Estimate of sediment discharges, Santa Ana River at Santa Ana and Santa Maria River at Guadalupe, California

The computed sediment discharge of Santa Ana River at Santa Ana for the water years 1968-71 was 11,700,000 tons (10,600,000 tonnes) of suspended sediment and 5,000,000 tons (4,500,000 tonnes) of coarse sediment. The computed discharge of Santa Maria River at Guadalupe for the water years 1969-71 was 9,500,000 tons (8,600,000 tonnes) of suspended sediment and 6,000,000 tons (5,400,000 tonnes) of coarse sediment. Estimated mean annual coarse-sediment discharge for the 31 water years, 1941-71, is 230,000 tons (209,000 tonnes) in the Santa Ana River and 300,000 tons (272,000 tonnes) in the Santa Maria River. Streamflow in the Santa Maria River was adjusted to represent 1971 conditions. The 31-year mean annual volumes of coarse-sediment discharges are 190,000 cubic yards (140,000 cubic metres) in the Santa Ana River and 250,000 cubic yards (190,000 cubic metres) in the Santa Maria River.

Only during floodflow is any significant quantity of sediment transported. In the Santa Maria River an estimated 99 percent of all coarse sediment was transported in 1 percent (113 days) of the 31-year period.