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Inland Lakes

The Illinois EPA conducts and supports a number of inland lake monitoring program efforts. Collectively, chemical, physical, and/or biological data have been collected from nearly 2,000 lake stations since 1977. Water quality monitoring programs consist of ambient, ambient-core, intensive, and volunteer-based efforts.

Ambient Lake Monitoring Program

Illinois EPA conducts an Ambient Lake Monitoring Program (ALMP) at approximately 50 lakes annually to diagnose lake problems, encourage development of management plans, and to evaluate the effectiveness of programs implemented. ALMP monitoring involves the collection of water quality and sediment samples as well as field observation data including water color, weather, amount of sediment, algae and macrophytes, and other important aspects of the lake. These lakes are monitored five times yearly; once during the spring runoff and turnover period (April or May), three times during the summer (June, July, and August), and once during fall turnover (September or October). A minimum of three lake sites are usually monitored, with water samples collected from one foot below the surface at all sites and two feet above the bottom at the deepest site. Parameters analyzed include suspended solids, nutrients, chlorophyll, dissolved oxygen/temperature (profiles), and other field measurements.

To enhance the Agency's ability to assess lake trends, approximately one-half of the 50 lakes sampled each year are monitored on a three-year cyclic period. A total of 75 significant publicly-owned lakes have been chosen to be included in this core trends monitoring program that began in 1991.

Illinois Clean Lakes Program

To meet the requirements of federal and Illinois Clean Lakes Program (ICLP) regulations and grant agreements, intensive lake-specific monitoring is conducted and consists of Phase I diagnostic/feasibility and Phase II implementation project evaluation monitoring. For ICLP Phase I and II projects, monitoring is generally conducted twice a month from May to September and monthly from October to April for a one-year period. Water quality samples are collected from one foot below the surface, mid-depth (at deeper lakes), and two feet above the bottom at the deepest site. Surface samples (one foot below the surface) are also collected in at least two other lake sites. In addition, major inflows and outflows are monitored (i.e., suspended solids, nutrients, etc.), and nutrient, sediment, and hydrologic budgets are developed. Additional Phase I monitoring and/or mapping activities include: major biological resources (i.e., phytoplankton, fish populations, aquatic vegetation, and sometimes zooplankton and benthos); bathymetric (water depth) maps; sedimentation surveys (conducted on an as-needed basis); fish contaminant monitoring conducted pursuant to the Fish Contaminant Monitoring Program; and surficial and/or core sediment sampling and analyses.

Volunteer Lake Monitoring Program

The Volunteer Lake Monitoring Program (VLMP) has been administered by the Agency since 1981 and relies on citizen volunteers. The VLMP is an educational program for Illinois citizens to learn about lake ecosystems, as well as a cost-effective method of gathering fundamental information about inland lakes.

The VLMP "Basic Program" includes training volunteers to measure water clarity (transparency) using a Secchi disk, an eight-inch diameter weighted metal plate painted black and white in alternate quadrants attached to a calibrated rope. The disk is lowered into the lake, and the depth at which it is no longer visible is noted. This Secchi depth is used to document changes in the transparency of lake water within a given year, and to develop transparency trends over many years. Monitoring is conducted twice a month from April to October, typically at three sites per lake. The basic program also includes monitoring for zebra mussels. The main purpose of this program effort is to determine whether or not zebra mussels are being transported from the state's major rivers to inland lakes.

The VLMP "Expanded Program" includes volunteer collection of water samples from one foot below the surface of the water, in addition to the collection of Secchi transparency and zebra mussel information. Samples are shipped to Agency laboratories for analysis of important water quality parameters including: ammonia, nitrates, total phosphorus, and total and volatile suspended solids. Chlorophyll sampling and analysis is also performed. Water samples are collected at twice the Secchi depth, filtered and sent to Agency laboratories to determine the amount of chlorophyll (the green pigment found in algae and other plant cells) in the water. Chlorophyll data, Secchi transparency information and water quality measurements are used for assessing a lake's condition or trophic status.

Fish Contaminant Monitoring

Fish samples collected at inland lakes are analyzed for 14 chemical contaminants as part of the Fish Contaminant Monitoring Program. Fish samples are collected and analyzed from approximately 25 stations on Illinois' inland lakes on an annual basis.