GREAT SAND DUNES NATIONAL PARK AND PRESERVE — Medano Creek in the national park will be a favorite local destination for many San Luis Valley residents and tourists this summer. 

On a recent visit, the creek was running about 20 feet wide and very shallow, at only an inch or two. According to the National Park Service, the peak flow of the creek is about 40 cubic feet per second (cfs) and is at its maximum in late May. On May 9, the flow was very low, at about 7.2 cfs. 

During this visit, the sand dunes' parking lot was full, and many visitors were frolicking in the creek's waters. 

According to the National Park Service, the 2025 flow is only about 50% of the historical average for May. Prior to the recent rain and snowfall, the Medano Creek watershed was estimated to have about 42% of normal snowpack. The park service and the Colorado Department of Natural Resources estimate peak flows this year to be a maximum of 10 cfs. 

The depth and duration of the flow this year are estimated to be less than a third of normal. 

The beginning of June is the best opportunity to experience "surge flow", where waves flow across the sand.  

As we approach summer, it's important to remember that due to the creek's popularity, weekends are extremely crowded, with long traffic lines, overflowing parking lots, a crowded beach, and full campgrounds. To ensure a more enjoyable visit, it's highly recommended to plan your visit on a weekday this time of year, when the crowds are significantly less. This advice will guide you to a more pleasant experience at the park. 

Although mountain snowpack in many parts of Colorado was above average, the watershed in the Sangre de Cristo Mountains that constitutes Medano Creek is less than half of the average; the creek may dry up early in the summer season. 

On May 1, the National Integrated Drought Information System reported that considerable snowmelt occurred throughout Colorado between April 10 and 17, disappointing many water recreationalists.  

Medano Creek is one of the few places in the world where the mesmerizing surge flow phenomenon can be experienced. Surge flow is a stream flowing in rhythmic waves on sand. Three elements are needed to produce the surge: a relatively steep gradient to give the stream a high velocity, a smooth, mobile creek bed, in this case, sand, with little resistance, and sufficient water to create surges. These elements combine in spring and early summer to create the captivating waves, a sight that will surely leave you in awe.  

As water flows across the sand, underwater sand ridges called antidunes form on the creek bed, gathering water. When the water pressure is too great, the dams break, sending down a wave, or surge, about every 20 seconds. 

As the creek becomes much lower around the second week of June, mosquitoes emerge in large numbers. Move away from vegetation, to the far side of the creek to avoid the worst of the mosquitoes: they don't like open sand but prefer to be near shady bushes and trees.