A Coupled Modelling and Observing System to Assess Water Quality in the Lake George, New York Watershed

Lake George is a glacial, oligotrophic water body of unusually high clarity in upstate New York. It has experienced ecological changes recently with the influx of invasive species, increasing levels of salt from road de-icing agents as well as nutrient loading from storm water runoff, and the accompanying deterioration of water quality.

To study these changes, we developed a system to observe and model the atmospheric, hydrological, hydrodynamic and ecological aspects of the lake and the surrounding region. This capability is a testbed for addressing related issues in lake watersheds, estuaries and similar ecosystems. It includes real-time access to over 500 sensors that support adaptive sampling driven by forecasted conditions from the models. These data are used for model verification, and to improve model initial conditions via data assimilation. To enable data sharing and software reuse, community data models have been adopted, which also drive geometric modelling to enable fixed and interactive visualizations.

The modelling starts with numerical weather prediction to 333m horizontal resolution for forcing lake circulation and runoff models. Two models address hydrological forcing of the lake. One supports fully dynamic routing with flow driven by both precipitation and snow melt, including over 400 stream networks and 78 outlets with a total length of over 1000 km. The model has been extended for the transport of dissolved salt. To properly inform the hydrological model, an off-line land-surface model established the base flow.

For lake circulation, two hydrodynamic models have been implemented. One uses structured meshes at 50m horizontal resolution, extended to address chlorine ion transport as an indicator of water quality given the tendency of sodium to bind with soil en route to the lake. The other utilizes an unstructured mesh with variable resolution from 10m to 50m. It forces a simple ecological model, which considers nutrients, phytoplankton, zooplankton, small and large detritus, and oxygen to evaluate relative growth of phyto- and zoo-plankton.

We will present an overview of the models and the observing system along with the results to date, including the model coupling and computing infrastructure required for operations. In addition, we will outline recommendations for future work.