Some of Boulder County's tap water starts on the other side of the Divide

When you fill a glass in many Boulder County towns, some of that water may have started as snowmelt on the western slope, then traveled under the mountains to reach you.

That is the Colorado-Big Thompson Project. It is a large system, run by the Northern Colorado Water Conservancy District — known today as Northern Water — in partnership with the federal Bureau of Reclamation. It collects water on the western slope and carries it beneath the Continental Divide to cities, towns, and farms across the northern Front Range, a service area that includes parts of Boulder County. Native streamflow off the foothills is not, by itself, enough for everyone here, so imported water helps fill the gap for many communities.

Why this is useful to understand: water in Boulder County is layered. A community may blend local supplies with project water, and the rules, costs, and reliability behind your tap are bigger than any single creek or reservoir you can see from town. It also explains why water is treated as a serious, shared resource in this region rather than something taken for granted.

Every water provider publishes information about where its supply comes from, so the surest way to learn about your own tap is to ask your city or water district. To learn how the project works and how Colorado administers its water, start with Northern Water, the conservancy district that operates the project, and the state’s water agencies.