Castle Rock
Castle Rock, CO water profile — supply sources, drought status, wastewater reuse, and the key water issues facing the city.
castle rock town of
surface water (rivers/reservoirs) · local government · PWSID CO0118010
Below EPA's 15 ppb lead action level at last testing.
Source: EPA Safe Drinking Water Information System (SDWIS) · 2026 Q1
Castle Rock is a small but growing city and the 18th-largest in Colorado, home to roughly 55,591 residents. Castle Rock's drinking water comes largely from the same regional sources that serve Colorado: Colorado River headwaters, South Platte, Arkansas River, and snowpack.
As elsewhere in Colorado, the central challenge is colorado river. As the headwaters of the Colorado River, Colorado faces both upstream obligations and rapid Front Range growth; the state approved direct potable reuse regulations in 2022.
Colorado reuses an estimated 14% of its treated wastewater and maintains developing reuse programs; Castle Rock tracks exceptional drought conditions on the U.S. Drought Monitor scale.
Explore the Colorado profile for statewide context, or dig into the water issues shaping Castle Rock below.
Douglas County water quality
Source: EPA SDWIS · 2026 Q1
At a glance
- Population ~55,591 (18th-largest in Colorado)
- Primary sources: Colorado River headwaters, South Platte, Arkansas River, and snowpack
- Drought: exceptional conditions
- State reuse rate: ~14% of wastewater
Statewide drought history
% of Colorado in severe+ drought (Exceptional (D4) now).
Source: U.S. Drought Monitor
Common questions
Is tap water safe in Castle Rock?
Castle Rock's largest water system, CASTLE ROCK TOWN OF, serves about 106,822 people. EPA records show 0 health-based violation(s) since 2016 and a most-recent 90th-percentile lead level of 2 ppb (EPA action level is 15 ppb). Always check your own provider's annual Consumer Confidence Report.
Where does Castle Rock get its water?
CASTLE ROCK TOWN OF draws primarily from surface water (rivers/reservoirs), part of Colorado's supply from Colorado River headwaters, South Platte, Arkansas River.
Related water issues
Colorado River
The river that supplies 40 million people has lost roughly a fifth of its flow since 2000, forcing a renegotiation of how seven states share the water.
ExploreDrought
Much of the American West is in a multi-decade dry period that researchers describe as the most severe in over a millennium, reshaping how communities plan for water.
ExplorePotable Reuse
Advanced purification turns treated wastewater into water that meets or exceeds drinking-water standards — increasingly essential in water-stressed regions.
ExploreAgricultural Demand
Agriculture accounts for the majority of consumptive water use in the West, making farm efficiency and water markets central to any supply solution.
Explore