Effective modelling of a major inland oil spill on the Ohio River

A model of a large (2700 m3) inland oil spill on the Monongahela/Ohio River System, U.S.A. on 2 January 1988 is developed to estimate the fate and transport time of the oil for 600 km downstream. The emphasis is on developing an effective modelling procedure that balances accuracy with simplicity, is user friendly, and is easily applicable to future spills. Model calibration with oil concentration data suggests that loss of oil due to sedimentation was important. After calibration, the model estimates that 1400 m3 or 52% of the spilled oil ended up in the sediments, most of it in the first few reservoir pools along the river. Both the model and field data agree on similar peak concentrations of oil of between 1.0 and 2.5 ppm (by volume) in the river pools between 130 and 240 km downstream of the spill. The model was further validated by comparing the output with the actual time of travel of the oil spill. Other simulations include the use of resuspension of oil during high flow conditions and an investigation of the role of storms on the time of travel of the oil spill. Model results suggest that the location of the most significant ecological impact was not at the spill site but was between 130 and 240 km further downstream of the greater exposure time there.