view of full reservoir in 2011 north, dam , spillway in background
the large reservoir, known san gabriel reservoir no. 1, 3 miles (4.8 km) long when full. 525-acre (212 ha) reservoir stores 44,183 acre·ft (54,499,000 m) of water when full, creating 1 of southern california s largest instream reservoirs. 17% less original capacity of 53,344 acre·ft (65,799,000 m) when dam first built, because sedimentation has reduced water volume. interest in sediment removal began in 1980s, after several major wildfires in san gabriel mountains , subsequent flooding caused millions of cubic yards of sediment wash reservoir. reservoir dewatered in 2004 allow sediment removal, work delayed after heavy rains during winter of 2004–2005 refilled reservoir.
disposal of removed sediment has been contentious issue. 2005 sediment removal project stored 6,100,000 cubic yards (4,700,000 m) of sediment in nearby canyon, prohibited due environmental , safety issues. option have been truck sediment local beaches replenishment, has been banned california coastal commission. currently, of sediment sold building material or ends landfill, these options highly limited.
flood control releases coordinated in conjunction other mountain dams, morris , cogswell; , santa fe , whittier narrows dams on lower san gabriel river.
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