Statistical Assessment of DO in Navigation Pool

Regression equations, relating time-of-travel and average pool temperature to the average and minimum pool dissolved oxygen concentrations, are developed for predicting DO in the LaGrange Pool in the Illinois River. Time-of-travel values through the pool are determined by a volume displacement method programmed on a digital computer. Data is presented to demonstrate the effect the detention time in the pool has on the DO. The correlation between DO and biochemical oxygen demand (BOD) is found to be low, which precludes the use of a BOD factor in the prediction equations. An exponential model is found to best represent the relationship between the variables. During low summer flows, time-of-travel is found to have approximately three times more effect on the DO than does the temperature. Using the prediction equations, the effect of the DO of increasing the navigation channel depth is demonstrated. Nitrification is found to be a significant cause of oxygen depletion. A method for establishing a quality control chart for analyzing continuously generated DO data is presented.