by Jude Hsiang
We’ve had some welcome rainfall recently, but unfortunately, we in Central Maine are still in a drought, as is the rest of the state. We wonder how long this can continue, especially as fall is usually an excellent time to plant trees, shrubs, and perennials. Weather reports offer only a few days of reliable forecasts. While the science has become more sophisticated decade by decade, the changes in worldwide temperatures continue to effect wind patterns, making the predictions increasingly more challenging. We may not feel that we can expect much more clarity from the weathermen and women than our grandparents did.
We might not repeat the old weather sayings – “Red sun at night…” – with as much confidence as in the past, but we don’t have much trust in the constancy of our climate. While we wait and see, we might remember a few facts about weather and water we may have learned in our elementary school science books.
Our planet has all the water it has ever had, and likely ever will – a closed system. It’s position in the solar system has given it the nickname the Goldilocks Planet – not too hot, not too cold, just right for life. We look at the globe and easily agree that 70 percent of Earth is covered by water.
Other water facts can be harder to understand. Science tells us that 97 percent of that water covering the world is saltwater and almost all of the remaining 3 percent that is fresh is actually locked up in glaciers or deep underground. That appears to be changing, but calculations done over years conclude that only 0.4 percent is available for human use. An almost unimaginably tiny amount! A gallon of water – an amount I can understand well enough – equals 128 fluid ounces and 0.4 percent of that is about three teaspoons. So much depends on so little.
The average annual rainfall in Central Maine is about 42 inches, or about .8 inch per week. Of course, that rainfall is never evenly distributed over the weeks or the acreage, but it is generally enough to keep most plants, and other living things like us, healthy.
That not-quite-inch of rainfall will move about six inches down into the soil – the typical root plant’s root zone. Even the largest trees’ roots those that actively provide water and nutrients, are in the top six or so inches of the surface, while larger roots provide anchorage.
Gardeners are advised to water at the surface of the ground so the water can soak right down into the roots zone, and to do it just once a week, unless we’ve had an inch rainfall, as small amounts given more frequently may not get deep enough. (Of course, the newest, littlest, seedlings need attention appropriate to their baby status.) If you’ve set up a sprinkler, soaker hose, or drip system, you can dig down six inches occasionally to see if that water is penetrating nicely.
While we watch and wait impatiently for the drought to end, we can try to use the water we do have wisely.
© Judith Chute Hsiang
Jude Hsiang is a retired University Extension Master Gardener Program instructor and a member of the China Community Garden.
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