This page, Water Quality Monitoring, is part of
This page, Water Quality Monitoring, is offered by

Guide Water Quality Monitoring

MassDEP works to protect our watersheds through a statewide monitoring program. This guide describes how the program works.

Table of Contents

Water-body Monitoring

Physical/Chemical Monitoring: Rivers

Historically, river surveys were typically performed during low-flow, dry-weather conditions which generally represented the worst-case scenario with respect to the assessment of impacts on receiving water quality from point discharges. Today, increased attention is given to the identification and control of nonpoint pollution, and survey methods are changing to reflect this shift in emphasis. For example, wet-weather sampling may provide the most reliable information pertaining to nonpoint pollutant loadings from stormwater runoff and, when compared with dry-weather survey data, may further distinguish the effects of point and nonpoint pollution sources. Surveys are conducted every five years to update old information, and to examine the effectiveness of remedial actions such as treatment facility improvements, or implementation of Best Management Practices (BMPs) for controlling nonpoint sources of pollution.

River surveys are sometimes supplemented by wastewater discharge sampling which serves to document pollutant loading from point sources to the river at the time of the survey, and to assess compliance with NPDES discharge permit limits. In addition, stream discharge measurements may be made to supplement data from USGS stream gages. Discharge measurements provide data for the calculation of pollutant mass loadings, as well as for assessing the impacts on stream biota of low-flow conditions resulting from drought and/or water withdrawals.

Lake Monitoring

MassDEP's Lake Water Quality Monitoring Program was formally initiated in 1974 and was significantly expanded in its scope during most of the 1980s. Historically, limnological sampling was conducted to: a) determine baseline lake conditions, b) monitor post-implementation projects, and c) respond to public concerns about lake problems. The focus of monitoring has changed over time and lake monitoring has been incorporated into the Watershed Approach. Lake monitoring is now conducted in the context of a review of issues within each basin. While overall lake monitoring is less than at the peak of the program, the monitoring conducted is targeted in the highest priority areas.

Lake sampling by DWM is now primarily limited to biological surveys of the macrophyton communities and "in-situ" measurements using metered probes. Baseline surveys by MassDEP are occasionally scheduled under special request or to provide data for TMDL development. A baseline survey is generally conducted in one day and consists of bathymetric mapping of the lake; physical, chemical and biological sampling of the open water areas, tributary stream(s), and outlet; and a quantitative and qualitative mapping of the aquatic macrophyton community in the lake. The primary purpose of this survey is to estimate lake trophic status and identify any point and nonpoint sources of pollution. The lake is sampled during the summer months when productivity is high.

Less intensive "synoptic" surveys have two primary goals. First, they provide information necessary to make a minimum assessment of lake quality. Second, they are used to document the spread of several non-native and potentially nuisance aquatic plant species that are known to be present in Massachusetts.

Coastal Monitoring

While MassDEP has performed some coastal monitoring in the past, this is not a major component of the monitoring program at this time. However, other Federal and State agencies, as well as local entities, do maintain coastal monitoring programs. For example, DMF performs monitoring to support shellfish resource management decisions, and to contribute to their periodic "Monograph Series" of marine resource assessments. In addition, the Massachusetts Water Resources Authority (MWRA) performs extensive monitoring to support outfall siting and Combined Sewer Overflow (CSO) management decisions, as well as to demonstrate the effectiveness of ongoing pollution control efforts. Finally, targeted research has been conducted through the National Estuaries Program to support the development and implementation of Comprehensive Conservation and Management Plans (CCMP). These include the Massachusetts Bays Program and the Buzzards Bay Program.

In 1996, the Massachusetts Office of Coastal Zone Management (MCZM) initiated a Marine Monitoring and Research Program (MMRP). Much of MCZM's initial emphasis has been placed on gaining information necessary to implement BMPs for the improvement of the ecosystem health of coastal embayments.

Additional Resources for Water-body Monitoring


In-stream biomonitoring is an integral component of the watershed-based water quality management program. Its importance is underscored in the Clean Water Act that stresses the need to restore the biological integrity of the nation's waters and achieve a water quality which provides for the protection and propagation of aquatic life. DWM biologists perform habitat assessments and conduct biological sampling to determine aquatic life use-support status, the fish consumption use, and to supplement other water quality monitoring and management programs.

Assessment of Aquatic Community Health

DWM assesses the condition of resident macroinvertebrate, fish and algal populations in streams to provide a direct measure of the ecological response to cumulative effects of pollutant loadings and habitat degradation. Physico-chemical water data can provide a "snapshot" of conditions prevailing at the time of sampling; however, due to their temporal variability, solutes must be measured with some degree of replication in order to draw conclusions with respect to the overall quality of the water. Furthermore, surrogate chemical analytes are less reliable than the more direct biological assessment of instream "health". For example, whereas satisfactory dissolved oxygen values may provide the means for predicting that a given stream is supporting aquatic life, a survey of the organisms that spend all or a portion of their life-cycles in the water furnishes direct evidence that this use is or is not supported. Thus, the analysis of aquatic community structure and function indicates the general condition of the aquatic ecosystem which, in turn, is dependent upon such factors as the quality of the habitat, water quality and flow regime.

Rapid bioassessment protocols (RBPs), based on those developed by EPA, are used to monitor the health of benthic macroinvertebrate communities. These methods were developed to minimize laboratory time requirements for taxonomic identification and enumeration of benthos. Kick-net samples are collected at sites for upstream/downstream comparisons, comparisons against a regional or surrogate reference, or for long-term trend monitoring. Two different levels of analysis are employed, RBP II or RBP III, depending on the objectives to be served.

