UNIVERSITY PARK, Pa. — Pennsylvania’s two largest river basins — the Susquehanna and the Ohio — are not just irrigation and drinking-water sources for millions of people downstream. They also have become fountains of information channeling streams of water-quality data to researchers worldwide.

Regional challenge

Remote sensors dot these waterways to collect and transmit observations through several networks to regional monitoring outposts, partially in response to the increased intensity of Marcellus shale gas exploration.

Additional sensors are being deployed throughout river systems statewide to widen the networks and deepen the data pool in anticipation of increased water use and the potential for widespread contamination due to gas-extraction activities.

“As the Marcellus industry relates to a footprint in the basin, there is going to be use of a significant amount of water, plus additives and return water that could potentially contain a whole host of contaminants that can affect water quality,” said Andrew Gavin, a hydrologist with the Susquehanna River Basin Commission (SRBC).

“This is a challenge that permeates the environmental field,” added Jeanne VanBriesen, a professor of civil engineering at Carnegie Mellon University.

VanBriesen is also the director of the Center for Water Quality in Urban Environmental Systems and performs research in conjunction with the River Alert Information Network, an early warning detection system on major rivers in southwestern Pennsylvania.

The river basins

The Susquehanna River Basin covers about half the land area of Pennsylvania and more than 70 percent of this basin is underlain by the Marcellus Shale, according to the Pennsylvania Department of Environmental Protection.

The Ohio River Basin covers slightly less land area in Pennsylvania, but virtually all of it lies above the Marcellus Shale formation.

Marcellus Shale also underlies about 36 percent of the Delaware River Basin to the east.

Early warning

The SRBC plans to have more than 30 water-quality sensors in place by the end of June, operating in regions where drilling in the Marcellus shale is most active, according to Gavin.

He said the SRBC has operated an early-warning system at drinking-water intakes since 2003 along the main stem of the Susquehanna River between Danville, Pa., and Maryland, and that the larger monitoring network for natural-gas application evolved from that.

What they record. He said the newer sensors are typically being installed in smaller headwater streams, which are more sensitive to contaminants.

The remote sensors, which can cost up to $20,000 per unit, report data on water temperature, acidity and turbidity, which is a measure of the amount of light that can pass through water to plant and animal life beneath the surface.

The sensors also measure levels of dissolved oxygen, an essential element for aquatic life, and conductance, which indicates the amount of dissolved solids in the water.

Gavin noted that to cover the $800,000 price tag for the sensor network, the SRBC invested $250,000 of commission funds, and then received a donation from East Resources Natural Gas Co. for $750,000 to complete the work.

The sensors collect and record data every five minutes and send a summary of that data to the SRBC office every hour.

Watching closely

Gavin said they set thresholds for each parameter they monitor, and if a value exceeds that threshold, the system sends notification to several staff members’ cell phones.

“It’s nice to get an e-mail 24-7 when a water quality parameter goes out,” Gavin said.

If the system does send out an alarm, Gavin said the standard operating procedure is to first verify whether it is an equipment malfunction, and if the alarm is real, a staff member goes to the alarm site and performs some simple measurements onsite.

He said if there is a change in water-quality conditions, his office notifies the Department of Environmental Protection.

River watch. The River Alert Information Network (RAIN) operates an online river-monitoring system to help protect public health and drinking water across southwestern Pennsylvania. The network is a set of 25 to 30 monitoring outposts for drinking-water providers in the region.

An estimated 1.7 million Pennsylvania residents rely on the Allegheny, Monongahela, Youghiogheny and Ohio rivers as their sources of drinking water.

In conjunction with RAIN, VanBriesen said she is looking at other water parameters that can’t be monitored by real-time sensors.

‘Legacy of contamination.’ Her group gathers samples from 10 sites along the Monongahela — six at drinking-water intakes and four at remote sites, including one at Dunkard Creek, the Monongahela headwater that was the site of a major aquatic kill last year, due to a bloom of invasive algae possibly related to a spike in total dissolved solids.

VanBriesen said that waters in southwestern Pennsylvania always have been higher in total dissolved solids, and that there are “many legacies of contamination” in the region.

Abandoned mines, mine discharges and high TDS levels, particularly in the fall months during low-flow conditions, were all drivers for the Pennsylvania DEP to put the observation network in place, she said.

Stressed streams?

She added that Marcellus activity is a main focus for monitoring because local rivers and creeks don’t have many “assimilative” qualities.

“They can’t take much more,” she said. “Even if water is appropriately treated, if it’s going to be discharged or diluted in local waterways, that is a concern.”

Bromide concern. One of VanBriesen’s greatest concerns is whether the Marcellus shale has higher levels of bromide, because elevated levels could lead to what are known as “brominated disinfection byproducts.”

Marcellus formations contain small amounts of ancient sea salt and possible traces of bromide. If source water contains bromide, which is a naturally occurring, nonreactive ion, and that water gets treated with chlorine, it produces bromine, which is a problem.

Bromine is a much stronger disinfectant than chlorine, typically used in hot tubs because it is more stable at high temperatures, but brominated disinfection byproducts are a serious problem in drinking water.

Problems can arise when chlorine reacts with other organic carbons to produce chlorinated disinfection byproducts that are linked to cancer or reproductive problems.