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Continuous Instream Monitoring (CIM) Reports

Continuous Instream Monitoring

Streams, rivers, and lakes are dynamic systems that often require monitoring on a frequent basis to better understand the larger picture of water quality. As a result, the Pennsylvania Department of Environmental Protection (DEP) Division of Water Quality Standards uses deployable instream monitors that collect data up to every 15 minutes. DEP commonly configures instream monitors to measure four parameters: water temperature, specific conductance, pH and dissolved oxygen. Monitors can also be configured to measure additional stream properties such as turbidity and water depth. Deployments are usually for one year but may be shortened in order to capture time periods of specific interest. For example, during the summer, dissolved oxygen can become critically low compared to other times of the year. Several deployments have been maintained for multiple years to understand year-to-year differences and observe trends.

Why Measure Continuously?

Continuous data are valuable for a variety of purposes including, but not limited to, characterizing baseline stream conditions, describing seasonal and diel (24-hour period) fluctuations, and documenting potential violations of water quality criteria. Continuous data can also be used in conjunction with other measurements to estimate loading or establish continuous data for parameters that are difficult to collect frequently. Most importantly, the operation of a continuous water quality monitor produces a record that can be processed and reported to the public.

Continuous Data Availability

Sensors that are used to measure water quality require meticulous field observation, cleaning, and calibration procedures. Additionally, the data require correction, grading, and final approval. All data available through WebPortal and included in the reports have completed these quality assurance procedures.

Reports of CIM data are available using the links at the bottom of the page. In addition to the continuous data, these reports often include other data collected during the deployment such as discrete chemistry grab samples and fish and macroinvertebrate community surveys.

To view or download continuous data, use WebPortal at the link below. Instructions on common tasks in WebPortal are also provided.

Go to WebPortal

WebPortal Instructions

Questions and comments can be directed to Mark Hoger at 717-783-7573 or


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