Flow levels and water temperatures taken from USGS flow gauges around the Upper Colorado River watershed.
Water temperatures were high across most of the Upper Colorado River Watershed in July,
with low flows in key parts of the watershed from trans-basin diversions. Over 500 cubic feet per second (CFS) were diverted to the Front Range through the Moffat and Adams tunnels, marked by the purple lines on the right side of the map.
Flows at Windy Gap represent water sent further downstream, with only 176 cfs flowing further down the Colorado in mid-July. The red dot to the left of Granby marks Windy Gap Reservoir, where the two major confluences of the Upper Colorado River – the North Fork and the Fraser – meet.
Green plus signs mark areas in the watershed with lower water temperatures, where fish won’t already be stressed by water conditions, while the yellow and red crosses on the map mark areas in the watershed that should only be fished in the morning, before the heat of the day, or not at all.
Knowing water temperatures is key when it comes to fly fishing. Trout are cold water fish, which means they experience stress at higher water temperatures. Catch-and-release fishing on a stream or waterway with elevated temperatures can kill trout already stressed from the warm waters.