In early July, an 80-year-old concrete chute east of Golden — normally dry — held water flowing several inches deep for more than a week.

The wet, water-slicked concrete was a rare sight for hikers and bikers on North Table Mountain.

The chute, on the east side of the popular recreation area, is part of the Ralston-Clear Creek Canal that was built by Denver Water in 1937. Water flowed through the canal from June 30 through July 8.

The canal is used occasionally by Denver Water to deliver water from Ralston Reservoir into Clear Creek, which flows into the South Platte River near Commerce City.

While normally dry, the canal plays an important part as a piece of the infrastructure Denver Water uses to do “water exchanges.” Denver Water last used the canal in 2016.

What are water exchanges?

Colorado’s water laws allow water exchanges, which give water managers flexibility in where and how they convey water to downstream users. In an exchange, a manager delivers water to a downstream user from a different source than the user would normally get it from. This allows the water manager to store or divert the same amount of water at a point further upstream.

In this particular case, Denver Water used the canal to deliver water from Ralston Reservoir to Clear Creek, where it could flow into the South Platte River and to a downstream user who called for it. That allowed Denver Water to hold on to the same amount of water in Chatfield Reservoir for use when the utility needs it.

Such water management methods have been common in the industry for decades. The exchanges give water managers more flexibility in their operations while ensuring everyone who has rights to a certain amount of water gets their fair share.

“Denver Water’s early engineers and planners had the foresight to build this canal back in the 1930s because they realized they would need to make water exchanges in the future,” said Nathan Elder, manager of water supply at Denver Water.

“We’re fortunate that they built the canal, because while we don’t use it often, it helps us maximize our water supply when we need to, such as now when we’re experiencing hot and dry conditions on the South Platte River.”

Canals in Colorado

The Ralston-Clear Creek Canal is one of many man-made streams around the metro area that offer a glimpse into Colorado’s water history.

Most of these canals were built in the late 1800s and early 1900s by Colorado’s early settlers as a way of moving water from the mountains to communities and farms. The well-known, 71-mile High Line Canal was completed in 1883.

While many canals were originally simple ditches dug into the earth, many are now lined with concrete or run through underground pipes.

Denver Water’s operating system includes 85 canals and ditches located on both sides of the Continental Divide. Each one plays an important role in how the utility manages its water supply.