Based on scoring of several metrics, three categories of impairment are discerned by the RBP II (nonimpaired, moderately impaired, and severely impaired), while the RBP III distinguishes between four (nonimpaired, slightly impaired, moderately impaired, severely impaired). Benthic macroinvertebrate RBPs are conducted at up to 75 sampling sites per year.

The analysis of the overall structure and function of the finfish community as a measure of biological integrity is also a component of the DWM water quality monitoring program. Fish bioassessment data quality and comparability are assured through the use of qualified fisheries professionals and the application of consistent methods. The DWM utilizes a standardized method based on the EPA Rapid Bioassessment Protocol V (RBP V) to improve data comparability among wade-able sampling sites throughout the state.

The fish collection procedures employ a multihabitat approach that allows for sampling of habitats in relative proportion to their local availability. A representative 100-meter stream reach is selected and delineated such that primary physical habitat characteristics of the stream are included (i.e., riffle, run, and pool habitats). Electrofishing has generally proven to be the most comprehensive and effective single method for collecting stream fishes, and is therefore the preferred method for obtaining a representative sample of the fish community at each sampling site. Fish (except young-of-the-year) collected within the study reach are identified to species (or subspecies), counted, and examined for external anomalies, (i.e., deformities, eroded fins, lesions, and tumors). Aquatic life use-support status is derived from a knowledge of the environmental requirements (e.g., water temperature and clarity, dissolved oxygen content, etc.) and relative tolerance to water pollution of the fish species collected. This information may also be used to corroborate findings of other community analyses or water quality testing.

Algae represent a third community that may be assessed as part of DWM biomonitoring efforts. The analysis of the attached algae or periphyton community in shallow streams, or the phytoplankton in deeper rivers and lakes employs an indicator species approach whereby inferences on water quality conditions are drawn from an understanding of the environmental preferences and tolerances of the species present. Algal indicators of the presence of elevated metals concentrations, nutrient enrichment, or other pollutants are noted. Because the algal community typically exhibits dramatic temporal shifts in species composition throughout a single growing season, results from a single sampling event are generally not indicative of historical conditions. For this reason the information gained from the algal community assessment is more useful as a supplement to the assessments of other communities that serve to integrate conditions over a longer time period. In some instances, where information pertaining to primary production is required, algal biomass analysis or chlorophyll determinations may be performed. Results of these analyses are used to evaluate the trophic status of lakes, ponds, and impoundments. Similar information from riverine and coastal waters is used to identify those waterbodies subjected to excessive nutrient enrichment.

Bioaccumulation Assessment

In addition to the community analyses described above, DWM also collects some aquatic organisms to be assayed for the presence of toxic contaminants that may be sequestered in their tissues. The goal of this monitoring element is primarily to provide data for the assessment of the risk to human consumers associated with the consumption of freshwater finfish. In the past fish collection efforts were generally restricted to waterbodies where wastewater discharge data or previous water quality studies indicated potential toxic contamination problems. More recently, concerns about mercury contamination from both local and far-field sources have led to a broader survey of waterbodies throughout the Commonwealth. In both cases, nonetheless, the analyses have been restricted to edible fish fillets. This "Toxics-in-Fish" monitoring program is a cooperative effort of the MADEP, the Department of Fisheries, Wildlife, and Environmental Law Enforcement (DFWELE), and the Department of Public Health (DPH). Uniform protocols, designed to assure accuracy and prevent cross-contamination of samples, are followed for fish collection, processing and shipping. Fish are typically obtained with electroshocking gear or gill nets. Lengths and weights are measured, and fish are visually examined for tumors, lesions, or other indications of disease. Data are provided to the DPH which is the agency responsible for performing the risk assessments and issuing public health advisories.

The use of tissue bioassays to trace the fate and transport of toxic contaminants in the aquatic environment has been explored on a limited basis, as time and resources permit. Caddisfly and crayfish bioassays have been used to identify possible sources of PCB's in selected watersheds. However, the effects of potentially toxic chemicals on the organisms that accumulate them are often not well understood, rendering tissue contaminant data of limited value for inferring aquatic life use support.

Data Management

The Watershed Planning Program’s (WPP) data management team works to ensure that WPP’s monitoring data are of known and documented quality, are valid for intended uses, and are available to staff and the public in a timely manner. WPP’s monitoring data are currently managed in several separate warehouses, and efforts are underway to combine all WPP monitoring data into one database system. This new system will also facilitate data flows to EPA’s WQX database and the Water Quality Portal.

In order to avoid decision errors and provide data users with sufficient information related to data quality, WPP employs a rigorous system of data review checks and validation procedures. The extent to which data are determined to be useful is an on-going in-house evaluation based on cumulative confidence (and uncertainty) in the data, data conclusiveness and results of QC and data analyses. Data for each project are evaluated with regard to both programmatic and project-specific objectives. If certain data do not meet these Data Quality Objectives (DQO’s), data may be censored or qualified. Standard data symbols are used to denote specific problems or issues for final datum. These are applied to both qualified and censored data to provide data users with additional information related to data quality.

Only WPP-collected physico-chemical and biological data are formally managed in WPP databases. Data collected by outside groups and submitted to MassDEP are considered external or secondary data, which are reviewed for usability by WPP separately from internal data validation and management activities.

Additional Resources for Data Management