the pool on the Rio Hondo side of the reservoir is below elevation 201.6 ft (61.4 m) NGVD29, releases are made to accommodate the capacity of the spreading grounds downstream along the Rio Hondo. The spreading grounds are operated by the Los Angeles County Department of Public Works to recharge the groundwater basin. Flow reaches the spreading grounds either directly by way of the diversion passage or from a diversion structure in the Rio Hondo downstream of the dam. Both the diversion passage direct from the dam and the diversion structure in the Rio Hondo are operated by the county. When the water conservation pool on the Rio Hondo side of the reservoir is exceeded, the releases to the Rio Hondo are increased to match inflow until either the capacity of the Rio Hondo or the Los Angeles River downstream are reached. If the water conservation pool on either side of the reservoir is exceeded, discharges on the San Gabriel side can be increased to approximately 5000 ft³/s (142 m³/s). The San Gabriel outlet has automatic spillway gates. When the pool in the reservoir exceeds flood control storage these gates will begin to open automatically. The top of the flood control storage pool is at elevation 228.5 ft (69.6 m) NGVD. The capacity of the Rio Hondo downstream from Whittier Narrows Dam is approximately 36,500 ft³/s (1,034 m³/s). The capacity of the Los Angeles River downstream of its confluence with the Rio Hondo is approximately 127,000 ft³/s (3,596 m³/s), and the capacity of the San Gabriel River downstream of the dam is approximately 13,000 ft³/s (371 m³/s). See also List of dams and reservoirs in California Whittier Narrows References External links Dams in Los Angeles County, California Geography of the San Gabriel Valley San Gabriel River (California) Montebello, California United States Army Corps of Engineers dams Los Angeles County Department of Public Works Dams completed in 1957 1957 establishments in California