A watershed is an area of land where all the water that drains off of it collects in the same place, often a river. The communities in the service area of the Waterwise Community Center and Chino Basin Water Conservation District are part of the Santa Ana River Watershed because all the water that runs off the urban and natural areas in those communities eventually collects in local creeks, all of which join the Santa Ana River near the Prado Flood Control Basin. The Santa Ana River Watershed also includes portions of Riverside and Orange Counties, and a small part of eastern Los Angeles County. It is a 2,840 square mile area that has a population of over 6 million people.
The total length of the Santa Ana River and the streams that drain into it is approximately 700 miles. This network of waterways, whether natural or channelized in concrete, connects the water across all the communities of the watershed. The health of these waterways and conditions of the urban and wild areas that drain into them have major impacts on water quality, water supply, and habitat for native plant and animal communities.