Colorado state parks: Spinney Mountain

Next up in our series exploring Colorado’s state parks is Spinney Mountain! Spinney Mountain State Park features a 2,500 surface acre reservoir located along the South Platte River in Park County. The reservoir is nationally renowned as an excellent location for fishing and boating.

Spinney Mountain State Park was created in early 1980s after the completion of the Spinney Mountain Dam. While the park is managed by Colorado Parks & Wildlife (CPW), the reservoir and surrounding land are owned by the City of Aurora. The reservoir serves a dual purpose, providing both outdoor recreation opportunities and most of Aurora’s water supply.

Spinney Mountain Reservoir and the South Platte River below are designated by CPW as a “gold medal water” for their exceptional trout and northern pike fishing. CPW stocks the reservoir with cutthroat, rainbow, and brown trout. They also carefully manage the northern pike population because these larger fish have a habit of eating the stocked trout. For more information about CPW’s management strategy, take a look at the Spinney Mountain Reservoir Fisheries Management Plan and their fish stocking schedules.

Northern pike aren’t the only species threatening Spinney Mountain’s trout population. The reservoir is the site of a New Zealand mudsnail infestation. New Zealand mudsnails are an invasive species of tiny freshwater snails, ranging in size from a grain of sand to 1/8 inch long with black or brown spiral shells. Mudsnail populations grow rapidly and they can reproduce asexually, meaning that only one snail can start a whole new population. The snails are insatiable eaters, outcompeting native mollusks and invertebrates for food resources. The reduced invertebrate population means less food for the larger fish and animals, disrupting the reservoir’s entire ecosystem. Trout and northern pike try to eat mudsnails, but they can pass through a fish’s digestive system unharmed because of their protective shells. The snails are nearly impossible to contain once they are introduced to a waterway, so it’s crucial to follow CPW’s Aquatic Nuisance Species guidelines to keep them out of Colorado’s uninfested waters.

If fishing isn’t your preferred aquatic activity, the reservoir is open for boating of all kinds. Wind surfing is a popular activity at Spinney Mountain; wind can reach speeds of 30-40 miles per hour on the water, creating waves up to five feet! Full-body wetsuits are recommended for anyone enjoying the cold water of Spinney Mountain’s high-altitude reservoir.