Monitoring and Assessment of Lakes - Data

Much of the lake monitoring in the state is done to assess "trophic state" or the productivity of the water. Our 30 year record includes data on over 1000 of our 5785 lakes, including parameters such as transparency, conductivity, alkalinity, total phosphorus and chlorophyll-a. These, along with extensive data sets from the University of Maine and clarity readings from volunteers, have produced one of the most comprehensive lake data sets in the country. Much of these data are available through the Lakes of Maine website.

DEP regular monitoring includes annual Baseline Sampling Program and special projects of one or more years’ duration. Each year between August 10 and September 10, we visit over 100 lakes and take a number of types of data. The timing coincides with the period when lakes usually show their worst water quality: lowest dissolved oxygen, lowest transparency and highest algae and phosphorus levels. Besides these measures, we sample for conductivity, alkalinity and acid neutralizing capacity (ANC), true and apparent color, and a variety of cations and anions. Over the last 5 years, we have collected biological samples for zooplankton, pytoplankton and sedimented diatoms as part of ongoing bioassessment projects.

We also work with the Volunteer Lake Monitoring Program (VLMP), which has over 400 volunteers working on more than 350 lakes each year, and train a limited number of volunteers each year to do advanced monitoring on their lake, especially if it is associated with a regional or multi-year project, or for Town Comprehensive Planning.

These data allow us to give some recent information to our monitors and the public. It also allows regional and statewide studies into lakes questions ass varied as the relationship between watershed conditions and lake vulnerability to phosphorus loading or the link between lake water quality and economics. Sampling during other times of year is done in response to specific data needs such as setting appropriate water quality goals for watershed management or responding to reports of algae problems by local residents.

Assessment activities include water quality trend detection, data management and quality assurance and analyzing our data record to understand how our lakes work.

Data Management

Information is only useful if it is high quality. Keeping track of over 400,000 pieces of water quality data, plus thousands of other related data points, is a huge task. All this information must be available at a moment’s notice, and as free of errors as we can make it. We have develop a detailed set to Standard Operating Procedures and Quality Assurance Project Plan which guide both data acquisition (monitoring) and handling (data management). Our staff cooperates with the VLMP to do periodic quality assurance and re-training visits with our monitors and error-checks the data we receive from them. As a result, the data we get from our volunteers is as reliable as data received from professionals. Even our staff has consistency checks each year, and we include careful calibration of our lab and field equipment. We duplicate-sample 10% of our field data and scrutinize the laboratory quality assurance information annually to ensure we get high quality data.

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