Operation of the Garrison Diversion Unit may have some affect on the hydrology of the James River in North Dakota and South Dakota. The Garrison Diversion Unit Monthly Operations Model was developed to analyze a wide range of streamflow conditions that could occur in the James River Basin. The purpose of this study was to compute monthly streamflows that are required as input to the model.
Historic streamflow data were complied and record extension methods were used, when necessary, to compute monthly streamflow for 1983-91 for 15 gaging stations on the James River in North Dakota and South Dakota. The record extension methods used include Maintenance of Variance Extension Type 1, Ordinary Least Squares, and drainage-area ratio.
In addition to the historic streamflow, synthesized unregulated streamflow was computed for the 15 gaging stations on the James River for 1983-91 by eliminating the effects of Jamestown Reservoir, Pipestem Reservoir, Sand Lake National Wildlife Refuge, consumptive surface-water withdrawals, and wastewater withdrawals. Maintenance of Variance Extension Type 1, Ordinary Least Squares regression, water-balance procedures, and drainage-area ratio method were used to compute the unregulated streamflows.
