Dispersion—Mississippi River Below Baton Rouge, La.

Measurements of longitudinal dispersion and lateral and vertical mixing were made in the Mississippi River at a flow of 795,000 cfs (22,511 m³/s). The results show that the longitudinal dispersion coefficient for the 179-mile (287.8-km) reach from Baton Rouge to Point a la Hache, La., was approx 7,500 sq ft/sec (697 m²/s) or about 900 U*R, in which U* is the shear velocity and R is the hydraulic radius. Vertical mixing was accomplished in about 50 miles (80.4 km). A numerical model based on a particular solution of the convection equation was used to aid in data collection. The model provides an accurate simulation of the dispersion process over the entire length of the study reach.