Watersheds change at a pace that often evades human perception. Millennia might as well be minutes and centuries seconds on the geologic timescales over which watersheds carve valleys, smooth mountains, and shape ecosystems. However, just because they have the power to reshape the world doesn’t mean watersheds are immune to human influence.

“The Platte River Basin is this 90,000-square-mile (234,000-square-kilometer) watershed that sits right in the heart of the North American continent,” says Michael Forsberg, a conservation photographer who has spent decades sharing stories from the Great Plains. As with much of the region, years of overuse and abuse have left an indelible mark on the watersheds here and their surrounding ecosystems. “Almost all of our rivers are really altered from their natural state,” says Mary Harner, an ecosystem ecologist at the University of Nebraska at Kearney. “And in many cases, we can never go back.”

In 2011, Forsberg started Platte Basin Timelapse, an ambitious project to document how the watershed has changed—and is changing—using dozens of strategically placed solar-powered cameras, from the headwaters in northern Colorado to where the watershed empties into the Missouri River in eastern Nebraska. Now, researchers across the Midwest are using the more than five million photos that have been captured to answer questions about what’s happening in the watershed and what can be done to reduce and, in some cases, reverse human impacts. “As scientists, we can’t be everywhere. We can’t go back in time. We can’t stand at a creek for days on end and watch it,” Harner says. “We miss so much. Imagery is a way to observe a place in timescales that is just not possible in other ways.”