You can’t see them. You can’t swim in them. But groundwater aquifers are one of the most important sources of water in the North Coast. Aquifers are water-rich underground areas. They aren’t like lakes or pools but are composed of water-filled areas between rocks, sands and gravels. Plants and animals benefit from groundwater when it’s near the surface, and feeds creeks and streams. Humans tap into aquifers through wells used for drinking, irrigating crops and operating businesses. People who live in rural areas rely almost exclusively on groundwater, and while cities in Sonoma County get most of their water from the Russian River, groundwater provides a critical back-up source that is used during droughts or in emergencies.