Prediction of water quality and its application in a hypereutrophic polymictic lake 

Dr. Alicia Cortes
UC Davis

Water quality in lentic ecosystems is threaded by a combined effect of eutrophication and climate change. One of the most common expressions of these changes is the proliferation of harmful cyanobacteria blooms (HCBs) that reduce aquatic biodiversity, yielding increased water treatment costs, and threatening living organism's health through bloom-produced cyanotoxins. Due to the cascade effect, different water quality parameters can indicate and help us predict the HCBs thread. Dissolved oxygen (DO) is essential for maintaining healthy aquatic ecosystems, but both eutrophication and climate change drive DO depletion which normally yields increasing HCBs. Phosphorus (P) has been historically viewed as the limiting nutrient for primary production in freshwater lakes, and increasing P loads in the aquatic systems have a direct impact on HCBs. All these problems are occurring in Clear Lake, CA, a large, multi-basin, polymictic lake with a long history of environmental problems. Clear Lake is prone to episodic hypoxia, hypereutrophic, contaminated with mercury, affected by wildfires, and prone to intense HCBs. The lake has been the site of intensive limnological monitoring for the last 5 years, coupled with the development of a three-dimensional, time-varying hydrodynamic and water quality model. The goal of the model development is to provide an understanding of the factors driving the lake’s degradation and to examine a range of remediation strategies to be implemented in the coming years. In this presentation, I will describe our monitoring and modeling program in Clear Lake and present the predictive tools we are developing, which have been used to test one remediation strategy in Clear Lake named Hypolimnetic Oxygenation System (direct addition of pure oxygen to the bottom of the lake).