TURLOCK -- A series of unfortunate but natural events has left the pond at Donnelly Park full of algae, many of the fish that live there dead, and the neighborhood around it pervaded with a putrid smell.
Dan Madden, the city's municipal services director, explained at a City Council meeting last week what happened: Algae bloom, a natural phenomenon, occurred, filling the pond with thick green algae.
"When that occurs, it limits the transmission of light into the water," he said. "The algae begin to die off, depleting the oxygen in the water."
Higher temperatures exacerbate the situation, as does nitrate from the droppings of hundreds of geese that populate the park year-round, feeding off generous bread and other scrap handouts from visitors.
"A large population of fish has been depleted relatively quickly," Madden said. "The fish float to the surface and begin to decompose."
Decomposing fish, combined with dying algae, make for a strong odor, which the wind blows into neighboring residential areas. The result: a green pond, dead carp and that smell, which has spurred several complaints to the city and to council members.
Thursday, Youbert Esavi was at the park with friends for a regular chess game. He said that in warmer weather, there's often a smell from the water, but in the past few weeks, it's been especially bad.
On the days the smell is particularly intense, "I don't stay," Esavi said. "It's no good for the head."
The answer is simple, but not easy. The pond needs more water. And lower temperatures would help.
The city could add water, but Madden said he's hesitant to do that with the only available option the city's drinking water.
"It's a closed system," Madden said, so there isn't any river or other water source feeding into it.
"We have to balance our resources," he said, "I'm reluctant to push too many gallons of drinking water into Donnelly Lake."
Two months ago, Madden said, the city did release about two feet of water into the pond. For now, the city sends staff to the park to remove the fish and keep the pond as clean as possible. A crew worked in the area Thursday afternoon.
"We've got maintenance crews out there, working every day," Madden said. "But those geese produce a lot of waste, and it's a circle of fish kill."
Bee staff writer Patty Guerra can be reached at firstname.lastname@example.org or (209) 578-2343.