Daily sediment discharges are available for the gaging station Green River above Beaver Creek for water years 1982-90 ( fig. 32 ). Suspended-sediment samples were not collected until October 22, 1980, and the concentration record was not complete enough for daily computations until water year 1982. Sediment concentrations greater than 10,000 mg/L were measured only in water year 1981, and the annual sediment discharge may well have been greater than in subsequent years.
Experimental studies of the tephra-deposited surface were performed at a test plot near Schultz Creek within the Green River basin (Leavesley and others, 1989). Rainfall-simulation measurements in 1980 and 1981 indicated that infiltration rates in the Green River basin were decreased by an order of magnitude from that assumed for the pre-eruption surface. The low infiltration capacity of the tephra deposit resulted in high rates of surface runoff. Erosion rates from the test plot were greater in 1980 than 1981, and a similar trend may have typified erosion in other affected parts of the Green River basin.
