Microbial pollutants are increasing as a problem in the watershed of the Susquehanna River, but other measures of river health have shown improvement over the past two years, according to latest "State of the Susquehanna" report released this week.
The river is a source of drinking water for about 100,000 people in northeastern Maryland including Havre de Grace and other parts of Harford County and the Cecil County communities of Perryville and Port Deposit.
"Based on analyses of the [Susquehanna River Basin Commission's] nutrient and sediment monitoring data, the health of the Susquehanna River Basin overall is improving. The mainstem of the Susquehanna River meets or exceeds its designated uses along most of its 444 miles," Paul Swartz, executive director of the Susquehanna River Basin Commission, wrote in an overview of the report. The commission is a multi-state compact authorized by the federal government to oversee use and management of the river and its tributaries.
Compiled by the staff of the river basin commission, the report also notes that "The percentage of the basin's assessed stream miles impaired for microbial pollutants doubled between the 2010 and 2012 assessment periods."
Such pollutants, the report notes, result in water treatment plants having to take treatment precautions to make sure water in public distribution systems is safe for drinking.
The report says that in 2010, an estimated 8 percent of the waterways in the river basin were designated as being impaired by microbial pollutants that affect recreational water use or drinking water. The percentage of affected waterways increased to 17 percent during the 2012 survey period.
The report says the basin's overall risk level for potential drinking water microbial contamination in streams shifted in the direction of slightly more being classified as high risk. Microbial contamination consists primarily of bacterial threats. Water treatment plants all treat for bacterial and microbial contamination before water is sent to homes and businesses.
The risk categories, and the percentage of waterways in river basin categorized as such, are as follows:
• High risk waterways increased from 0.5 percent to 0.7 percent;
• Moderate to high risk waterways decreased from 5.9 to 5.1 percent;
• Moderate risk waterways increased from 11 to 13.5 percent;
• Low to moderate risk waterways increased from 40.2 percent to 40.3 percent; and
• Low risk waterways decreased from 42.4 percent to 40.4 percent.
The whole of the river's mainstem from the Pennsylvania state line to the Chesapeake Bay at Havre de Grace is shown in the report as being classified as in the moderate to high category for microbial drinking water risks.