Approximately 40 percent of California's surface water supply originates from the snowpack in the Sierra Nevada Mountains. However, climate change is significantly altering this precious water source. With this diagram and accompanying lesson from Clue into Climate, produced by KQED, students will learn about California's historical average snowpack through 1990. Students will also examine how the snowpack is expected to change if temperatures reach the lower end of the predicted warming range by the end of the century.