April 15 - September 30, although not all ramps are open yet, as I was just there 2 days ago... See link:. https://www.canyonco.org/project/lake-lowell-park/#:~:text=Motorized%20and%20Non%2Dmotorized%20boating,for%20migrating%20and%20wintering%20wildlife.
I believe it's open to boats on the 15th of April officially?? Don't quote me on it?? I just googled it.
I'm uncertain, I see boats on the lake now.
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