Another tributary, Laguna Creek, flows northwards from Woodside with its source on Edgewood County Park and Natural Preserve, and historically fed Laguna Grande and then joined San Mateo Creek just upstream from Crystal Springs Canyon, where San Mateo Creek turned east to flow through the canyon. Laguna Grande was submerged when an earthen dam (this was the first Crystal Springs Dam) was constructed in 1877, forming Upper Crystal Springs Reservoir. The old earthen dam became a causeway between Upper and Lower Crystal Springs Reservoirs when the latter was formed by Herman Schussler's concrete Crystal Springs Dam, which dammed up San Mateo Creek in 1888 to form the lower reservoir.
This tributary, Laguna Creek, flows northwards from Woodside with its source on Edgewood County Park and Natural Preserve, and historically supplied Laguna Grande before joining San Mateo Creek near Crystal Springs Canyon, where San Mateo Creek turned east to flow through the canyon. Laguna Grande was submerged when an earth structure (this was the first Crystal Springs Dam) was constructed in 1877, forming Upper Crystal Springs Reservoir. The old earth structure became a passage between Upper and Lower Crystal Springs Reservoirs when the latter was created by Herman Schussler's concrete Crystal Springs Dam, which blocked San Mateo Creek in 1888 to form the lower reservoir.