The CwM team is proud to be working with the City of Wilsonville to help them manage their water rights portfolio. The City of Wilsonville holds multiple groundwater rights and a large surface water right on the Willamette River. From the late 1980s until the early 2000s, the City depended solely on groundwater from the Columbia River Basalt Group (CRBG) aquifer for municipal supply. The growing City’s demand for groundwater resulted in accelerated groundwater level declines. In 2002, the City brought their state-of-the-art water treatment facility online and switched completely to surface water. CwM was lucky to visit this facility in November, which is now being expanded in partnership with the City of Sherwood and the Willamette Water Supply Program.
CwM’s Bob Long visiting the raw water pump room at the Wilsonville Water Treatment Plant
The City’s rapid transition from groundwater dependence to a surface water source affords a unique opportunity to observe groundwater recovery in the Columbia River Basalts. CwM collected data from six CRBG wells in and around Wilsonville spanning 1960 to present. From the 1960s to 1988, when Wilsonville’s current groundwater system was operational, groundwater levels declined at an average rate of 1.00 ft/year. During the period before the transition to surface water, from 1988 to 2002, the groundwater levels dropped at a jaw-dropping rate of 3.59 ft/year. Amazingly, groundwater levels rebounded rapidly once pumping to meet the growing City’s needs was halted. The recovery averaged 1.33 ft/year from 2002 to 2020. As evident in the plot below, representing data from all six study wells (Wash 3561, Clac 9074, Clac 50585, Clac 8184, Clac 8043, and Clac 278), rate of recovery has slowed as levels approach 1960’s levels. Data like these demonstrate the storage volume of the aquifer and the regional rate of groundwater recharge. With this data, a new sustainable use of the CRBG in this area is possible and gives hope for recovery in other groundwater critical areas of the state.
Plot of groundwater level changes over time. Groundwater level for several wells in the Wilsonville area relative to the level in 2002, when pumping at Wilsonville was decreased. There has been a rapid recovery of groundwater level over the last 18 years.
The Wilsonville Water Treatment Plant office