Water supplies article

Risks to Water Supplies in PA’s Susquehanna Basin

In this series of articles on the Susquehanna River Basin, FracTracker has explored the relationship between oil and gas extraction and the overall health of the watershed relative to oil and gas extraction impacts. We began with a basic overview of likely relationships, followed by an analysis of oil and gas violations relative to resources available for monitoring water quality changes. In the most recent article we assessed the corresponding effects of extraction on deforestation and habitat loss. With the rapid expansion of oil and gas drilling over the past decade, many have also formed legitimate concerns about threats to public and private water supplies. In the final article of the series we look closely at this issue, at the complexities of assessing risks to water supplies, while also highlighting recent research shedding new light on the nature of these risks.

Pennsylvania’s Hydrological System

The Susquehanna River is home to more than 3.3 million people who depend on the river and its tributaries for drinking water. The basin also feeds thousands of businesses that require water for their operations, such as manufacturing facilities, farms, golf courses, and more. In some instances, water supplies are fed by groundwater wells, which are in turn fed by underground aquifers of different depths. In other cases, water supplies are drawn from intake points in nearby lakes, rivers, and streams.

Map of PA's groundwater aquifer system.

Figure 1: Map of PA’s groundwater aquifer system.

While many believe underground and surface water systems are somehow discrete, this is far from the case. Groundwater is a major contributor to rivers, lakes, and wetlands – as they are all connected through the hydrological cycle. Some precipitation runs directly into streams. But much of it filters through soil and rock into shallow and deep aquifers. Aquifers then carry water over the course of months, years, and even centuries, into larger water bodies. The most common discharge points are from springs and from low-lying wetlands. The figures above (figure 1) and below (figure 2) illustrate Pennsylvania’s four major aquifer types, compiled by Penn State Extension.

Figure 3: Types of groundwater aquifers in PA.

Figure 2: Types of groundwater aquifers in PA.

Assessing Groundwater Supply Risks

Managing the overall health of the hydrological cycle is of critical importance to the 3.3 million people who live in the Susquehanna River Basin. However, oil and gas extraction poses significant risks to the state’s water sources. As we have detailed in prior articles in this series, accidents and spills can cause chemicals and hydraulic fracturing fluids to run off into nearby watersheds. Growing evidence also suggests that groundwater can be contaminated by migrating hydraulic fracturing fluids.

Figure 4: Number of household and public water supply groundwater wells by state (DCNR).

Figure 3: Number of household and public water supply groundwater wells by state (DCNR).

In one study, conducted by Columbia University in 2016, researchers found elevated levels of dissolved calcium, chlorine, sulfates and iron in lowland drinking wells within one kilometer of a drilling site compared to baseline averages. In lowland wells more than a kilometer away, they found elevated levels of methane, sodium, and manganese. Elevated levels dropped off in wells on higher ground, which suggests the hydraulic fracturing process affects shallow and deep groundwater sources along different timelines.

According to the PA Department of Conservation and Natural Resources (DCNR), Pennsylvania ranks second in the nation for total number of groundwater wells, second for number of private drinking wells, and third for number of public water supplies dependent on groundwater wells (figure 4). However, determining how many groundwater wells may be at risk to oil and gas extraction is complicated for a variety of reasons. First, DCNR acknowledges that only about half (480,000) of the 1 million groundwater wells in the state are documented. Registration of groundwater wells only began in 1955, and detailed information including latitude and longitudinal coordinates only came into being in the 1980s. These records are now maintained in the PA Groundwater Inventory System (PAGWIS). It is worth noting that the PA Department of Environmental Protection (DEP) does not regulate private drinking water wells. They are only required to respond to pollution complaints.

Correlating O&G Wells to Complaints Data

Despite these data gaps, we can still learn a lot from the wells that are documented in PAGWIS. For instance, we compared the location of groundwater wells to oil and gas related complaints and found some interesting correlations. The below map can be used to explore these relationships.

