Criteria development for large rivers is underway in some states despite the historical focus on flowing and wadeable waters. The Montana Department of Environmental Quality (DEQ) focused on developing site-specific nutrient criteria for two stretches of the Lower Yellowstone River using the water quality model QUAL2K and AT2K, a companion model that predicts benthic algae growth (Flynn et al. 2014). The DEQ conducted extensive river surveys over the summer of 2007 for calibration of the model and collaborated with the U. S. Geological Survey on river monitoring information from the summers of 2008 and 2009 (Flynn et al. 2014). The researchers modeled river conditions under various additional nutrient scenarios and observed relationships between nutrient additions and physical water quality parameters, such as DO and pH. They found that pH was the most sensitive parameter to increased nutrients (Suplee et al. 2014). While they do not propose new criteria for any nonnutrient parameters, they comment on the impact of nutrients on other water quality parameters (Suplee et al. 2014).
Results and recommendations from this case study were compared with EPA ecoregion recommendations, criteria ranges in existing literature, and nutrient criteria for other Montana rivers (Flynn et al. 2014). The DEQ consequently uses information from this case study using QUAL2K and AT2K to develop site-specific nutrient criteria for the two stretches of the Lower Yellowstone River. The researchers comment on the substantial benefits to using water quality models for creating criteria (Suplee et al. 2014).
Reference:
Flynn, K.F., M.W. Suplee, S.C. Chapra, and H. Tao. 2014. Model-based nitrogen and phosphorus (nutrient) criteria for large temperate rivers: 1. Model development and application. Journal of the American Water Resources Association 51(2):421–446.
Suplee, M.W., K.F. Flynn, and S.C. Chapra. 2014. Model-based nitrogen and phosphorus (nutrient) criteria for large temperate rivers: 2. Criteria derivation. Journal of the American Water Resources Association 51(2):447–470.