There's been a subtle but noticeable shift in the subject matter of the outdoor-themed movies that visit us every year via Mountainfilm on Tour, the national arm of Telluride, Colo.'s Mountainfilm Festival.

Wildlife, beautiful landscapes and thrilling adventures like snowboarding and mountain climbing have always been blended with more ecology-minded short subjects.

In its fifth visit to Savannah, Jan. 17 and 18 at the Trustees Theater, Mountainfilm is almost exclusively represented by conservation films.

Not that they aren't also beautiful and thrilling; in fact, The Water Tower, a film by Colorado's Pete McBride, includes some of the most dazzling photography you're likely to see all year.

The Water Tower is the penultimate film on the Saturday evening schedule; after it screens, McBride will engage the audience in a Q&A session.

McBride's Chasing Water — filmed in Colorado — was a highlight of Mountainfilm 2011.

We spoke to the filmmaker this week.

You spent so much of your career as a nature and adventure photographer. Was there a big watershed moment when you decided to focus entirely on environmental work?

Pete McBride: I would say I've always cared, and there was a point where I cared enough that I wanted to focus my work more on environmental work. If I had to pinpoint, it. It would have to be the first time I saw the end of the Colorado River. When it turns into a kind of Frappuccino pit of muck and grime and garbage. I grew up there. To actually see firsthand that a river has run dry in my lifetime, hit me between my eyes like a 2x4.

Tell me why it looks like that.

Pete McBride: It ran to the sea for six million years, and it dried and hasn't reached the sea since 1998. It's basically over a combination of climate change, population growth and drought. And over-allocation. They all kind of met perfectly in the '80s and '90s, where demand completely out-stripped supply. And they mis-calculated the river flow; we once thought the river flowed X, now we know the river flowed three-quarters of X. But everyone drinks from X. It was very powerful to see that, in part because that river is so iconic and so beloved the world over.

Which brings us to your new film, The Water Tower.

Pete McBride: The Water Tower is about the changing watershed in Kenya. Interestingly, Kenya's at a stage where it's running out of its natural reservoir capacity, on equatorial Mount Kenya. And so they're going to head down the path of building dams. They're 50 years behind us; we've built all the dams and realized maybe that wasn't the solution.

But it also shows just how limited our water supplies are. Wherever you are. And how it's changing, with climate change and population and whatnot.

You say that 70 percent of Kenya's water comes from this mountain. Is the projection that 'You're damming this, and in X number of years your water will be compromised, or gone'?

Pete McBride: Well, they're still getting the same amount of water supply through precipitation, it's just not frozen. There once was a natural capacity for it to trickle and flow out consistently throughout the year. Now it's either there's no water, or it's a flood. There's no holding capacity on the mountain, so that's having rippling effects across the whole watershed. So when you get a big storm on the mountain, instead of it freezing and becoming part of the glacier, it just pours off the mountain, floods downstream and devastates areas. And then suddenly it's dry.