Healthy rivers are the backbone of California’s ecosystems, communities, and economy—but understanding how they work, and what threatens them, is the first step toward protecting them. From the journey rivers take to the sea to the human decisions that shape their flow, this section breaks down the science, history, and policies that define California’s waterways. Explore the topics below to build your knowledge and become a more effective river advocate.
California’s rivers and streams stretch more than 180,000 miles, flowing from alpine headwaters to coastal estuaries and sustaining thousands of species along the way. The Sacramento River, the state’s longest, travels over 400 miles, while countless smaller waterways provide drinking water, habitat, recreation, and cultural connection for millions of people. These rivers tell the story of California itself—and learning how they function, connect, and recover is the first step toward keeping them healthy for generations to come.