Water Bureau: Rain not yet enough

Officials say they will continue to supplement city's water supply with groundwater wells

The recent rains have replenished the city's water supply in the Bull Run watershed, but not enough for the Portland Water Bureau to turn off its supplemental Columbia South Shore groundwater wells.

Bureau officials said they would wait to see if the rains continue for a few more days before switching off the groundwater wells, which have been adding water to the city's supplies since Aug. 15. The extended forecasts calls for both rain and rain-free days during the coming week.

'The news is good. The prudent thing to do is to keep the wells on until we are sure the refill trend is consistent over the next few days,' said bureau spokeswoman Tricia Knoll.

According to Knoll, as of Monday morning, more than 1 and 1/2 inches of rain fell at the Headwaters facility at the dams in the watershed, where the water is disinfected before flowing into the city. Around two and three-quarters inches of rain fell at the North Fork, which is higher in the watershed.

But Knoll says it takes time for all of the rainfall to make it into the reservoirs, and that the rains must continue falling for a few more days before bureau officials can be confident Bull Run can once again provide all the water the city needs.

The groundwater supply is traditionally tapped once more water begins flowing out of the Bull Run reservoirs than flowing into them, a period the bureau called 'drawdown.' Because this summer and fall has been hotter than normal, the period started early and has already lasted longer than usual.

'Portland is fortunate to have a second water supply,' said bureau director David Shaff. 'Few cities do.'

When the temperatures were in the 70s, the city's demand for water was between 100 million and 110 million gallons per day, with the wells providing around 70 million gallons a day. Shaff said the wells could provide even more water - up to 100 million gallons a day - if necessary for up to 90 days.