House lawmakers heard testimony Monday about an evolving outlook for assessing the water quality of Pennsylvania streams.

A key finding of a new state report is that the percentage of streams with impaired water quality has increased but so has the number of streams assessed.

The topic before the Environmental and Natural Resource Protection Committee was the draft 2026 Integrated Water Quality Assessment.

The assessment by the Department of Environmental Protection shows that more than one-third — 37% — of rivers and streams have impaired water quality compared to 34% in 2024.

DEP added more than 10,000 miles of streams to the new assessment compared to the 2024 assessment, however.

“As a result of the addition of many new miles of assessed streams, DEP added 852 miles of impaired streams to its list, which demonstrates both that we are more accurately characterizing waterways that were not previously included in our reporting, but also that we still have work to do,” said Jill Whitcomb, a deputy state Department of Environmental Protection secretary.

A draft assessment report released last November is open for public comment before it’s submitted to the federal Environmental Protection Agency in April.

The assessment is done every two years.

The main contributors for impaired water quality are agricultural runoff, abandoned coal mine drainage and water runoff from storm sewers in urban areas, the report said.

The focus on restoring water quality in Pennsylvania streams dates back six decades with enactment of a landmark clean streams act to address the ravages of coal mining.

DEP recently expanded its network of 178 water monitoring stations, including stations at Marietta and Conowingo, measuring levels of nitrogen, phosphorus, and sediment in the Susquehanna River, the freshwater source for the Chesapeake Bay.

Water assessment data is key to making decisions about state permits for activities and spending priorities, said Whitcomb.

Asked about funding needs by Committee Majority Chair Greg Vitali, D-Delaware, Whitcomb said it’s important to support the state Environmental Stewardship Fund.

Lawmakers should consider the impact of federal aid cuts related to the Chesapeake Bay cleanup program taking effect in 2027, she added.

Dr. John Jackson, analyst at the Stroud Water Research Center, suggested a need for more and better remediation projects to improve stream water quality.

“The Stroud Center’s approach is to address the whole farm — from fields and pastures to barnyards and even roads,” he said, referring to agricultural runoff.

York County Commissioner Julie Wheeler emphasized the importance of collecting water quality data from real-time sources rather than computer models.

She said state computer models had indicated York County was the second highest contributor of nitrogen and other harmful nutrients to the Susquehanna River.

The county’s water quality monitoring program launched in 2020 shows a better local picture, Wheeler said.