Poor water quality plagues Inland Bays

Delaware's Inland Bays have gotten better, especially in open waters, over the last five years but a growing population, impacts from climate change and continued stress from runoff pollution continue to impact water quality, according to the 2016 State of the Inland Bays Report released this week.

One of the unexpected surprises in the report is the improvements in Little Assawoman Bay. Nitrogen and phosphorous levels at almost all sampling stations meet water quality standards there, and levels of oxygen in the water met or exceeded the standards everywhere except Dirickson Creek during summer sampling.

The big question for the staff of the Center for the Inland Bays, the nonprofit that produces the report every five years, is what is working in the Little Assawoman that could be applied to Rehoboth and Indian River bays.

"We have definitely seen encouraging progress in some of our environmental indicators such as inputs of nutrients from point sources and water quality improvements in Little Assawoman Bay," said Marianne Walch, the center's science coordinator. "But lack of progress in some areas, such as nonpoint nitrogen inputs and negative trends in others, such as climate change indicators, suggest the bays will have many water quality and habitat challenges ahead."

The report used 35 environmental indicators to assess the ecological conditions in the bays. This work compared 2011 findings to changes over the last five years.

What researchers found is that Rehoboth and Indian River bays are in better shape in the center of each waterway. The likely reason: better water exchange because of the influence of Indian River Inlet. But the tributaries continue to be nutrient-rich and have poor water quality and low oxygen levels.

Local, state and federal officials have intensely studied the Inland Bays for more than 40 years. Over that time, thousands of septic systems have been removed from the drainage basin, state-of-the-art sewer systems have replaced them and farmers have adopted plans to control runoff from their land.

Yet, nutrient pollution from nitrogen and phosphorous continue to be a significant problem in the watershed, and much of it likely comes from runoff from the land and from parking lots, roof tops and other impervious surfaces, according to the report.

These nutrients cause algae growth, cloudy water and large shifts in oxygen levels. These rapid shifts can cause fish kills.

Walsh pointed to significant population growth – the year-round population doubled in the region between 1990 and 2000 – as well as the increase in paved surfaces and significant changes in land use as significant changes in the estuary.

Scientists believe that once impervious surface reaches 10 percent, water quality degrades. In the Inland Bays, the percentage of impervious surface is at 10.4 percent and is much higher in some urbanized areas, she said.

Another major concern is the impact of climate change from more frequent and stronger storms to shoreline erosion and inundation, she said.

In Dewey Beach, municipal officials are already coping with increase flooding along the streets that front Rehoboth Bay.

"We cannot pump and pave our way out of this situation," said Mike Dunmyer, a Dewey Beach commissioner.

"We know that we need to be more resilient (to the impacts of sea level rise),"  said David Small, secretary of the state Department of Natural Resources and Environmental Control.

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Finding new and innovative ways to stabilize shorelines will be a key component as the region copes with climate change, he said.

"We know this area is going to continue to grow," he said.

Small said Sussex County's efforts to replace septic systems with central sewer have played a major role in reducing nitrogen and phosphorous pollution and new stormwater regulations should help reduce both nutrients and sediment entering the bays and the tributaries.

As center officials look toward possible solutions, Executive Director Chris Bason said reaching out to landowners and seeking more grant money could encourage the planting of cover crops to reduce pollution runoff from farms.

About 8,000 acres of farmland in the watershed are planted with winter cover crops, he said. In the Maryland Coastal Bays watershed, thousands more acres are planted with cover crops that uptake excess nitrogen and phosphorous from the land.

"We can do a lot better," he said. "The real area that we need to focus on is agriculture."

Among the issues center scientists would like to explore next are why other estuaries like the Maryland Coastal Bays and the shallow coastal bays in New Jersey can support underwater grasses, but Delaware's do not. There are almost no eelgrass beds in Delaware's Inland Bays, but they used to be common here.

They are also curious why water clarity, even in shallow waters near shore, is so poor during the summer.

And they would like to know what has worked in Little Assawoman Bay to make conditions there significantly better than they were five years ago.

"The State of the Bays reporting provides a time to ask ourselves ... how we are doing in meeting our goals to restore and protect Delaware's Inland Bays," Walch said.

"Here we are five years later," Bason said. "How are the Inland Bays doing? It's not simple. Science never is."

Contact Molly Murray at (302) 463-3334 or mmurray@delawareonline.com. Follow her on Twitter @MollyMurraytnj.