Solar panel systems can strain water resources.

Here's an angle I bet no one even considered.

A friend of mine is on the right track with automatic washing of the panels, but maybe at night.

And to cool the panels something probable needs to be done from the underside.  Like heat sinks or water/fluid cooling in a sealed system.

It looks like evaporation is not going to scale unless we are using sea water or gray water.
It's a complete waste to produce clean drinking water only to use for non-drinking purposes.


http://greeninc.blogs.nytimes.com/2009/09/30/solar-stirs-water-wars-in-the-west/

Solar Stirs Water Wars in the West

By Todd Woody

Isaac Brekken for The New York Times An irrigation riser at Ponderosa Dairies farm in Amargosa Valley, Nev.

As I write in an article in Wednesday’s Times, a water war is breaking out in the desert Southwest over the dozens of large-scale solar power plants planned for the region.
Depending on the technology used, some solar farms can consume more than a billion gallons of water a year in regions that receive three or four inches of rain annually.
It’s a truism that all water politics are local and that’s proving to be the case as solar power becomes the latest fight in the West’s long history of internecine water wars. For solar developers that means dealing with an often-bewildering array of regulations, stakeholders and politics.
In Arizona, for instance, plans for big solar farms have revived old fears that the desert state’s scarce water resources will be exported to energy-hungry California in the form of electricity.
“That has been an issue in the past and it will be come a political issue in the future,” said Kristin K. Mayes, chairman of the Arizona Corporation Commission, the state’s utility regulator. “I don’t think it will be an obstacle to the development of solar energy, but we have to pay attention and deploy solar technologies that use appropriate amounts of water.”
Across the border in Nevada, water politics are even more Byzantine. Individuals and companies own water rights separate from their property. If farmers and ranchers in California worry about big solar projects draining local aquifers, their counterparts across the state line are often eager to sell or lease their water rights to companies like Solar Millennium.

The German solar developer wants to build a 500-megawatt solar power plant complex in the arid Amargosa Valley west of Las Vegas. Its preferred method of cooling the twin solar farms would consume 1.3 billion gallons of water a year, about 20 percent of the desert valley’s water. To obtain rights to that water the company will have to negotiate with scores of local alfalfa farmers and companies.
At a public hearing in Las Vegas in August, environmentalists voiced concern about the impact of the Solar Millennium project on the endangered pupfish, a tiny blue-gray fish that survives only in few aquamarine desert pools fed by Amargosa Valley’s aquifer.
Then a weather-beaten gentleman dressed in blue jeans rose to fret about his future if he could not sell his water rights to Solar Millennium. Jim Marsh was not a down-and-out local alfalfa farmer, however, but the proprietor of a Las Vegas auto dealership. He also owns a casino in the Amargosa Valley and the associated water rights.
The Longstreet Inn and Casino sits off a desolate stretch of Highway 373. On an August afternoon, as temperatures approached 100 degrees, the slot machines sat silent in an empty gaming room while sprinklers arrayed on the perimeter of the property shot jets of water into the surrounding desert scrub.
Under Nevada law, property owners must use their water at least one year out of every five. “I’m pumping water out into the desert to keep my water rights,” said Mr. Marsh. “It’s absolutely ridiculous.”
Bill DeWitt is what you might call a fair-weather alfalfa farmer. He’s a Los Angeles real estate investor who bought up water rights in the Amargosa Valley years ago in anticipation of cashing in on the long-delayed nuclear waste repository at nearby Yucca Mountain.
Now he is considering leasing water rights to Solar Millennium. “We have a significant block of water rights we’ve been using in agricultural — growing alfalfa and hay and other things,” said Mr. DeWitt. “If it pencils out better for making megawatts, maybe that’s the direction to go.”