Pennsylvania Watersheds at Risk: Water Supply Decline

Our goal was to determine which PA watersheds will face supply issues in the coming years with a focus on those where fracking activities are further threatening the water supply through both quantity and quality issues. To accomplish this, we conducted a study using the Geographic Information System based assessment tool, Forest to Faucet 2.0 (F2F2). This tool helps land and water management professionals identify watersheds important for protecting drinking water and assess threats like wildfire and yield decline to water supply (Mack et al., 2022).

Water yield decline values were determined using the F2F2 dataset and watersheds with oil and gas related withdrawals and/or fracking wells within them were trimmed for the analysis. Of the 421 watersheds with fracking activities, 60% of those watersheds (250) are within the national percentile top 25% of the projected water yield decline by 2090 (Figure 1), and two of the watersheds are within the national percentile top 1% of the projected water yield decline. These are considered most at risk of water decline within the fracking region in the face of climate change.

The F2F2 dataset also evaluates the relative importance of these watersheds as drinking water sources using an Index of Importance to Surface Drinking Water Model and Drinking Water Protection Model (IMPR). This model takes into account both the quantity of water produced and the population supported by a watershed. Watersheds in the top 25% are those that are more important than 75% of the nation’s watersheds for supplying drinking water.

We found that 75% of watersheds (317) with fracking activities were in the national percentile top 25% of IMPR watersheds. Notably, 29 of these are in the national percentile top 1% of IMPR watersheds (Figure 2).

For this study, we overlapped watersheds of importance to drinking water protection with data of at-risk water supplies. This helped us identify watersheds that are both important for drinking water protection and at risk of declining supply.

A total of 210 watersheds were determined to be important surface drinking water resources with projected yield decline and containing fracking activity. These watersheds and nearby water withdrawal sites used by oil and gas operators can be explored in the interactive map below.

The legend “No,No” means that fracking activity is not present, thus the watersheds were not considered in this study on risks to supply decline. The legend “Yes,No” means that fracking activity is present but the watersheds IMPR and yield decline are not both at risk. The legend “Yes,Yes” means that fracking activity is present and the watersheds are important for drinking water protection and at risk of declining supply.

Each watershed contains information on their area in square kilometers, mean annual yield in gallons, the calculated population served by intakes downstream (by individual watershed), the IMPR percentile value, and the projected water yield decline by 2090 percentile value.

Of the discussed IMPR watersheds expected to face water yield declines, about 85% are within the Ohio River Basin. The five million people served downstream by surface water intakes are at risk of higher concentrations of harmful chemicals in their water and increased water costs.