DEP's outline of an "intensive" effort to study the Susquehanna River is welcome news. The agency announced last week that it will continue its joint work with the state Fish and Boat Commission, the Susquehanna River Basin Commission (SRBC) and the U.S. Geological Survey.

Last May, the Fish and Boat Commission asked DEP to designate the main branch of the Susquehanna River from Sunbury 100 miles south to Holtwood Dam impaired so additional scientific studies could be undertaken to determine the cause of a major decline in smallmouth bass. Before DEP can make that designation, however, the source or sources of the problem must first be known, according to SRBC.

The Fish and Boat Commission since 2005 has been tracking disease prevalence within the smallmouth bass fishery in the river basin. The issue is potentially related to a host of possible "stressors" to the fish community that includes a rise in water temperatures, bacterial or viral infections and "pollutant loadings."

All four agencies already mentioned, plus others, have been studying the smallmouth problems since 2005, but SRBC said data to date has been inconclusive.

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Much focus has been on the west branch of the river, which joins the main branch at Sunbury. The west branch already has "biological conditions" that are concerning, according to SRBC's State of the Susquehanna 2013 Report. It shows that 19 percent of the west branch sub-basin is already considered "severely impaired" and another 27 percent "moderately impaired." In addition, 30 percent of the basin is labeled "slightly impaired," leaving just 24 percent in "nonimpaired" status.

The middle Susquehanna sub-basin, which includes the main branch and Northumberland County, has 4 percent severely impaired, 22 percent moderately impaired and 40 percent slightly impaired. Thirty-four percent is unimpaired.

The west branch has by far the highest percentages of both "severely" and "moderately" impaired status of any of the river's six sub-basins, with the middle basin the next worst.

Impairment can involve many factors: stormwater runoff; sediment and nutrient runoff; acid mine drainage and problems stemming from "low flow." SRBC doesn't list it, but some say Marcellus shale fracking is also suspect, although problems with the river existed long before the natural gas drilling boom began across the northern tier.

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Beyond the recreational and tourism concerns of a threatened fish population, there is much more at stake for those who call the Susquehanna River Valley home.

The river basin provides drinking water for about 4.1 million residents in New York, Pennsylvania and Maryland, and more than 15 million gallons per day are diverted out of the basin to supply public drinking water to another 2 million people. With that, DEP's promised effort to identify the sources of the river's threats is critical, and represents one of the most important environmental concerns facing Pennsylvania.