Summer Drinking Water Supply

  • Waluga Reservoir
  • Waluga Reservoir

During the spring, winter and fall, rain feeds our rivers (surface water) and refills our aquifers (groundwater) to provide drinking water to our region. In the summer, when there is little rainfall, water supplies are less plentiful.


Despite the weather, we are lucky in our region to have many sources of water and water providers who plan ahead to ensure we have an adequate supply of drinking water any time of the year. Here are some things to know:

  • Water sources, supply, and treatment methods are different throughout the region and the state. Learn more about how our region’s water systems respond to high water demand or drought below. Find out more about regional water supplies and who they serve here.
  • Your local water provider and other state and federal agencies track water supplies closely throughout the year, especially during the summer months. The Oregon Water Resource Department provides a weekly water conditions report which you can sign up to receive via email.
  • The Consortium’s 20+ water providers have worked together for almost 25 years to ensure that the region's water needs can be met in the face of drought or other water shortages. Portland metropolitan area water providers continue to work closely throughout the year to track the region's changing water supplies and are ready to proactively address any issues that may arise.
  • Water providers and their customers take conservation seriously. Despite population growth, per capita water use has steadily declined in the region in large part due to water conservation. Learn more about how you can use water wisely at home and outside.

 

Water systems and how they respond to high water demand or drought

The Bull Run Watershed is primarily a rain-fed system, so there is less water entering the storage reservoirs in the summer when rainfall decreases. The 9.9 billion gallons of stored water supply in the reservoirs typically meets Portland and its wholesalers’ needs through the summer. The Columbia South Shore Well Field can also be used to supplement surface water or replace the Bull Run supply entirely due to turbidity or other issues. The Portland system is resilient to drought and other water shortage events due to its access to two water sources.

The Trask / Tualatin River system is highly managed by its users and regulators to ensure water supplies are sufficient to meet peak summer demand. Barney Reservoir and Hagg Lake allow the Joint Water Commission to store water from the winter for later release in the summer. Some providers also have access to other sources, such as aquifer storage and recovery wells, the Bull Run Watershed, and the Columbia South Shore Well Field.

The Clackamas River is carefully managed to meet all water needs. The community works together to conserve water to ensure there is enough water for people and fish. The river system has no drinking water storage facilities, such as dams, so municipal water providers and other users rely on natural stream flows or “run of river” to meet water needs all times of year, including the summer when stream flows go down. Fortunately, some water in the watershed is stored as snow which melts over time, keeping water cool for fish and providing a gradual release of water into the river. The Clackamas River is also fed by rain and groundwater.

The Willamette River is a reliable year-round water supply. The system is highly managed by a number of dams operated by the US Army Corps of Engineers to ensure water supplies are sufficient to meet peak summer demand flows for drinking water, and agricultural and environmental needs.


To provide additional reliability, the City of Wilsonville's former water supply (a system of eight local wells) is available for use during dry periods or other emergencies. The Tualatin Valley Water District and the Cities of Hillsboro and Beaverton are working on developing the Willamette Water Supply System which will come online in 2026. This new system will enable project partners to manage their various supply sources to respond to drought or other supply interruptions as well as recover more quickly from a large natural disaster.

Groundwater is less vulnerable to short-term water shortages and extreme weather events than surface water sources, but it is still vulnerable to drought. Water providers that rely on groundwater depend on rain, stream flows, and snowmelt to replenish aquifers. Depending on the geology, this recharge can take weeks, years, decades, or longer to occur. Groundwater levels are regularly monitored to track aquifer conditions.


Aquifer Storage and Recovery (ASR) is a resource that some water providers use to supplement their water supply during drier, warmer months when customer’s water demand is high. It involves putting treated drinking water into aquifers when water is plentiful in the winter and then pumping it out in the summer.