Modeling total dissolved gas production and transport downstream of spillways: Three‐dimensional development and applications

Abstract

Challenges a resource manager encounters concerning water quality downstream of dam spillways are well documented. The plunging and air‐entraining nature of spillway flows can lead to supersaturated water downstream of the dam. A multi‐dimensional numerical model is developed for predicting total dissolved gas (TDG) production and transport downstream of a hydropower dam spillway. The model is based on the Reynolds averaged Navier‐Stokes equations for flow hydrodynamics and a total dissolved gas model that incorporates the gas production, exchange and transport physics. A three‐dimensional version of the model is calibrated using one set of available field data with a moderate flow discharge. The applicable range of the model is established by applying the calibrated model to different spillway discharges and comparing results with field data. The model is then validated with TDG field data available for Wanapum Dam and applied to two practical engineering problems. The simulations successfully reproduce the convection dominated TDG levels downstream of spillways as well as the variation of TDG concentration across the channel.