rotation at any given time), you'd need about 190,000 gallons per week, or about 20 gallons per minute from a source capable of producing that 24/7 for possibly several weeks straight (many sources that will supply 20 gallons a minute can't keep up that rate all week, or even all day). You could reduce the amount needed by using drip irrigation, laid out so you only irrigate the actual root zone of the crop and not paths or areas between beds or rows.

Oh yes: also get the household well water tested for quality! Coliform and lead at a minimum, and check with Soils and Water as to what else you need to check for -- salts, nitrates, and/or atrazine, for instance, may be an issue in some locations. It's astonishing what's in some household wells without the owners being aware of it -- even if they're roaringly healthy, that may be because their systems have adjusted to the local bacteria. Some problems with well water quality may be easily repairable -- there might just be a surface crack in the casing -- but others aren't.

-- Rivka; Finger Lakes NY, Zone 5 mostly
Fresh-market organic produce, small scale






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