The Yuma Desalting Plant (YDP), which includes the Water Quality Improvement Center (WQIC), discharges effluent from desalted water into the Colorado River in Yuma, AZ just upstream of the Northerly International Boundary (NIB) of the United States and Mexico. Point source effluent from YDP discharges as surface flow from the Main Outlet Drain Extension II (MODE II) into the Colorado River. Quarterly samples of ambient water upstream of MODE II, effluent at the MODE II outfall, and from the river 500 m downstream of MODE II were analyzed for boron, copper, pH, and whole effluent toxicity (WET). The United States Geological Survey (USGS) modeled the mixing zone and plume geometry of effluent released from MODE II using the Cornell Mixing Zone Expert System (CORMIX) modeling software. Quarterly sampling was used to validate mixing models (with percent difference between predicted and measured concentrations no greater than 10%) and the validated parameters were used in the prediction of the dilution of boron, copper, and WET concentrations during the critical conditions scenario of 7Q10 flow of the Colorado River and maximum effluent release. This data release includes the input parameters and modeled output reports from all CORMIX simulations.