Simulating Algal Interactions and Eutrophication Dynamics in Development of the Clear Lake Nutrient TMDL, California
Abstract:Clear Lake, the largest natural lake entirely within the borders of California, suffers from significant nutrient enrichment, causing frequent blooms of blue-green algae that impact municipal water supply, agriculture (irrigation and stock watering), recreation (contact and noncontact), warm freshwater habitat, warm spawning, and wildlife habitat (CVRWQCB, 1998). The major external nutrient source is from watershed runoff, while Past studies also suggest that internal loading from benthic release and nitrogen fixation represent significant contributions to the nutrient budget. Wastewater and groundwater contribute, but not significantly, to nutrient loading in Clear Lake. In order to accurately represent the complex chemical and biological interactions exhibited by Clear Lake, and blue-green algae blooms in particular, a detailed hydrodynamic and water quality model was developed based on an enhanced 3-D Environmental Fluid Dynamics Code (EFDC) modeling framework. The boundaries of the EFDC model were forced by a Loading Simulation Program- C++ (LSPC) watershed loading model. Based on this linkage, the hydrodynamic model was able to simulate water balance, water circulation, and temperature distribution in the lake. The receiving water EFDC model was configured to receive loads from LSPC and subsequently represent the limiting effects of nutrients, the interactions between blue-green and other algal species, nutrient fate and transport within the water column, and dissolved oxygen dynamics. In addition to water column processes, sediment diagenesis was also represented and linked to the water column model to account for internal sources and sinks of nutrients and dissolved oxygen. This capability is particularly useful during a TMDL analysis, where loading scenarios should (and in reality, would) have a direct impact on sediment nutrient contributions to the water column. It was observed that the model is able to simulate both the inter-year and seasonal succession of diatom populations, blue-green algae and green algae, and establish significant relationships between algal biomass, nutrients, and dissolved oxygen. This was demonstrated through successful representation of the worst observed blue-green algae bloom on record (summer of 1990) and the recovery that followed. This capability provides a valuable tool to investigate the relative impacts of sources and sinks in the Clear Lake system, and thus conditions that are critical in maintaining the beneficial uses in the waterbody. Once the Clear Lake modeling system was calibrated and validated to observed physical and water quality data, it was utilized to estimate an appropriate nutrient target for Clear Lake. The nutrient criteria for Clear Lake is narrative, providing an opportunity to utilize the calibrated model to estimate an appropriate, site-specific TMDL target for Clear Lake. Based on the analysis of historical water quality and algal bloom records, a TMDL target and subsequent allocations were developed for Clear Lake.
Document Type: Research Article
Publication date: 2007-10-01
More about this publication?
- Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed. A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.
WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
- Subscribe to this Title
- Membership Information
- About WEF Proceedings
- WEFTEC Conference Information
- Learn about the many other WEF member benefits and join today
- Ingenta Connect is not responsible for the content or availability of external websites