When I take my kids to visit their grandpa in rural Tulare County, they know the rules: Don't drink the water. Instead of pouring a glass from the tap, they pull a bottle from the fridge.

Welcome to life in the central San Joaquin Valley, where groundwater laced with nitrates and other contaminants is too often unfit for drinking, cooking and even bathing.

People used to debate about the source of nitrate pollution -- until last year's comprehensive University of California at Davis report (http://groundwaternitrate.ucdavis.edu/).

It clearly identified agriculture fertilizer and manure as the main contributors.

Lack of safe drinking water makes life hard for one-quarter of a million people in the Valley and Central Coast -- California's most profitable agricultural regions. In this land of overwhelming abundance, surrounded by orchards and verdant crops, rural families must add the cost and inconvenience of bottled water to their struggle to make ends meet.

We know about the problem and we know what causes it. Now we need to fix it.

A report released this week by the California Water Resources Control Board recommends a fertilizer fee as the most promising way to provide a reliable and stable funding source for safe drinking water.

California lawmakers are considering several bills designed to address groundwater contamination in the Valley and elsewhere. Most require new funding sources or seek to extend existing funding sources. A fertilizer fee would provide a much-needed stable and dedicated source of funding.

I trust no one will argue with me that every California community deserves access to safe drinking water. California taxpayers currently pay between $20 million and $36 million a year to provide safe drinking water for some affected communities.

Researchers at the UC Davis Center for Watershed Sciences estimate the annual cost to taxpayers to really address the problem will be closer to $100 million.

Should California taxpayers bear this burden? And if not, where should the money come from?

A fertilizer fee is an equitable way to make sure those whose activities contribute most to the problem are a major part of the solution.

That makes sense to me, and I'm guessing most Californians would agree that a fertilizer fee is a fair and reasonable solution. Now it's up to California lawmakers to make it happen.

The report by the California Water Resources Control Board provides the road map to a day when I can take my kids to visit their grandpa and not worry about the water, and when thousands of families can enjoy what most Californians currently take for granted: clean water from the tap.

When I was a kid, bottled water was a fact of life.

Now that I've spent time outside of the Valley, I understand that most Californians expect -- and get -- clean water when they turn on the faucet. Most Californians don't have to worry about teaching their kids to reach for a bottle -- and not a glass -- when they are thirsty. Nor should they.

With the California water board report, California lawmakers can move beyond debating whether there's a problem and what causes it, and instead focus on fixing it.

And they can fix it in a way that ensures those who contribute most to the problem are part of the solution.