Rehoboth’s Lake Gerar is healthy, but slowly filling in

According to Envirotech owner Todd Fritchman, Lake Gerar in Rehoboth Beach is a vibrant, healthy, environmentally diverse body of water. It’s also going through aquatic succession, he said, which means that it’s slowly filling in from the bottom.

Fritchman and his company have been maintaining the lake for the past two decades. Lake Gerar serves a number of different functions, said Fritchman during his annual update on the lake at a commissioner workshop Oct. 11. It’s an amenity, a fishery and it’s aesthetically pleasing, he said.

“It’s also a nutrient sink,” he said.

In both prongs of the lake, the bottom is rising, creating a bog and leaving it only a few inches deep in some places, he said.

There are two areas contributing, said Fritchman. First, the properties on the peninsula of land on the western portion of the lake have 100-year-old trees that add a layer of organics every year. What falls off those trees is sinking to the bottom and just sitting there, he said. These are mature, biomassive trees, he said.

Second, the lake has nine stormwater lines draining into it. Every time it rains, said Fritchman, the sediment from disturbed soil zones at all the residential construction sites around town is flushed into the lake.

The Atlantic red cedars in the northwest portion of the lake have been doing well, but grubs have killed some, said Fritchman. 

The city has taken some measures to manage the lake’s water quality over the years, including the installation of diffusers throughout, creation of a riparian buffer and steps to control the goose population. Fritchman said a good balance has been reached in the width of the buffer, but the problem is now vines because they have a competitive advantage. Loads of vines have been removed over the past month, he said.

After two straight summers without a recreational water advisory, the state issued several for Rehoboth Beach this past summer. Commissioner Edward Chrzanowski asked Fritchman if the nutrients in the lake getting flushed after storm events could be playing a part in the recent advisories. Fritchman said yes. 

Discussion on the health of Lake Gerar – specifically, the southwest prong – is expected to continue during the commissioner workshop Monday, Nov. 7.

For years, Fritchman has been recommending the city dredge the southwestern portion of the prong, which has been filling in at a faster rate than the rest of the lake because, he said, winds push the falling biomass and sediment into the prong.