California's Watersheds

Why is it so important for Californians that the Sierra Nevada Mountains have snow on them?  Students may have witnessed first hand – or certainly through the media – the bleak picture in the Sierras this spring.  Snowpack is at an alarming 5% of average – the lowest snowpack ever recorded. So what will this mean for Californians throughout the coming dry season? Here are a few key points to consider about the role of the Sierra Nevada Mountains in California’s hydrological system:

  •  Sierra snowpack supplies more than 60% of the state’s developed water
  •  Snowpack and meadows in the Sierras provide natural water storage
  •  Forests and meadows in the Sierras help ensure a high water quality
  •  Close to 50% of water flow into the Delta originates in the Sierras (and the Delta provides  drinking water for more than 20 million people and irrigates 3 million acres of agricultural land)[1]

The Sierra Nevada Mountains are California’s primary watershed and enable the state to grow half of the nation’s fruits, vegetables, and nuts, prodigious amounts of dairy milk, and sustain the largest population and economy of any state. An exceptional drought, as we are in right now, calls into question the extent to which California can continue to lead the nation on these fronts.

Students (and everyone) will benefit from a greater understanding of California’s watersheds, and how they sustain the people, crops, animals, and businesses that inhabit this state. The Nature Conservancy provides a very helpful tool for investigating local watersheds. Students can type in their zip code and learn exactly where their water comes from through maps and text. These maps explain the land use in each watershed as well, and by comparing numerous locations throughout the state, students can begin to see just how complex California’s hydrological system is.

The map below illustrates how available water is moved throughout the state to supply drinking and irrigation needs. Note that this map does not reflect the current drought conditions.

CA watershed diagram

Map from, Your Source of Water Additional Resource.