Making it rain

I first heard of shooting silver iodide into the atmosphere to make it rain in China, and it didn't seem like the sort of technology that could sustainably help with water shortage (the water in the atmosphere has to come from somewhere, right?). But apparently one Idaho utility has found tangible benefits at scale:

Idaho Power, which generates much of its electricity from dams, has been using cloud seeding since 2003, at a cost of about $850,000 per year for its main program in the Payette River area, officials there said.

“We’ve found our targeting to be good, and we’ve found precipitation increases in the 7 to 9 percent range during years that were very much less than normal snowpack years,” said Shaun Parkinson, who leads the utility’s cloud seeding project and is considering expanding it.

Idaho Power believes that in the winter of 2007, its weather modification efforts added enough water to the Payette and Snake Rivers to provide an additional 50,000 megawatt-hours of electricity at one of its major hydropower complex – the equivalent of a year’s power for nearly 4,000 homes.

Nevada has just stripped rain-making from its budget, but other Western states are still pursuing it. I'm at a loss to explain scientifically why "conservation of water" doesn't make this an unsustainable solution, but clearly some people buy the empirical results.

Apparently there is still skepticism in the scientific community over weather rain-making works, but in my non-scientific and anecdotal experience, the technology definitely works.