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Deliberately flooding the swales

 
Ann Torrence
steward
Posts: 1191
Location: Torrey, UT; 6,840'/2085m; 7.5" precip; 125 frost-free days
110
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I'm in the 4th day of an interesting experiment. A year ago, we dug 3 swales across our 3 acre property. They are probably too deep and too narrow for our summer rains, but they are what they are. They have had two surprising benefits. First, they catch, hold and melt snow that otherwise would evaporate away. Second, they let us "get ahead," to use the local vernacular, when there is a surplus of water in the irrigation canal.

The main canal, which was hand-dug in the 1890s, is filled from a high mountain reservoir from the first Saturday in April to November 1. For most of that period, I get to water on a schedule on every 11th day for 12 hours. But in the early spring when the run-off is high and the late fall, there is more water and the schedule is not so rigid. Awkward sociology of sharing notwithstanding, what people try to do is dump as much water in their fields to bank it through either the hot summer droughts of June until monsoons, or through winter. The previous owner of our parcel flooded the street at the bottom of the property more than once in the process. Hence the swales.

The water on this parcel comes in at one corner and the land slopes diagonally in a gradual way about 6 feet to the flooding corner. There's an ancient apricot tree at the flooding corner that we have not gotten water to since we took ownership, and yet it is thriving. The last surface water it had was maybe three years ago. We know that at least in summer, the water table is high from the irrigation around us, based on septic tanks our neighbors just down hill installed. I put a lot of stock into local custom, so maybe this "getting ahead" works to charge up the soil to carry through the drier seasons.

Everybody else is growing alfalfa or using their land as horse pasture. The last hay has been baled up. When we switched over to free water, I sat back. I didn't argue for my turn (I much prefer the formal schedule to the negotiating on the fly). It's the end of the year, they are ready for the irrigation season to be over. So for the last few days, I have been taking all the water. I turn the water in as soon as I remember, watch it all day, and turn it off when the lowest swale overflows. The first time took about 24 hours, yesterday I shut it off after 10 hours because the third swale was overflowing. I certainly am getting far more water onto the land than was ever possible before the swales. No water is leaving the property. The real question is if water is holding in the growing zone or is it just sinking down 100s of feet? I think not, based on the lone apricot tree and some other ephemeral water features in my neighbors' pasture-ephemeral in that appear when he takes a lot of water. If I'm lucky, I'll get 2 more pulses through before they drain the canal on Saturday. It feels good to be able to use this resource to pull those new tree roots deeper where the surplus water can be stored. It's just not what you usually think of using a swale for.
 
R Scott
Posts: 3306
Location: Kansas Zone 6a
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Just like buying presents on December 26th. Lots of value if you can store it.

There are potential problems with overhydrating before a hard freeze, but I think the benefits outway any concerns--unless you start getting water in your basement or something.
 
Ann Torrence
steward
Posts: 1191
Location: Torrey, UT; 6,840'/2085m; 7.5" precip; 125 frost-free days
110
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R Scott wrote: There are potential problems with overhydrating before a hard freeze, but I think the benefits outway any concerns--unless you start getting water in your basement or something.

Please explain more about concerns for overhydrating before a freeze. It's already freezing here at night.
No basement to worry about, this parcel has no structures Just need to keep it off the county road. Last time the previous owner turned it into a mudpie and it took forever for the county to get out and regrade it.
 
brad millar
Posts: 99
Location: Menifee, CA
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It's just not what you usually think of using a swale for.

I thought that was the primary purpose of a swale. (slow it, spread it, soak it)
 
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