Landsat image courtesy of USGS
Lake Champlain resides in the Eastern Great Lakes Lowland ecoregion on the borders of Canada, New York, and Vermont, USA. Due to geographic positioning the lake has a complex socioecological system with several noteworthy international agreements related to trade, water quality, and ecosystem management. More than 500,000 people reside in the watershed that covers more than 21,326 km2 of mixed forests, agriculture and urban, rural, and suburban transition zones. Approximately 200,000 people depend on Lake Champlain for drinking water with more than 100 systems drawing water for consumption. There are 54 public beaches and hundreds of private homes and recreational beaches. The lake has a large fishing and recreation community with the lake economy projected at more than $4 billion annually. The lake has a volume of 25.8 km3 with a surface area of 1127 km2 that stretches 193 km north-to-south and 19 km east-to-west with average depths of 19 m and a maximum depth of 122 m. More than 70 significant islands dot the lake including many that host seasonal camps. Portions of Lake Champlain can stratify in warmer seasons with an epilimnion extending down to around 10 meters in the main lake basin. The region has mostly humid continental climate with warm summers and cold winters.
Water Quality Overview
DEC and DH 2014 sample locations with bays of interest noted
Lake Champlain has bays undergoing chronic Cyanobacterial Harmful Algal Blooms that pose a potential public health threat. Lake Champlain currently has a tiered alert system for cyanobacteria monitoring led by the Vermont Department of Health (DH) (samples represented as circles in figure to the right). The assessment protocol is a hierarchical framework that increases in scrutiny as reports, sampling, screening, and toxin testing criteria are met. This monitoring program ties in with the Champlain long-term monitoring program led by the Vermont Department of Environmental Conservation (DEC) that began in 1992. Shoreline and within lake samples are systemically collected every two weeks at the DEC stations (green triangles in figure to the right) along with numerous local reports of ‘visual conditions’ from volunteers and the public. If a scum, highly discolored water, foul odor, or potential CHAB indicator are reported or an in situ sample shows indications of CHAB the tiered system is triggered. Once triggered, toxin and phytoplankton samples are obtained and tested for the presence of potential toxin producing cyanobacteria.
CyanoMap has been assessing water quality in Lake Champlain to link with remote sensing images collected from satellite platforms such as Landsat 8 OLI, Rapid Eye, MERIS, and Proba CHRIS. CyanoMap recently visited St. Albans and Malletts Bay in the fall of 2014, during which time St. Albans Bay was undergoing an algal bloom (the pictures to the right were during sampling).
Models were applied to map chlorophyll-a and phycocyanin concentrations. The outcomes showed spatial patterns across the lake with problematic bays. We are combining this higher spatial resolution maps with multitemporal MERIS and Landsat imagery to gauge trends and drivers. The below figure shows a Rapid Eye image and the resulting chlorophyll-a concentration map. The application shows how CyanoMap is being used to support a public health alert system.