Where Our Water Comes From

Pasadena Water & Power (PWP) works hard to manage its water resources and maintain a reliable, safe drinking water supply for its customers. Most of our water is imported from the Colorado River and Northern California through our partnership with Metropolitan Water District (MWD), but a substantial portion of our water is acquired from our local aquifer, the Raymond Basin.

Local Water from The Raymond Basin

Pasadena’s population has always been progressive and engaged in securing and protecting its water supplies. In the late 1890s, private water companies provided unreliable supply to the community. In 1912, to address this issue, the City began purchasing and consolidating water companies and created the Pasadena Water Department that later became PWP. Protecting the quality of its surface water supplies in the 1920s, the utility purchased portions of the Arroyo Seco and Eaton Wash watersheds.

The Raymond Basin, a 40-square-mile natural aquifer underlying Pasadena and neighboring areas, provides approximately one-third of Pasadena’s water supply. The Raymond Basin is managed by the Raymond Basin Management Board and is the first and oldest groundwater adjudication in the State of California. The City of Pasadena is a member of the 10-member board, representing sixteen agencies that have groundwater rights in the Raymond Basin. The basin is divided into three subareas, Monk Hill, Pasadena, and Santa Anita, with PWP pumping water from the Pasadena and Monk Hill subareas.

The Raymond Basin is replenished through a process called recharge, which occurs when water from rain and surface water infiltrates into the ground and percolates down into the underground aquifer. Water is captured for recharge in the Arroyo Seco and Eaton spreading basins. In 2023, to capture surplus regional supplies, PWP partnered with MWD and other Raymond Basin groundwater producers to implement a program that allowed for over 800 million gallons of additional groundwater storage augmentation. PWP actively captured and recharged over 4.7 billion gallons of stormwater at Arroyo Seco and Eaton spreading basins to further increase groundwater supplies. PWP continues to look for opportunities to partner with agencies to maximize capturing water when available. These efforts help bolster water supply reliability, including increased resilience in times of prolonged drought.

 

Imported Water from the Metropolitan Water District of Southern California (MWD)

As the population of Southern California continued to grow in the 1910s and 1920s, the leaders of Pasadena and other communities realized that the local water supplies could not meet the growing demand. In order to keep pace with the growing demand, the Metropolitan Water District of Southern California (MWD) was created by state law in 1928 with the express purpose of building and operating the Colorado River Aqueduct (CRA). Over the next 13 years, MWD, with guidance from the 13 founding cities, raised funds, passed legislation and bonds, created jobs, and constructed the Colorado River Aqueduct. On June 17, 1941, Pasadena became the first member agency to receive water from MWD. To this day, Pasadena receives approximately two-thirds of our water supply from MWD and provides leadership to the organization as a board member.

In addition to owning and operating the Colorado River Aqueduct (CRA), MWD is one of twenty-nine contractors of the California Department of Water Resources’ (DWR’s) State Water Project (SWP). MWD signed a contract with DWR in 1960 to purchase state water, to again support the population boom in Southern California and the growing demand for water. This was the first contract for the purchase of water from the State Water Project and provided the template for future purchases. In 1972, MWD received their first delivery of water from the SWP.

Currently, MWD is the nation’s largest water wholesaler, this regional system includes aqueducts, reservoirs, and treatment plants to provide water from the Colorado River and from the Sacramento-San Joaquin River Delta to 19 million people, served by its 26 member agencies, including PWP, in Southern California.

 

How Water is Delivered to Your Home

PWP’s water system consists of 500 mile of pipelines, wells, storage reservoirs, booster stations, pressure reducing stations, treatment facilities and interconnections with other water agencies all of which is utilized to deliver water safely and reliably to homes and businesses in our community. MWD imported water is treated and enters PWP’s water distribution system through five interconnections.
PWP pumps the groundwater from the Raymond Basin at our facilities, treats it to eliminate microbes or other contaminants, then either diverts it to a reservoir for short-term storage or pumps it directly into underground water mains for distribution to our customers.

In addition to our infrastructure, PWP employs over 100 staff in our Water division. These staff members are responsible for the management of our water system, which includes construction, treatment, water quality, water resource planning and engineering.

PWP Delivers High Quality Water

Part of PWP’s commitment to safe, reliable, clean drinking water, is the operation of our own Water Quality Lab. PWP’s water quality team is state certified and monitors water quality daily. With the help of trained field staff, samples are taken from more than 300 locations and tested for more than 170 elements to ensure safe, high quality water is delivered to our customers. In addition to daily testing, PWP operates two water treatment facilities, the Monk Hill Water Facility and the Wadsworth Treatment Facility.

The Monk Hill Water Facility began service on July 6, 2011. Located in Northwest Pasadena near JPL, the facility is part of an ongoing effort to remove perchlorate and volatile organic compounds (VOCs) from the groundwater near NASA-operated JPL, which was the site of Army rocket testing decades ago. The plant is funded by NASA by the Federal government.

Long-Term Projects Ensuring Continued Reliability & Resilience

PWP is also investing in alternatives methods for boosting local supply, such as recycled water and stormwater capture. The Water System and Resources Plan of 2020 is our long-term strategic plan for a sustainable water supply and for meeting environmental mandates.

PWP is dedicated to the continued enhancement of our infrastructure to maintain a high-level service to our residents and businesses. To learn more about our ongoing infrastructure projects, please visit our Constructions Projects page for the most up to date information.