Out-of-control Weed Growth Choking Pine Lake

By Ryder W. Miller

Though seemingly idyllic, the patches of pleasant looking plants growing on the surface of Pine Lake at Stern Grove are actually unwanted weeds which threaten to cover the surface of the lake, altering the lake's ecology - and that is only one of the lake's problems.

The lake has been overgrown before and efforts are underway to contract for the use of the Aquamog, a machine that removes plants from the surface of the water. The last attempt was not fully successful.

"It is about time to do it again," said Dennis O'Rorke, site supervisor at Stern Grove. "Last time it worked fairly successfully."

In removing the growth, the City's Recreation and Park Department is between a rock and a hard place, said Dan Murphy, former president of the Golden Gate Audubon Society. If they pull the weeds physically they will not be able to remove all the growth and will be taking out some bird nests.

The other alternative uses herbicides. Rec. & Park will probably not get approval to use them, although the effects were negligible the last time herbicides were used.

"Weeds don't include the willows and the bulrushes," reminds a worried Murphy, who pointed out that birds would be better off if they waited to remove the growth in September.

"They don't need to do this during the nesting season," Murphy said.

A new integrated pest management specialist is on the job, but Rec. and Park has not decided what they are going to do yet.

"We have to wait for the ideas people come up with," O'Rorke said.

"Hypothetically it will cover the surface of the lake and wipe out the whole lake," said Murphy.

The water level at the lake is also a big concern. The threat of floating weeds is compounded by the shallowness of the lake, which has made the lake's water a lot warmer than it should be.

Lake Merced is also in a disastrous situation with an average depth about nine feet below its historic levels of 25 to 27 feet. Experts estimate the lake has lost about half its water.

The suspected cause is the over-drawing of the Westside Basin aquifer, which has "stressed" the lake. Pine Lake is connected to the same aquifer as Lake Merced, causing the water levels of the two lakes to drop concurrently.

One proposed solution is to reduce the water take at the aquifer so it can recharge, allowing the water levels of the lakes to increase.

Murphy believes studies are needed at Pine Lake, like the ones that have been done at Mountain Lake Park, to get a full picture of the situation.

He is also concerned about the massive runoff at Pine Lake each day. The surface runoff from the lawn to the east is loaded with dog feces, allowing rain to carry bacteria into the lake.

Ken Sato, principle environmental health inspector for the SF Health Department, said Pine Lake was an ornamental lake which was "not approved for water recreation sports, such as swimming and wading."

Sato said there was going to be an increase in the bacterial count because of runoff - due to birds, animal droppings and the soil.

At this point there is little or no risk from incidental exposure to the water.

The changing conditions at the lake have been noticed by visitors.

"If they clean this lake it would be nice," said Sunset District resident Elizabeth Ulanovsky. "It is a beautiful lake. It is nice to have it here."

In 1868, Pine Lake, then called Laguna Puerca, was much larger; it was once a rowing lake for visitors at the nearby Trocadero Clubhouse.

There is still a lot of wildlife to be found there. The area is awash in the sound of local birds, many of which are attracted by the seeds of the Eucalyptus tree.

Murphy has been conducting a study of birds that can be found around Pine Lake. The list includes the nesting Pied Billed Grebes, Mallards, Red Winged blackbirds and Song Sparrows, which nest in the willows.

"It gets a lot more migrants than anybody dreamed of," Murphy said. "It is better for land birds than water birds. A lot of ducks don't hang out there."

The nearby Eucalyptus forests support a lot of migrants. The trees provide food for many birds, but the oils the trees produce have also changed the soil, which has had an impact on the natural indigenous habitat.

Some of the fish found in the lake include carp and mosquito fish, but the Rec. and Park Department is not sure what is there.

"We really don't know what kind of fish are at Pine Lake," said Randy Zebell a gardener speaking on behalf of The Natural Area Program. "The expectation is that they are non-native."