Water levels are expected to drop rapidly in the coming weeks to levels only seen three times in the last 30 years. Photo: C. Adams // NPS

MOOSE, Wyo. — Grand Teton National Park announced yesterday, July 20 that the Colter Bay boat ramp is expected to close to motorized vessels today, July 21. According to the park, it is likely that impacts to Signal Mountain marina and Leek’s Marina will occur as early as the end of August or early September.

The ramp will still be accessible to vessels that can be hand-carried.

The closures are based on the expected drawdown of Jackson Lake. Levels are expected to drop rapidly in the coming weeks to levels only seen three times in the last 30 years.

According to the Bureau of Reclamation, the reservoir currently is 71% full and 80% of normal storage for the date. The dam is currently releasing 5,250 cubic feet per second, which has been drawing down the reservoir at a rate of 3.5 to 4.5 inches per day. Current projections indicate the reservoir will continue to do so at a rate of 4.5-6.0 inches per day through the middle of September when the rate will likely be reduced to winter flows.

Due to drought conditions throughout the west, water supply in the form of reservoir storage is in critical need. The Jackson Lake Dam contractually provides irrigation and flood risk management for the Upper Snake Basin. This area includes southeastern Idaho, northwestern Wyoming, as well as small parts of Utah and Nevada. The Jackson Lake Dam raises the water level of the natural lake by 39 feet.

Recreation on the Snake River is also being affected. All river users are advised to be aware of higher than normal releases from the Jackson Lake Dam that will likely extend into September, before being reduced rapidly over the course of a few days to minimum winter flows. This will result in swifter currents than typical through August, and the possibility for new river hazards as flows decline.

As early as September, the river will become increasingly difficult for larger watercraft to navigate. As a result, scenic float trip operations will have shorter than historically typical operating seasons. Guided fishing operations may be affected as well.

Lindsay Vallen is a Community News Reporter covering a little bit of everything; with an interest in politics, wildlife, and amplifying community voices. Originally from the east coast, Lindsay has called Wilson, Wyoming home since 2017. In her free time, she enjoys snowboarding, hiking, cooking, and completing the Jackson Hole Daily crosswords.