Viewed through the window of an airplane, the Colorado River just seems so unlikely. On a cross-country flight this New Year’s Day, I watched as the snow-covered Rockies gave way to pancaked expanses of red rock. At its headwaters in the mountain foothills, the Colorado makes sense. But as I watched it flow through the deep scars that its waters had carved into a desiccated landscape, the river felt strange.
As a native of drought-ridden Southern California, the Colorado River has always loomed large to me. It is the only game in town for much of the Southwest, irrigating farmland and flowing into city water supplies that allow tens of millions to call the desert home. Over the ages, the river has also played a central role in shaping the Southwest. Over millions of years it has cut through solid red rock to create the Grand Canyon and other spectacular landscapes. But how many millions? Just figuring out when the river began watering the Southwest has long puzzled