BERKELEY — Signs of California’s prolonged drought are hard to miss at Tilden Regional Park. Trees are stressed and many have been lost; the park is strategizing which lawns to water and Wildcat Creek is dry in many areas, a problem for resident fish and amphibians.

Perhaps most shocking is Jewel Lake in the Tilden Nature Area, now fondly referred to by park staff as Jewel Puddle. The small lake, home to the Sacramento perch, Western pond turtle, visiting kingfisher and great blue heron has been reduced to a narrow channel.

Jewel Lake, a popular park feature, originated as a reservoir known as Wildcat Creek Diversion Dam, finished around 1921, when water reached East Bay cities via its concrete aqueduct, still evident today.

The lake’s present condition has developed over the last several years.

“It got pretty bad last year and we were worried about completely losing it. The main problem right now is lack of water and there’s a lot of sedimentation in there,” said Hal MacLean, East Bay Regional Park District water management supervisor. “We’ve had some landslides and heavy sedimentation that have really filled up Jewel Lake over the past eight years or so.”

Tilden naturalist Trent Pearce said the lake is 80 to 90 percent silted now, making the water level only a couple of feet when full, and creating a situation where any evaporation creates a drastic change in its volume of water.

Left to nature, this would lead to a natural process of the lake turning into a meadow, but that’s not a direction anyone associated with the park wants to see.

Some of the lake’s wildlife residents have been affected more than others. Its population of Sacramento perch, California’s only native sunfish species, has radically declined.

“We were afraid of losing that population, so about one year ago the park’s Fisheries Department removed a large number of the fish out of Jewel Lake and spread them around to different propagators trying to keep this strain alive,” MacLean said. “Now it’s in different ponds in the East Bay and a mobile fish exhibit at Crown Beach (in Alameda).”

The lake’s remaining fish, mostly gambusia (mosquitofish), are concentrated in a smaller area, making them easy prey for park animals.

The lake has tested positive for toxin-producing cyanobacteria, blue-green algae, and signs have been posted warning against bodily contact.

“Algal blooms like that are fairly common in stagnant, hypoxic (oxygen depleted) water conditions,” Pearce said. “Unfortunately Jewel Lake is experiencing that, as it has no fresh water input and that’s also why it’s evaporating.”

Pearce said the lake’s Western pond turtle population remains active, perching on mud that edges the lake and seemingly unaffected by the algal bloom. Unlike aquatic species, the turtles have the ability to travel upland and estivate for the remainder of the summer.

A study determined the main factors in the sedimentation are erosive forces in the stream and flood plain leading to the lake, including in-stream and bank erosion.

A last-ditch water source is nearby Lake Anza, where flashboards across the dam can be removed allowing for an outflow of water down Wildcat Creek. Unfortunately the water is now only about two inches above the flashboards. They’re typically removed in October, but even then it appears only a small amount of water would make it down to Jewel Lake.

“In the short term what we’re working on is to restore the capacity of the existing sediment basins up through and into Jewel Lake to prevent any additional sedimentation of the lake, and at the same time do some restoration of some ponds and basins that would reduce sedimentation,” said Matthew Graul, park district chief of stewardship.

Money is in place for the project and the park district is working on design and acquiring needed permits. If regulatory approval is given it could begin in August 2016.

A larger, long-range project would look at the bigger picture of sedimentation and eliminate the need for major dredging every 20 to 30 years. This would involve restoring Wildcat Creek around Jewel Lake and establishing an engineered channel that would pass most of the sediment that comes through in a normal rainfall year.

“We would end up with a restored creek tail that would go all around the lake and the preferred alternative would then be to have a fish ladder and no longer have the dam be a barrier to fish,” Graul said. “But we would maintain all the historic structures of the dam for interpretation and then maintain the lake feature.”

This still-undesigned project would cost between $2 million to $3 million. The Regional Water Quality Control Board and California Department of Fish and Wildlife support this idea, as it would help restore and enhance the habitat of the entire area, potentially providing fish access to the park all the way from San Pablo Bay.