Water-quality indicators in the Delaware River basin are improving and some fish are making a comeback but runoff from paved areas is increasing, invasive species are on the rise, and the salt-water line is creeping upstream from the ocean toward drinking-water intakes in New Jersey and Philadelphia, the Delaware River Basin Commission said Thursday.
In its, its first for six years, the interstate regulator painted a cautiously upbeat picture of the environmental health of the area that stretches from upstate New York to the mouth of the Delaware Bay.
Most of the report’s 31 indicators received a “good” or “very good” rating, said Steve Tambini, executive director of the agency that oversees water quality and supply for the basin, which encompasses parts of New Jersey, New York, Pennsylvania and Delaware.
Among positive indicators was an increase in dissolved oxygen levels, which allow more fish species to breed, thanks to tough DRBC limits on waste-water discharges that had created “dead zones” in some parts of the river until the mid-20th century. The higher oxygen levels have allowed the recovery of fish such as shad.
Concentrations of nitrogen, phosphorous and other “nutrients” typically used in farm fertilizer are declining in the Delaware estuary, the report said, earning that indicator a “very good” rating.
But the report was less sanguine about the outlook for salinity, saying that rising sea levels from a warming planet are pushing more salt water into the river’s tidal section where authorities for Philadelphia and several South Jersey counties have drinking-water intakes.
“With more salt water entering the bay and estuary, the range of the salt front will be pushed upstream,” the report said. “Older modeling studies support the theory that sea level rise will push the salt front further upstream.”
Sea-levels — which are predicted to rise by up to five feet in Delaware Bay by 2100 — “may require new management measures” and reservoir storage to protect the intakes, the report said.
Other aspects of climate change such as higher temperatures and more rain appear to be increasing in the basin, and forecasts for bigger and more frequent storms may require new plans to deal with floods, it said.
Climate change is also creating more opportunities for invasive species of plants, fish, invertebrates and reptiles to enter the river’s ecosystem. Giving that indicator one of the few ratings of “fair and declining,” the report said that higher temperatures and changes to precipitation patterns are likely to allow more invasives to thrive outside of their native ranges, putting more pressure on native species.
It predicted that insect infestations will become more severe and that warmer rivers, lakes and oceans will support more adaptable non-native fish species such as carp and catfish.
“Impervious cover is a good indicator of urbanization and consequently stream health in the Delaware River Basin,” it said, giving that indicator a “good but declining” rating.
Still, the report was more optimistic about the basin’s population of osprey, a fish-eating hawk that is making a strong comeback after being decimated, like many other raptors, by the pesticide DDT in the 20th century. In one example of the bird’s recovery, the number of nestlings in the state of Delaware rose to 434 in 2014 from 135 in 2003, the report said.
Maya van Rossum of the environmental group Delaware Riverkeeper Network said the report contains valuable information but is short on forward-looking solutions for improving the river’s health.
Although the improvement in dissolved oxygen levels has allowed the DRBC to declare the river meets a technical standard that its condition is consistent with its legally designated use, the report does not examine whether that designation is consistent with a better level of environmental health, van Rossum wrote.
“It fails to recognize that the legal designation is itself wanting and fails to provide critical oxygen level protections for fish species like the endangered Atlantic Sturgeon to pro-create and restore their populations,” she said.
“There certainly have been improvements, but much more needs to be done and reports like this should be a strong road map for increasing, proactive and needed protection that would allow us to ensure the highest water quality for supporting basic uses like swimming in all reaches of the river,” van Rossum added.