Water, water, not quite everywhere

When I was a kid I was “born again,” a process that involved being fully and totally immersed in water. Much more recently I was on the home stretch of an 8-mile walk in the hot sun when the minister I was walking with kindly poured her drinking water on my hot little head.

Seldom does water feel so good as when splashed on an overheating noggin in the summertime. As soon as my hair was sopping wet, I certainly felt born anew, able to complete the walk with at least a tiny smidgen of spring in my step. Just a cup or two of water, supplied at the crucial time and applied to best advantage, made all the difference in the world.

What would you imagine is the largest use of water in the U.S.? We all can guess it’s not drinking water itself, nor wetting the heads of aging geologists. Would it be what goes on everyday in kitchens for meal preparation? Or the weekly washing of laundry? Bathrooms and what we do in them? Perhaps commercial carwashes use more water than your home?

Actually, irrigation makes up the most significant use of freshwater in the U.S. In a nutshell, some farmers use a lot of water to grow crops on semi-arid or marginal land. Techniques range from flooding fields to using pressurized sprinklers to anoint crops with much needed artificial rain.

There are some significant drawbacks to irrigation. Freshwater is a precious resource and using so much of it for farming can be criticized as profligate. Beyond that, irrigation can degrade soil, making it saltier over time as water evaporates repeatedly in hot and dry regions where irrigation is commonly practiced.

But there are two major ideas to keep in mind when it comes to irrigation. The first is that around the world irrigation truly helps us produce food for the 7 billion mouths we now have to feed on the planet.

In various parts of the U.S., we irrigate to grow everything from vegetables to wheat and rice. Almost all states in the Union have some measure of irrigated agriculture within them. And, as most of us vaguely know but don’t often articulate, American farmers feed us well and also produce enough for many millions of others around the world to whom our harvests are exported.

All those facts came to mind recently when I read of a University of Wisconsin study about irrigation on the global scale. The bottom line of the study is that global irrigation patterns increase farming output substantially. In fact, that increase is almost as great as all of U.S. farming output rolled into one sum – and we grow a lot of food in this country, so that ain’t nothing to sneeze at.

Agricultural productivity and irrigation isn’t the same everywhere because a little bit of water in a dry field can increase yields much more than more water in a wetter region. Interestingly, the Wisconsin researchers believe irrigation around the world is used close to maximum efficiency.

In some ways the efficiency of global irrigation is good news – we humans are not being wasteful with respect to a very large chunk of our freshwater resources. But it also means that as population continues to increase, we can’t feed more mouths just by upping our irrigation efficiency.

One reason scientists and engineers are studying matters like irrigation is that people have become interested in all forms of carbon uptake from the air. If you grow plants, they “mine” carbon dioxide out of the air to build their carbon-rich little selves. A tree locks up this carbon for years or even centuries to come. By comparison, a crop plant like wheat only temporarily stores carbon.

Freshwater is one resource that, like energy, goes into all sorts of our products and activities. It’s so much cheaper than gasoline, we normally don’t think of it as we go about our daily lives. But it’s a limited resource, the use of which has significant environmental impact. What we want to do with it is something we could well afford to think about more clearly.

One thing is evident to me: I want us to always have enough water to pour over the heads of old ladies taking long walks on hot summer mornings.

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University. Peters can be reached at epeters@wsu.edu.