Photo of the Sweetwater River channel, dry in Chula Vista during the 3-year drought experienced in 1958 through 1960. The Sweetwater River is 55 miles long, the largest river flowing into San Diego Bay. From its headwaters high in the Cuyamaca Mountains, the river flows generally southwest, first through rugged rural areas but then into the urban areas surrounding its mouth at San Diego Bay. The watershed has a human population of over 300,000 residing in Chula Vista, National City, Bonita and Rancho San Diego.