One of the core services provided by the Department of water Resources is to monitor the state’s snow pack to predict annual runoff. The department uses multiple methods including taking remote readings from sensors high in the Sierra Nevadas called “snow pillows.” A number of those sensors need to be repaired and enhanced but it’s not an easy task. Crews had to trek into the Emigrant Wilderness on horseback 18 miles for just one sensor. … The trip took four days. And it made for epic photos, which DWR shared online. Here are just a few.