sand dunes

Spring runoff created above-average water levels of Medano Creek, but the same levels aren't expected this year.

This short National Park Service video reveals the creek's attraction, and explains mysterious "surge flow." Video courtesy National Park Service 

A seasonal phenomenon like no other across Colorado's natural sanctuaries is starting to show.

But it might be a few more weeks before the ultimate "surge flow" at Great Sand Dunes National Park and Preserve, rangers say. That's the term for Medano Creek's rhythmic waves, which in years of intense runoff can swell up to a foot high at the base of the dunes.

That type of surge is not expected this year. Based on snowpack measured in the surrounding mountains, forecasters are calling for "average" conditions. In such years, the park maintains peak flows of 40 cubic feet per second, typically occurring in late May and early June.

Of course, "average" is no way to properly describe the annual beach scene at the Great Sand Dunes.

"Whenever I see it, it's always extraordinary," said Kathy Faz, the park's chief of interpretation and visitor services.

Visitors flock for the aquatic discharge every year, soaking in the sun at this otherwise dry valley as they would at some tropical oasis. If depth allows, kids and adults alike float down the creek with inflatables.

Late May is recommended, or before the second week of June, when the water typically lowers, temperatures rise and mosquitoes emerge. In that time frame, a weekday visit is advised.

The weekends "are extremely crowded," the park website warns, "with long lines of traffic, overflowing parking lots, a crowded beach, and full campgrounds."

With COVID-19 restrictions lifting and cabin fever from last year's shut-down, Faz said the park is anticipating more visits than the record half-million from 2019. That year, droves came for historic flows from above-average snowpack.

For visitors with four-wheel drive vehicles, Faz recommends driving to northern, less-crowded stretches of stream along the park's Sand Pit and Castle Creek areas.