On a stormy spring day, Devon Peña stood atop a sagebrush-covered hill and looked down on Colorado’s San Luis Valley. Dark clouds had unleashed a deluge just a few hours earlier, but now they hovered over the mountains, veiling the summits above. Below, rows of long, narrow fields extended from Culebra Creek toward a man-made channel, the main artery of the valley’s centuries-old “acequia” irrigation system. This was the “People’s Ditch,” a waterway holding the oldest continuous water right in Colorado. … The acequia system was once dismissed by Western water managers. But as a changing climate brings increasing drought and aridification to the Southwest, time-tested solutions like this one could hold the key to mitigating the worst impacts of climate change, especially in rural communities.