Water Quality: Pollutant Monitoring

Resize font A- A A+
OEQ map of sampling stations

There are several different classes of pollutants monitored by OEQ, including solids, nutrients, metals, bacteria, organic matter and others. Additionally, certain physical characteristics are monitored at all sites, including stream temperature, pH, conductivity and dissolved oxygen.  These physical parameters are also continuously monitored at four sampling stations at the locations indicated on the above map.  A general description of each of these parameters and OEQ's sampling program is presented below.

Silt / Solids

When it rains, silt and suspended solids wash off fields, construction sites, roadways, parking lots and other areas into nearby streams. As a result of this, fish respiration can become impaired, plant productivity and water depth may be reduced, aquatic organisms and their habitats can be smothered, and aesthetic enjoyment of the water is reduced. Based on Ohio EPA's Water Resource Inventory for the Year 2008, siltation is the leading cause of aquatic life impairment in the State of Ohio.  As part of its monitoring program, Clermont County measures concentrations of total suspended solids (TSS).


Nutrients are a class of pollutants that include various forms of nitrogen and phosphorus, which can be found in fertilizer, sewage, plant material, detergents, and wastewater effluent. Nutrients are necessary for plant growth. In excess levels, nutrients can lead to excessive growth of aquatic plants and algae, which in turn can deplete the stream of dissolved oxygen as they decompose, and block light to deeper waters. Low DO concentrations resulting from excessive nutrient loads can lead to a decrease in animal and plant diversity, and can affect our use of the water for fishing and swimming.

There are several different types of nutrients that can be monitored, including ammonia, nitrate+nitrite (NO3-NO2), total Kjeldahl nitrogen (TKN), total phosphorus and orthophosphate. Clermont County has collected and analyzed samples for each of these at all sampling sites since 1997.


Metals, such as copper and lead, may enter streams from industrial discharges, runoff from city streets, leachate from landfills, and a variety of other sources. These chemicals, which are generally persistent in the environment, can cause death or reproductive failure in fish and wildlife. In addition, they can accumulate in animal and fish tissue, be absorbed in sediments, or find their way into drinking water supplies, posing long-term health risks to humans.  Currently, OEQ does not routinely sample for metals, but can sample for metals if it suspects that there is a potential for metals contamination in a certain stream reach.


Bacterial organisms and other pathogens can enter waterways through a number of routes, including inadequately treated sewage, storm water drains, sanitary sewer overflows, failing on-site wastewater treatment systems (septic tanks), runoff from livestock pens and livestock entering streams, boats that dump sewage and wildlife. Because it is impossible to test water for every type of disease-causing organism, monitoring programs usually measure indicator bacteria such as fecal coliforms and E.coli that suggest the water may be contaminated with untreated sewage and that other, more dangerous, organisms may be present.

In 1997, Clermont County began monitoring fecal coliform concentrations at each of its sampling locations. Starting in 1998, the focus of the monitoring program shifted to E. coli. Each year, E. coli samples are collected at every sample location from May through October, when recreational activity in streams and lakes is the highest. In addition, the Clermont County General Health District monitors bacteria levels at the beaches in Harsha and Stonelick lakes.

Organic Enrichment / Dissolved Oxygen

Organic material may enter waterways in many different forms as sewage, as leaves and grass clippings, or as runoff from livestock feedlots and pastures. When natural bacteria and protozoans in the water break down this organic material, they begin to use up the oxygen dissolved in the water. Many types of fish and bottom-dwelling animals cannot survive when levels of dissolved oxygen drop below 2 to 5 parts per million (mg/l).

At all sampling locations, OEQ directly monitors the instream dissolved oxygen concentrations.  OEQ also has the ability to measure CBOD5, the 5-day carbonaceous biochemical oxygen demand (CBOD5) concentration. This represents a measure of the amount of dissolved oxygen consumed in five days by biological processes breaking down organic matter.

Back to top