HEADWATER STREAM ACIDIFICATION IN THE TUSCARORA FORMATION, VALLEY AND RIDGE PROVINCE, PENNSYLVANIA

Pennsylvania has some of the lowest pH rainwater in the United State due to acid deposition resulting from fossil fuel combustion. Within the Valley and Ridge Province, the Tuscarora, Juniata, and Bald Eagle Formations form most of the ridges and host most of the headwater streams. 645 Pennsylvania headwater streams (400 stream km) originate in the Tuscarora (or the equivalent Shawangunk) Formation, a quartz arenite containing a small percentage of other mineral constituents that can buffer acidity.

We sampled 54 locations (in 34 streams) in six counties. All except two of the sampled streams that 1) originate in the Tuscarora or Shawangunk, and 2) have not received water from mapped tributaries originating in other formations have 4 < pH < 6 and are acidified or at high risk of being acidified. Brook trout (Salvelinus fontinalis) cannot survive at pH values lower than 5.5 to 5.0. Extreme headwaters originating in the Juniata and Bald Eagle have low pH, but pH increases to > 6 within short reaches (100’s of meters) of stream origins. Juniata and Bald Eagle streams flowing into Tuscarora streams can add enough alkalinity to allow for pH recovery and for brook trout to thrive. Evidence suggests that limestone gravel roads parallel to streams increase the pH of streams that would otherwise be acidified.

We are developing a geographic information systems (GIS) database for the Pennsylvania Valley and Ridge, based in part upon the Pennsylvania Department of Environmental Protection (DEP) 305b list (“impairments”.) Approximately 15% of Tuscarora streams (approximately 60 stream km) are officially “impaired” due to atmospheric deposition and low pH, on the DEP 305b list.

We hypothesize that 60 to 80% (240 to 320 stream km) of the stream lengths that originate in and flow through the Tuscarora Formation in Pennsylvania without receiving waters from other formations are acidified due to acid deposition and should be re-evaluated to determine if they are currently impaired. Additional chemistry sampling, fish sampling, and mapping will be performed this summer.