Map of at-risk groundwater wells, public water supplies, and citizen complaints

View Map Fullscreen | How FracTracker Maps Work

The first stage our analysis involved narrowing the PGWIS registered groundwater wells in the Susquehanna Basin to those that are actively used for drinking water, agriculture, and irrigation (66,306 total). We then limited to those within 1 kilometer of an oil and gas well, essentially mirroring the distances used by the Columbia University study. We found 2,551 groundwater wells within this “risk zone” of 1 kilometer.

For our second stage, we utilized research conducted by Public Herald, an investigative reporting team that spent three years reviewing oil and gas related complaints submitted to the DEP from 2004-2016. They found 9,442 total complaints, of which 43% were water related (surface and groundwater), and that the frequency of complaints track with the rise and fall of unconventional oil and gas development (figure 5).

Figure 5: Relationship of complaints to O&G development (Public Herald).

Figure 4: Relationship of complaints to O&G development (Public Herald).

From the Public Herald dataset, we found 1,573 total complaints were in the Susquehanna River Basin, of which 65% were water related complaints — a much higher percentage than the larger dataset’s average. We then compare the location of these complaints to our “risk zone” groundwater wells and found a statistically significant correlation between the number of groundwater wells within 1km of oil and gas activity and higher numbers of complaints by residents. What do these findings tell us?

In short, where we see more groundwater wells in proximity to an oil and gas well, we also see more water related complaints to the DEP.

The below graph illustrates this relationship (figure 6).

Figure 6: Relationship of complaints to at-risk groundwater wells.

Figure 5: Relationship of complaints to at-risk groundwater wells.

Groundwater to Surface Water Risks

DCNR estimates that Pennsylvania’s streams and wetlands get about 2/3 of their flow from groundwater sources. Meanwhile, there are 786 public water suppliers in the Susquehanna River Basin that are fed by different arrangements of groundwater and surface water sources. These suppliers are included in the interactive map for reference.

Assessing risks to public water supply systems is equally complicated to that of groundwater wells. The DEP regulates public water suppliers under the Safe Drinking Water Act, but the general public is not permitted to know the location of actual water sources or intake points due to security risks. This restriction poses a problem for nongovernmental organizations when doing analyses that would benefit from knowing the locations of these source points. Nevertheless, like our breakdown of risk zone groundwater wells, we can still learn a great deal from what we do know of public water supplies.

Figure 6: Wellsboro, PA, public water supply along with O&G wells and water-related citizen complaints in the supply watershed.

Figure 6: Wellsboro, PA, public water supply with O&G wells and citizen complaints in the supply’s watershed.

For instance, the town of Wellsboro, in Tioga County, is home to an estimated 3,300 people. The Wellsboro Municipal Authority supplies water to Wellsboro residents as well as to 1,000 people in surrounding Charleston and Delmar Townships. According to DEP records, groundwater and surface water sources for this system come from Hamilton Lake and tributaries of the Charleston Creek Watershed, much of which is designated as high-quality coldwater fisheries. Nevertheless, there are seven unconventional oil and gas wells in this watershed, one of which is only 400ft from Charleston Creek, just upstream from Hamilton Lake.

The area is also one of the brightest hot-spots for complaints to the DEP in the Public Herald dataset, with 40 water related complaints in Charleston and Delmar townships.

These relationships should be of particular concern to residents who believe their water is protected from extraction industry activities. In addition, while recent research suggests homes values can be negatively affected in neighborhoods dependent on private well water near drilling activity, correlations between potential groundwater and surface water pollution suggest that any changes in home value are more a matter of perceived rather than actual risk—homes on public water supplies should also be considered at risk in communities experiencing extraction.


Returning to the hydrological cycle, we can assume that pollutants from oil and gas extraction, like precipitation, will eventually find their way into larger water bodies, either directly through runoff into watershed tributaries or through groundwater migrations. While this article has primarily focused on the Pennsylvania headwaters of the Susquehanna, home to 570,000 residents, and risks to their water sources, groundwater complaints are not the exclusive problem of residents who are dependent on private drinking water wells. “We all live downstream” as the saying goes, and those who rely on the watershed for their drinking water and other water resource needs throughout the watershed should be concerned by the correlations illustrated in our analysis.

By Kirk Jalbert, Manager of Community based Research & Engagement, FracTracker Alliance

Feature image: Hydrologic cycle graphic by Watershed-Watch.org

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