Capitol Lake algae, weeds in bloom as Lakefair kicks off

By John Dodge | The Olympian • Published July 16, 2008

• Comments (0)

OLYMPIA – When Capital Lakefair festivalgoers head for the shores of Capitol Lake today, they'll be greeted by carnival barkers, music, the mixed aromas of cooking food - and large colonies of pond weed coated with algae in the lake's north basin.

The rooted native aquatic weeds covered with mats of green algae encompass sizeable stretches of the north basin next to Heritage Park, home to many of the Lakefair activities.

The lake weeds and algae are common summer occurrences in the lake, but they have grown visible a week earlier than normal this summer and in greater abundance in the north basin, said Nathaniel Jones, a senior facilities manager for the state Department of General Administration.

"This is the earliest we've seen them. Normally, they're more common in the lake's middle basin," Jones said.

River flows

Theories abound on the unusual north basin weed growth.

It could be tied to more concentrated amounts of nutrients in the water because of lower Deschutes River flows this year, Jones said.

Nutrients act as fertilizers for the aquatic plants and algae.

Here's another possibility: The native plants could be experiencing a boost in abundance and density because of the removal of Eurasian water milfoil, an invasive plant that was thick in the lake four years ago, Thurston County natural resources director Mark Swartout said.

"The one thing about lake weeds, it's amazing how much they can change from year to year," he said.

In addition, the lake has filled with 1.7 million cubic yards of sediment since the Deschutes River was dammed to form the lake in 1951, reducing lake volume by 60 percent, according to a 2006 United States Geological Survey study.

A shallower lake allows summer water temperatures to rise, which also stimulates the growth of algae and aquatic plants.

The lake weeds and algae wreaked havoc on Capital Lakefair Regatta hydroplane races last weekend, with some racers choosing not to enter the water, race officials said.

No other water-related activities are scheduled for Lakefair this year.

John Dodge covers the environment and energy for The Olympian. He can be reached at 360-754-5444 or jdodge@theolympian.com.