HYDRODYNAMIC MODELING OF THE CARSON RIVER AND LAHONTAN RESERVOIR, NEVADA

The RIVMOD hydrodynamic model was used to route upstream flows through a 115 km section of the Carson River and Lahontan Reservoir, Nevada. RIVMOD results will later be used to predict sediment movement and ult imately to determine mercury transport within the river/reservoir syst em. Significant modifications to the model computer code were necessar y to represent the narrow, steeply sloping rectangular channel and rel atively shallow sloping floodplain of the Carson River and its conflue nce with the Lahontan Reservoir, These changes include expansion of th e continuity and momentum equations to account for rapidly changing ch annel widths along with the characterization of a complex cross-sectio nal shape. This modified version of the RIVMOD model can handle shallo wer side slopes and much more severe flood flow simulations than the o riginal version. A 0.25 km spatial increment was required in the zone of confluence between the river and reservoir. Model predictions show excellent agreement with observed downstream flow and reservoir stage for the entire 1986 water year, which includes one of the most severe flood events of recent record.