A 2-year study during 1982-83 was made to document the streamflow gain-and-loss and suspended sediment characteristics of the South Platte River, Fort Morgan Canal, Upper Platte and Beaver Canal, and the Lower Platte and Beaver Canal near Fort Morgan, Colorado, prior to possible construction of the proposed Narrows Reservoir. Six streamflow gain-and-loss investigations, conducted in 1982 along a 25.8 mi reach of the South Platte River, indicate an average downstream gain in discharge of 150 cu ft/sec during the irrigation season. The Fort Morgan Canal and the Lower Platte and Beaver Canal had decreasing discharges in the downstream direction. The Upper Platte and Beaver Canal had a slight increased in discharge at the second measurement site and decreases in the third and fourth measurement sites. Irrigation practices and some loss to the groundwater system account for the general decrease in discharge. Suspended sediment data were collected at the streamflow-gaging station 06758500 South Platte River near Weldona and on the three irrigation canals: Fort Morgan Canal, Upper Platte and Beaver Canal, and Lower Platte and Beaver Canal. The data indicate that relations exist between the suspended sediment concentrations at the South Platte River station and the suspended sediment concentrations at the most upstream measurement site on each canal. Relations between suspended sediment discharge and water discharge were developed at all canal measurement sites. For all the canals, suspended sediment discharge decreased in a downstream direction. Slight increases in suspended sediment occurred at the second measurement site on the Upper Platte and Beaver Canal and at the third measurement site on the Lower Platte and Beaver Canal. Laboratory analyses indicate that 75% of the suspended sediment is silt and clay size (particles finer than 0.062 mm).
