The Port of Seattle has started adding water to Des Moines Creek this summer, one year ahead of schedule.

Augmenting water flows into Des Moines and Walker creeks was required by environmental permits for construction of the third runway at Sea-Tac International Airport. The Port operates the airport.

The added stream flow helps fish and other aquatic life in the creeks.

Summer 2008 is the deadline for implementing the project, but the Port was able to begin adding water to Des Moines Creek this summer, according to Bob Duffner, airport water resources manager.

Duffner said a similar augmentation for Walker Creek will begin next summer east of the runway near State Route 509 and South 176th Street.

The Port is also collecting stormwater running off the airport's paved surfaces in detention ponds to prevent flooding of the creeks.

An analysis during the permitting process showed the increased in concrete surfaces could limit the natural infiltration of rainwater into the ground and creeks.

But Duffner noted that it usually takes a full winter of rainfall to bring the level of ground water up to the level needed to maintain creek flows during the drier summer season.

The Port began adding water to Des Moines Creek on July 24 and will continue to pump about 36 gallons per minute until Oct. 1. That will add 10 to 20 percent more water to the creek during the dry months, according to Duffner.

Because heavy summer rainfall will not seriously affect the water levels, the Port will pump a steady amount of water into the creek.

The water is supplied from a groundwater well on the Tyee Valley Golf Course. The Port has donated a portion of the well water rights to the state for this use.

The Port hired Taylor Associates to conduct testing on the project. Taylor supplies test results to the Port, which in turn reports the figures to state regulators.

July 24 may seem late in the summer to begin the augmentation, but Duffner said the Port studied the 50-year history of dry seasons in the area. The study determined that July 24 through Oct. 1 is the best period to offset lack of rainfall.