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Group 2 Delaware River Watershed Initiative


DRWI’s Forest Protections are Moving the Needle on Water Quality

A new report from Open Space Institute (OSI) quantifies the many benefits of the Delaware River Watershed Initiative’s (DRWI) forest protection program on water quality. Protecting Forests for Clean Water: Findings from A 10-year Initiative to Promote Best Practices Across the Land Conservation Field, wraps up findings based on OSI’s DRWI work to protect 21,000 forested acres between 2013 and 2023.

The report’s key findings include:

  • Forests keep water clean. Stream sampling studies found nitrogen levels spiked when forest cover levels fell below 66 percent. When forest cover is maintained at 70 to 90 percent or greater, streams and rivers stay healthier and cleaner, and wildlife thrives.
  • Protecting forests along streams filters pollutants from the surrounding landscape. The land protected by DRWI grantees filters and reduces about 1,680 pounds of total nitrogen annually, with rates increasing if development occurs nearby.
  • Allowing protected land to return to forested conditions results in quantifiable reductions in pollutants. More than 600 acres of the land protected by the fund were returned to forested conditions, which resulted in 4,070 pounds of total nitrogen exported annually from these areas.
  • In largely forested headwaters, loss of forest cover was most strongly correlated with reductions in macroinvertebrates, a key water quality indicator, rather than increases in upstream farmland or development.
  • Across the 21,000 acres protected, land protection resulted in the avoidance of an estimated $57 million in total stormwater capital costs and $6 million in annual maintenance costs for projected development—more than three times the cost of the land protection itself.

“While we know forest protection supports clean water, we need the data that makes that case clear to decision makers,” said Abby Weinberg, OSI’s Senior Director of Research. “Thanks to the creativity of our scientific partners, we were able to develop new approaches and recommendations that allow water utilities, land protection leaders, and agencies to connect the dots between forest protection and clean water, opening the door for greater collaboration and impact across sectors.”

“From the beginning of the Delaware River Watershed Initiative, the William Penn Foundation has looked to OSI’s leadership to translate science into practice. Their assessment shares that work with the broader field,” said Stuart Clarke, Program Director, William Penn Foundation. “Land protection has been under-utilized as a tool for protection of clean water in part because it is challenging to measure and quantify impacts on water quality. This new data will allow communities and agencies to be more strategic in land protection investments for improved water quality.”

“This report contributes to our understanding of the critical role that forests, wetlands, and other natural areas play in protecting and restoring waters to support healthy ecosystems and human communities,” said Dave Arscott, Research Scientist and Executive Director of Stroud Water Research Center.

As the research lead for the modeling components of the study, Arscott also noted, “The research findings and lessons developed with OSI provide a roadmap for how land trusts, states, and other partners can better integrate land protection in clean water programs. In many cases, water quality reflects land use practices. This report provides a means for integrating programs that are focused on either of these precious and limited resources. The project team expects the report will benefit existing and future land conservation programs.”

In addition to providing new data on water quality across the preserved acres, the report offers new methods for assessing how land protection benefits water quality. It also recommends next steps for supporting the integration of land protection with clean water programs.

Learn more and access the report here.

The Delaware River Watershed Initiative is generously funded by the William Penn Foundation.