GREAT SAND DUNES NATIONAL PARK AND PRESERVE — A favorite destination for many San Luis Valley residents and tourists this Memorial Day weekend will be Medano Creek.

Although mountain snowpack in many parts of Colorado is above average, the watershed in the Sangre de Cristo Mountains that constitutes Medano Creek is about 80% of average leaving the creek with less water than banner years.

The park service is forecasting the creek will reach peak flow in the next week and advises that due to below-average snowpack and flow, waves in the pulsing water, floating will be unlikely.

Medano Creek is one of the few places in the world where the phenomenon of surge flow 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. In spring and early summer, these elements combine to make the waves.  
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.

According to the National Park Service:

Current Conditions as of May 24:

• Medano Creek is at the Dunes Parking Area with a wide but shallow flow of water. It flows in braided streams with a total width of about 60-90 feet wide, and 1-4 inches deep.
• Throughout the season, flow is normally highest at dawn, and lowest at dusk.
• Snowpack is 80% of average although heavy rain may temporarily boost flow.
• Check weather forecasts for environmental conditions at the creek.

Because of the creek's popularity, late May and early June weekends can be crowded, with long lines of traffic, overflowing parking lots, a crowded beach, and full campgrounds.
June 2023 Forecast
June brings warmer temperatures for water play and generally pleasant conditions during the first week of June. Late May and early June are the best opportunities to experience surge flow.

When the creek becomes much lower around the second week of June, mosquitoes emerge. Move away from vegetation to the far side of the creek to avoid the worst of the mosquitoes. They do not like open sand and prefer to be near shady bushes and trees. By late June, the water level will be fairly low, only 1 or 2 inches or may even be drying up.
July 2023 Forecast
In July, unless there are significant ongoing rains, the creek will be retreating toward the mountains and will be dried up at the main visitor area near the Dunes Parking Lot. It may continue to gently flow at less than an inch deep along the eastern edge of the dune field, near Castle Creek Picnic Area which is accessible by high clearance 4WD vehicle on the Medano Pass Primitive Road. Visitors without 4WD may also access the creek in late summer by hiking approximately 3 miles up the creek bed from the Dunes Parking Lot, or approximately 0.7 miles from the Point of No Return parking area. Mosquitoes are typically still present if there is low, warm water around the dunes in the first half of July but begin to disappear as the water retreats farther back toward the mountains. July is the warmest month at the park, with average highs in the low 80s.