The City of Montrose got itself a new whitewater park in 2015. It features a set of six distinct features that change a fair bit at different flows (which are a little complicated to figure out, see below) but provide surfable features at a wide variety of flows, and which are surfable later into the season than a lot of other areas thanks to irrigation needs and water calls in the area. You’ll start to find something to surf as low as 200-250 cfs, and things stay good over 750 and likely well above. Even at lower flows, you’ll find a couple green waves that will work for SUPs, though you may have a hard time staying on the low-flow features on a shortboard.
Due to irrigation needs in the area, the Montrose park holds decent flows into the late summer and fall, a rarity in Colorado. There is enough plumbing in the area that the closest gauge doesn’t give a very accurate picture of the flow, but fortunately the Town of Montrose maintains an “Estimated Flow” figure on their website here; it’s the best source of flow information.
Park at Baldridge Park in Montrose and the features will be directly in front of you in the river.