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.)

Water From The Sun

Another part of the overall water solution I’m getting interested in involves a solar-powered micro well. The basic wet-dry season pattern I mentioned earlier also happily coincided with the availability of sun. Sun is strongest when water is most needed. Why not use the sun to move water?

So, I started looking into solar powered micro well options. Surprise! They do indeed exist. For about $1700, I can get a very small DC powered submersible pump with enough head to easily reach our shallow water table. Another $1000 or so will buy me a couple of solar panels to mount on the roof of my bee shelter to power the pump. A few hundred more will go to a small elevated storage tank that will have enough head (pressure) to reach all of my gardens.

The micro-well strategy once again raises a basic economic question about the cost of sustainability. In simple financial terms, it’d take a great many months of water bills at city rates to justify the $4000-$5000 I expect my water solution will cost. As with many other aspects of this garden effort, simply getting setup to be more sustainable is expensive. Cheaper ‘conventional’ options exist. Whether you’re talking about building a swale versus simply piping to the street, installing solar water heater, solar PV power, or whatever, cost of installation can be considerable.

After no small amount of consideration, I’ve landed on three basic ways of viewing this dilemma. First, many conventional solutions involve costs that are either hidden or that have been completely ‘externalized’, that is, shifted onto somebody else’s balance sheet. Second, I simply ‘do the math’ as a means of translating daunting up-front costs into daily terms which I can then more readily weigh against the myriad other small things I spend money on daily. The third perspective I’ve come to is more philosophical: keeping all costs local (e.g. taking responsibility for them personally) helps me keep focus on what’s really sustainable and helps me more directly understand the how much I personally cost the planet.

Frankly, my current city water solution has few hidden or externalized costs I can identify which might help me craft better math in support of the micro-well initiative. By contrast, doing the math reveals that the investment required to be nearly water independent (even in town!) is very modest when expressed in daily terms. Assuming a ten year service life for the well and an initial investment of $5K, my daily costs are about $1.30. (That number assumes no interest…actually a conservative estimate in today’s economic environment!)

So, the basic question comes down to a cup of coffee a day versus water independence. I can deal with that.The remaining challenge I have is to get the city to OK the well. More on that point later…

Keeping Water

A few years ago I learned that in decades past a small stream had flowed down from the hill to the east and through the lot on its way down to the still small, but larger, Amazon Creek. This made sense to me in light of the sheer amount of water that ‘wanted’ to be on the lot, sometimes in awkward places.

So, my original plan was to restore at least the contours of the old creek as a means of re-enabling better drainage which would in turn allow for earlier gardening, better management of storm runoff, etc.

However, my permaculture friends have convinced me to explore a different basic strategy for water which uses contour-line bed as a means of actually holding as much water on the lot as possible. Rather than reinstating creek bed across contour lines, I now plan to use drainage swales between beds, running parallel to contour lines as a means of managing water. The primary objective behind this strategy is water storage.

In southern Oregon, we basically have a sort of mild monsoon climate. From a precipitation point of view there are more or less two seasons: a wet one beginning from November to May and a dry one from June to October. My own water bill reflects this pattern almost perfectly: my water bill for any one month between July and September equals the total water bill for all other months between November and June. Most of that water is used for gardening. So, again, water storage is an important challenge.

I considered cistern or tank based storage of water. However, each time I did the calculations, I ran into the fact that storage of significant quantities of water requires significant space….a problem for my small lot and for my interest in density. Engineered approaches to the space problem also get expensive (or ugly) very quickly. Putting tanks in the ground or above the ground is difficult.

Soil, however, has a remarkable ability to hold water. So, I began looking at ways of keeping more water in the ground itself. That opened my ears to the suggestions of the ‘permaculturistas’ to consider contour-based beds and swales.

The swale system is not a complete solution. Surface soil still dries out. It’s also not an instant solution. Hydration of a piece of ground can take years, just as desiccation of a piece of ground or a watershed often occurs over decades. However, specifically for a garden plan based significantly upon perennials (e.g. permaculture), it holds promise. Perennials typically have deeper roots able to stretch down to find sub-surface moisture. Perennials also create shade that can conserve surface water for annuals.In the net, the ground level of the lot is going to rise a bit owing to my sheet mulching approach to bed building. This higher ground and the pathing I install in the swales will still enable me to move about in the garden without swimmies even during the wettest parts of the year…that’s the plan anyhow.