Water Quality Monitoring

Knowing something about the plants and animals that live in, or occasionally visit, your pond can be a source of considerable enjoyment. For most pond owners, the first step in acquiring that knowledge is to get some identification guides (books or internet sites) that include common aquatic species of the region. A sketch of the pond, recording the distribution of plants along the shoreline or submersed beneath the water surface provides an indication of its habitat diversity, and can be useful in detecting changes in vegetation (for example, invasion by alien plant species).Water quality in a pond usually depends strongly on inputs from the watershed of 1) water (which helps to determine water volume and flushing rate), 2) dissolved nutrients (which directly control the growth of algae and aquatic plants), and 3) soil particles (which become pond sediments and also contain growth-promoting nutrients) from the watershed.

We suggest, for those owners with the interest and ability, development of a simple, self-sustained monitoring program to record seasonal and yearly trends in water quality and in the occurrence of particular plant and animal species. Involving older children in data collection, for example, can provide an excellent educational activity during summer or as a school science project. Measurements during the growing season (e.g., May - September) are especially useful, as the combined effects of light, nutrients and warmer temperature on plants and algae are much more evident. Longer-term (year-to-year) measurements by a retiree or other resident near the pond are helpful if carried out consistently as a means of detecting changes in pond water quality. Some ideas for measurements and equipment needed to develop a monitoring program are summarized below.

sechi meter

Secchi disk

               Suggestions for monitoring pond water quality.
Light PenetrationSecchi Disk
Temperature and Dissolved Oxygen Dissolved Oxygen Meter or Test Kit
Water LevelStaff Gage
Spec. ConductanceConductivity Meter

Some equipment can be built at home. For example, a Secchi disk1, fashioned from a metal disk 20 cm (8 inches) in diameter and painted as shown, can be lowered into the pond to determine the extent of light penetration. Consider joining the "Secchi Dip-In" (http://dipin.kent.edu/) to learn more about the importance of light penetration as an indicator of pond water quality. Pond test kits are most easily obtained from local Penn State University Cooperative Extension offices; water chemistry samples are also conveniently analyzed by Penn State. Even limited amounts of water quality information can lead to a much clearer perception of what to do when the pond begins to "act differently", and sometimes the monitoring data can serve as evidence that land use alteration elsewhere in the watershed has negatively impacted pond water quality.

Water quality changes over time, and a regular schedule of sampling is thus preferable. For example, light penetration, temperature and dissolved oxygen all change very predictably with the seasons. Heavy rainfall during the growing season may greatly increase nutrient loading to the pond, causing unusual bursts of algal growth.

New housing construction, if proper erosion controls are not followed, may contribute enough sediment in a short time via surface runoff to substantially impair pond water function. Less obviously, increased housing density may lead directly to pond problems through inputs of nutrients from septic tanks and fertilized lawns. Control by pond owners over watershed influences may be limited, but depends both on good stewardship of the land directly adjacent to the pond and an understanding of the legal responsibilities of other landowners within the watershed.