Tuesday, December 23, 2008

How Much Water Does a Man Need?

The first year I had my blueberries planted out in the traffic strip, there was no hose-powered watering solution for them. When they looked dry, I carried buckets out to keep them alive. I had other non-supplied beds where the same situation held.

Carrying water taught me how little water is actually required to garden if the water is carefully placed and not offered when not needed. By contrast, most of the watering I do is horribly wasteful: hundreds of gallons applied to soil not directly supporting a plant, lots of evaporation, etc. Using soaker hoses has improved my efficiency somewhat, but I need to get better at this and I know that I can.

Lots of factors determine how much water is enough. Planting things in the right place makes a big difference. Shade plants placed in sunny beds need much more water to survive. Accuracy of delivery (again) is a big factor. Time of day makes a difference due to evaporation. Ground cover makes a difference. Knowing your plants makes a difference. When fruiting, for example, things need and return the water supplied. When not fruiting, less water is required.

The simple answer to my opening question is: I don’t know. My goal, however, is to get to the point where I’m using about 200 gallons a day to water about 2000 square feet of garden. That’s about 0.16 inches of ‘rain’ per day or 58 inches per year raining constantly.

One way I have arrived at to check that goal for sustainability is to compare it with what we get from the sky naturally each year. In Eugene, annual rainfall is about 51 inches, not far from the 58 I’m shooting for. If I could simply capture rainwater, my system would be 100% sound. Because I cannot, however, and am aiming to ‘mine’ the water instead, I need some way to govern my mining efforts. 58 inches equivalent is a good start.

Apart from using rainfall as a check, there are practical reasons for keeping my water consumption number small. My micro-well plan requires above ground storage large enough to handle at least a day’s worth of water. If I use water inefficiently that volume goes up and the cost of the tank and the aesthetic impact, space requirements, pumping and power considerations, etc. all get uglier. A 200 gallon tank is only about 3 x 3 x 2. I can live with that.

(Apologies to Uncle Leo.)

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