It's not light reading, but if you want to understand water in Hawai'i, there is probably no better source than a new book published by the University of Hawai'i Press: "Hydrology of the Hawaiian Islands," by L. Stephen Lau and the late John F. Mink.

You might think water's pretty simple. It rains, some of it flows to the sea in streams and some soaks into the ground to form the groundwater that our water department wells tap.

But it's way more than that. And it's important in a state where a number of our drinking water wells are going salty and others are contaminated, some of our streams have run dry due in part to diversions, and the courts oversee towering battles over access to water.

The authors say they've tried to make as much of the book simple and clear enough for the "interested lay reader," but they concede that they weren't able to avoid some deeper scientific stuff that many of us will find difficult. Important parts are quite understandable and very informative.

Because geology is fundamental to how water moves through the islands, there's an update on our rock foundations and what happens when moisture falls on them. There are discussions of streams and coastlines, evaporation and things we inject into the ground—like wastewater. There's weather. There's how the mountains and valleys affect rainfall.

You wonder whether anywhere but the Big Island has climates within a few miles of each other that include hot desert, tropical monsoons and near glacial temperatures — thanks in part to the shape of the volcanic island.

How does water flow through different kinds of rock? What temperature is it? (On O'ahu, groundwater comes up at about 70 degrees.)

There are discussions of the pollution of groundwater by chemicals — often agricultural chemicals — used on the surface. Pollutants keep moving, and drilling deeper underground doesn't protect a community, the authors say.

"Great depth to the water table alone is not a guaranteed barrier to all contaminants; instead, it merely requires a longer transport time," they write.

While there are effective ways of remediating, for instance, pesticide-contaminated water, the authors argue that trying to repair the damage after pollution of groundwater has occurred cannot be a community's only strategy.

"Prevention is fundamental and involves regulatory actions and land management," they write.

You can find the 274-page hardcover, at $59, at www.uhpress.hawaii.edu.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766 or jant@honoluluadvertiser.com. Or call him at (808) 245-3074.