The Red River at Fargo Water-Quality (RRatFGO QW) Model, which used the Enhanced Stream Water Quality Model (QUAL2E) computer program, was calibrated and verified for icefree conditions. The purpose of this study was to verify the model for ice-cover conditions using the same Red River of the North study reach that was used for ice-free conditions. The study reach begins about 0.1 mile downstream of the 12th Avenue North bridge in Fargo, North Dakota, and extends 30.8 miles downstream to a site 0.8 mile upstream of the confluence of the Buffalo River and the Red River of the North. The study reach receives treated wastewater outflow from municipal wastewater-treatment plants at Fargo, North Dakota, and Moorhead, Minnesota, and inflow from the Sheyenne River. For simulations conducted for ice-cover conditions, the RRatFGO QW Model will be referred to as the Red River at Fargo Ice-Cover Water-Quality (RRatFGOIC QW) Model.

Streamflow measurements were made at 10 sites during February 21-24, 1995, and water-quality samples were collected and field properties were measured at 12 sites during February 23-24, 1995. Properties and constituents analyzed for include specific conductance, water temperature, dissolved oxygen, 5-day carbonaceous biochemical oxygen demand, total nitrite (reported as nitrogen), total nitrite plus nitrate (reported as nitrogen), total ammonia (reported as nitrogen), total organic nitrogen (reported as nitrogen), total phosphorus (reported as phosphorus), chlorophyll a, and algal biomass.

The RRatFGOIC QW Model simulated streamflow, specific conductance, total organic nitrogen, total ammonia, total nitrite, total nitrite plus nitrate, 5-day carbonaceous biochemical oxygen demand, and dissolved oxygen. The model was considered verified for ice-cover conditions for all of the values or concentrations simulated except for the total organic nitrogen concentrations. Based on the results of this study, the QUAL2E Model computer program that was calibrated for ice-free conditions is capable of simulating water quality for both ice-free and ice-cover conditions.