The Earth’s surface is 70 percent water. But it’s hidden water that matters most to people who live on the Great Plains.

Between 1940 and 2000, Texas and Kansas headed a list of eight states that tap into this hidden water, which is found in the sand and gravel deposits of the Ogallala Aquifer.

During those years, Texas reduced its water reserves by 27 percent, Kansas by 16.

Some who attended a recent water conference in Lawrence weren’t worried about that. The conference was organized by the Kansas Geological Survey at Kansas University.

They spoke about western Kansas changing over to new crops. Farmers will abandon a water-hungry crop, corn, and move into less thirsty wheat, milo and sunflowers, they said.

Gary Hecox, who recently received a doctorate from KU in geology, discussed his predictions for the High Plains Aquifer. Afterward, he said, “You’re going to need grain a century from now. You might not need a corn-based agriculture.”

According to Hecox, if Sheridan and Sherman counties in northwest Kansas switched to milo and sunflowers, farmers could extend the aquifer’s life by 100 to 200 years.

If they don’t, his projections show irrigation pumps in those counties sucking air 40 years from now.

For those parts of Kansas blessed with surface water, the problem isn’t use but abuse.

Kyle Juracek, of the United States Geological Survey, talked about a study of 18 reservoirs in Kansas. In all 18, arsenic in the sediment exceeded the “threshold effects level.”

According to the EPA, that’s the point at which adverse biological effects are possible.

Copper in the sediment exceeded that level in 17 of the 18 reservoirs. The precise point of toxicity, or its cause, is unclear.

“Usually,” Juracek said, “you have several constituents — metals, trace elements, pesticides — and it’s hard to determine which one has an effect or whether it’s the combination.”

And that’s not all that contaminates surface water.

Paul Liechti, of the Kansas Biological Survey at KU, finds more fecal coliform bacteria in Clinton Lake than he’d like, more eroded sediments and more fertilizer. The last causes problems like algal bloom and fish kills.

As I see it, if we want to preserve the character of surface water or the volume of hidden water in Kansas, we have to overcome a huge problem.

There’s too little fear in the state.

I expressed my fear to a panel of reporters at the conference and asked what they thought. All write on water issues.

Each, by virtue of the contacts he or she makes, has a broader perspective on the issue than most of us.

Only Kelly Lenz, an agriculture reporter at WIBW Radio in Topeka, expressed optimism that the situation in western Kansas could be helped by moving to new crops that are less water dependent.

My problem with this hope is that the new crops are also less profitable. When does anybody ever volunteer to take a salary cut?

And even if farmers do accept smaller profits, doesn’t that mean fewer and fewer people can live in western Kansas — an area already threatened by population decline?

“I don’t see how small towns will survive,” Journal-World reporter Dave Ranney said.

“It’s hard to be optimistic without water,” said Jean Hays, of the Wichita Eagle.

The late, great naturalist Loren Eisely once wrote, “If there is magic on this planet, it is contained in water.”

Indeed, an infant’s body is 70 percent water.

When we mess with water, we mess with our essence.