Sediment transport, particle sizes, and loads in lower reaches of the Chippewa, Black, and Wisconsin Rivers in Western Wisconsin

Hydraulic and sediment data were collected at three sites on the Chippewa River (near Caryville, at Durand, and near Pepin); at one site near Galesville on the Black River; and at one site at Muscoda on the Wisconsin River during water years 1976-83. This report summarizes an interpretation of those data by providing (1) a description of the relation of suspended sediment, bedload, and total-sediment discharge to water discharge; (2) a description of particle-size characteristics of bed material, bedload, and suspended sediment; and (3) estimates of annual and average annual suspended load, bedload, and total-sediment load for water years 1974-83. Direct measurement with a Helley-Smith bedload sampler and calculations by the modified-Einstein procedure were used to estimate bedload.

Single equations describe the suspended- and totalsediment transport-rate relations for Chippewa River at Durand and main channel at Pepin, and the Black River near Galesville. Two equations were needed to define the transport- rate relations for the Chippewa River near Caryville and Wisconsin River at Muscoda.

Bed material at all sites except Chippewa River near Caryville were of similar particle size and exhibited little variation with time or location in the river cross sections. Median diameter at these sites ranged from 0.35 to 0.84 mm (millimeter). At Chippewa River near Caryville, median diameter ranged from 0.42 to 15 mm. Helley-Smith bedload at Chippewa River at Durand and near Pepin, Black River near Galesville, and Wisconsin River at Muscoda were of similar particle size. About 57 to 65 percent of bedload at all sites except Chippewa River near Caryville was in the 0.4- to 0.6- mm size range. About 50 percent of bedload at Chippewa River near Caryville was in the 0.5- to 1.0-mm size range. Suspended sediment at all sites except Chippewa River near Caryville was in the sand-size range; the average median diameters were between 0.17 and 0.22 mm. At Chippewa River near Caryville, 60 percent (on the average) of suspended sediment was finer than 0.062 mm.

Average annual total-sediment load and the percentage transported as bedload were determined for a 10-year period (water years 1974-83)(October 1,1973-September 30, 1982). These loads and percentages were, respectively, 123,000 tons and 35 percent at Chippewa River near Caryville; 1,073,000 tons and 61 percent at Chippewa River at Durand; 940,000 tons and 44 percent at Chippewa River near Pepin; 277,000 tons and 43 percent at Black River near Galesville; and 558,000 tons and 49 percent at Wisconsin River at Muscoda.