Reservoir Limited Wake Days

Starting in 2024, the city created “limited wake days” where on certain days and times large wake-creating activities, such as wakesurfing, are prohibited at the Reservoir during limited and no wake times. This operational adjustment will support the shared lake concept and help to reduce environmental impacts such as shoreline erosion.

Definitions

• Wake - A wake is a visible and turbulent trail left behind by a boat as it moves through the water. The wake is created by the displacement of water as the boat hull moves forward. In general, larger and heavier boats create larger wakes.
• Wake boat - Also known as a wakeboarding boat or wakesurf boat, these class 5 motorboats are designed for water sports activities that involve creating and riding on a large wake or wave. These boats are specifically engineered to produce a large consistent and well-shaped wake, making them suitable for wakeboarding, wakesurfing, and other water sports.
• Ski boats – A ski boat is designed to ride on a plane atop the water, making the smallest wake possible compared to a wake boat, which has ballast tanks to tilt the stern down to maximize water displacement and plow through the water, throwing up huge waves.
• Wakesurfing - Wakesurfing is a water sport where a rider trails behind a boat, riding the boat’s wake without being directly pulled by the boat. After getting up on the wake, typically by use of a tow rope, the wakesurfers will drop the rope and ride the steep face below the wave’s peak like surfing. Wakesurfing requires the boat to plow water at slow speeds versus boats operating on-plane.

What is a Limited Wake Day?

Historically, the Reservoir has had “no wake” times and “full wake” times to balance the needs of all lake users. Since 2021, Reservoir staff has been scheduling the lake in these two modes to manage the popularity of different water activities safely. Beginning in 2024, the Reservoir will have three modes of lake scheduling:

1. Shared Lake: The lake is open to all watercraft and all activities. Small craft are limited to the No-Wake Zone to limit potential for conflict with fast-moving power boats in the center of the lake.
2. No-Wake Lake: The lake is open to all watercraft, but power boats are not allowed to create a wake. This limits higher speed activities by power boats (no water skiing, wakeboarding or wakesurfing) during these times, allowing small craft to visit all areas of the lake safely. The schedule included 16 hours of No-Wake Time each week during the high season.
3. Limited Wake Days: The lake is open to all watercraft. Large wake-creating activities will be prohibited such as wakesurfing and wakeboarding.

What are the impacts of wakes on the Reservoir?

The Reservoir is a popular recreation area used for drinking water, recreation and irrigation. It is a shared space for various recreational activities. Large wakes have an impact on recreation users such as swimmers, rowers, anglers and paddleboarders. It is the city’s responsibility to balance all patrons’ recreational use of the Reservoir.

The Reservoir is a valuable drinking water supply for the City of Boulder. Water is collected and retained for municipal, domestic, agricultural, and industrial uses for members of the Northern Colorado Water Conservancy District (Northern Water).

Large wakes are one cause of shoreline erosion. The erosion of a shoreline can have significant impacts on a body of water, like the Reservoir.

Some of the impacts include:

• The destruction of plants and animal and microorganism’s habitats along the shoreline, which affects the biodiversity of the area.
• Erosion can also contribute to nutrient loading in the Reservoir, which can result in algal blooms, oxygen depletion, and negatively impact aquatic ecosystems.
• Sediment eroded from shorelines can enter the water, leading to increased turbidity, which degrades the Reservoir’s water quality and affects the growth of aquatic plants and fish habitats. Eroded sediment can also reduce the water storage capacity of the Reservoir and alter the water’s physical and chemical characteristics.
• Shoreline erosion under the boat ramps, which the city has observed at the Reservoir.
• Water quality can be impacted by large wakes, through spreading Eurasian Watermilfoil, an aquatic nuisance species discovered at the Reservoir in 2022.

The city realizes that there are multiple causes for shoreline erosion, such as large wakes from class 5 ballast boats. This operational change is one way we can control impacts that cause shoreline erosion.

Efforts to mitigate shoreline erosion include the implementation of erosion control measures, vegetation restoration, and sustainable land-use practices. The city and partners have invested significant resources to restore and repair Reservoir shorelines and will continue to monitor them annually.

How did you arrive at the decision to implement “limited wake hours?”

We use adaptive management principles to evaluate and continually improve services so we can best support all Reservoir users. The Reservoir operational assessment takes place through community engagement and research, which then becomes policy. Staff used this assessment tool, a measurable evaluation of shorelines and research to develop these changes.

Additionally, staff engage with the community through the annual facility evaluation and feedback as well as studying the best practices for the management of similar large bodies of water.

Limited wake times strike a balance between recreational boating activities and environmental conservation. It allows boaters to enjoy the Reservoir while promoting responsible use that minimizes ecological impact.

We explored alternative actions to the limited wake hours, such as creating a designated wakeboarding/wakesurfing area, but given the relatively small size of the Reservoir, this was deemed not feasible.

We want to emphasize that this is not a ban on wakesurfing as this change only applies when specialized wakesurf boats generate excessive wakes.