A Facebook friend who works in agricultural recently posted this comment on her wall, "I just had someone write and tell me how appalled they are by learning how much water a pound of fruit or nuts requires."
I can imagine. In my experience, most city folk seem to think that peaches and walnuts just magically arrive, born of pixie dust and watered by dew. So yeah, it's a little shocking to learn that it took 142 gallons of water to produce your pound of peaches.
But the question that is not being answered - because it is never asked - is how much do these crops give back in water?
First of all, think for a moment about trees. Contemplate their size and age. They're going to be around for a while - in the case of peach trees, probably 40-60 years. You might be so lucky. The amount of water it takes to produce a pound of peaches also contributes to the health and longevity of the tree. This is a crop that does not need to be replanted every year. A well-tended orchard uses little in the way of chemical inputs, i.e. herbicides and pesticides. Weeds are usually just tilled under, and as trees are fairly hardy, pesticide dusting is reserved for the death star bugs that may cause total decimation, which doesn't happen every year.
Back to contemplating their size, trees are typically planted 20 feet apart in each direction. (That's the equivalent of three men lying head-to-toe.) Next, you should find out the average rainfall (in non-drought years) in the region of your target orchard, multiply that by the number of acres in the orchard to arrive at acre-feet of water (a sort of cubic measure of rainfall). After subtracting what the crop actually uses for one entire harvest cycle, you will find that there are probably hundreds of thousands, if not millions, of acre-feet of water going back into local aquifers and watersheds.
The same is true for salad crops like lettuce and celery, but when you are reading numbers about the amount of water it takes to grow lettuce or other salad crops, you need to multiply that amount x2 or x3. Why? Because those crops are rotated, reseeded, and regrown several times a year in the same place.
With peaches, if you are lucky, you may get 100 pounds of peaches per each 20 f00t square. At 140 trees per acre, that's roughly 14,000# of food per acre.
With lettuce, you may get 18,750# per acre, per year, after two organic plantings. That's also a lot of food. But because of the constant rotation, tractoring, harvesting and labor, there's more dust, and more inputs required. Up to 1,000 pounds of chicken manure alone may be applied per acre. That does not include other fertilizers, herbicides and pesticides applied on non-organic farms.
Unlike peaches, whose roots may be 16' to 30' deep, lettuce roots only go down a few inches. But unlike peaches, lettuce is grown shoulder-to-shoulder across wide swaths of soil and instead of pulling minerals and nutrients from deep in the soil, it depletes the top layers completely of both moisture and nutrients.
So if you want to bash one crop over another, you've got to look at more than the amount of water it takes to grow a peach versus a head of lettuce.
I'm going to leave it up to you to find the rainfall averages for your region, calculate the acre-feet of rainfall on say, a ten acre farm, and deduct a crop intake of water. All you need is Google, a calculator and two minutes.
I encourage you to do this because the point of the exercise is that you will irrefutably demonstrate to yourself that America's farms do not use water - they contribute both water and food! America's farms put water back into the aquifers that flush your toilet and water your lawn.
You might want to contemplate that the next time you flush your toilet - especially if you had peaches and lettuce for dinner.