The word 'polluted' conjures images of visible garbage, a chemical film on the water surface, malodorous stench, and impaired ability to sustain aquatic life. By that standard Middle Spring is not polluted. While it is not hard to find visible trash in Middle Spring stream and the water is less than pristine, Middle Spring is a pretty country stream, with relatively clean water and abundant aquatic life.
However, any stream that has a human population along its banks is going to experience adverse impacts. Unless the community takes exceptional measures to limit and remedy their impact, the stream will have some pollution in an absolute sense, and Middle Spring is not immune. It has been affected by human settlement and continues to be threatened by "siltation from agricultural runoff", "industrial pollution", and disturbance by commercial and residential development.1 Portions of the stream are officially listed as "impaired", due primarily to agricultural runoff the human settlement in close proximity to the stream.2 and There have also been concerns about whether the Shippensburg Wastewater Treatment Plant has an adverse impact on the water quality of the stream.
Many of us who live near the stream, fish or wade in the stream, or further down the watershed, are curious to know just what the quality of water is in Middle Spring stream and its tributaries. How clean or dirty is the water?
Water testing is the way to answer that question. Tests for water quality can be classified into six types: visual, physical, chemical, biological, hydrological, and other kinds. Visual monitoring looks at tangible trash, siltation, physical disturbances to the ecosystem, and identifies potential sources of adverse impacts. Tests for physical properties measure changes in the temperature, clarity, and conductivity of water. Chemical tests measure the acidity (pH) of the water, dissolved oxygen, as well as nitrogen (e.g. nitrates) and orthophosphates, which come from agricultural runoff, detergents, and other sources, and can destroy aquatic ecosystems. Biological indicators include analysis of macroinvertebrates and stream vegetation. Hydrology is concerned with water level and flow. Other kinds of water quality monitoring include tests for bacteria, sewage treatment discharge reports, and tests for microscopic metal or petrochemical contamination. A variety of water quality tests for Middle Spring stream are conducted by a variety of organizations, though their efforts have seldom been coordinated.
Testing for bacteria, metal contamination, or petrochemicals generally requires sending water samples to a laboratory. Pennsylvania Deparment of Environmental Protection (PA DEP) does bacteria testing of some streams in conjunction with local watershed associations, but MSWA does not do that at this time and is not aware of any group regularly doing these kinds of tests for Middle Spring stream.
The best set of indicators for the overall long-term health and water quality of the stream are probably the biological tests. Shippensburg University Biology Department faculty, their classes, and individual student researchers do biological analyses, mainly focused on macroinvertebrates, once or twice a year on Middle Spring stream and occasionally also on Burd Run and Branch Creek. Their data are available, and show a stream that supports these life forms and is generally health.Shippensburg High School biology classes also monitor the biological impact at various sites along the Branch Creek portion of the stream that runs through downtown Shippensburg.
Short-term fluctuations in water quality of the stream are best measured by tests of the chemical and physical properties of the stream. Both the University Biology Department and the Cumberland County and Franklin County Conservation Districts do some chemical and physical testing of water quality, to provide baseline data, but not on a sufficiently regularly schedule to know much about variations in quality or specific sources of potential pollution.
Middle Spring Watershed Association does occasional visual inspections of the main part of the stream. Additionally, from 2008-2012 MSWA volunteers conducted tests of physical and chemical impact on Middle Spring stream at two sites, one above and one some way downstream of the sewage treatment facility. Data from that testing is available here. This was useful to establish baseline data for the stream and to assess the impact of that facility, but the effort was labor intensive and MSWA was taking only one measurement per month.
To answer the question of how clean or dirty the water is, not just overall, but on a day-to-day basis that allows us to track the effects of intense precipitation events, and on a multi-point basis that helps identify particular sources of pollution, what would be needed is water monitoring at a set of point along the stream on at least a daily basis. It is our hope to soon be able to provide that, and in a way that the data is publicly available so members of the community can see at a glance how dirty or clean the water is on any given day, and have a much better appreciation for things that are adversely impacting the stream.
1 A Natural Areas Inventory of Cumberland County, Pennsylvania -- Update, 2005. Prepared by The Pennsylvania Science Office, The Nature Conservancy, Middletown, Pennsylvania.
2 Middle Spring Creek, Gum Run & Mains Run: Watershed Implementation Plan. December 2009. Prepared by RETTEW Associates, Inc. Lancaster, PA for Cumberland County Conservation District.