Further Studies of Surface Winds near Glen Canyon Dam, Arizona

Hypotheses have been proposed for the Glen Canyon wind regime, which is contrary to the mountain valley flows that might be expected to follow the historical Colorado River channel, 1) that the observed wind regime is a return flow; and that 2) the observed winds are driven by temperature differences between Lake Powell and the surrounding terrain. The results of measurements made to test these hypotheses are presented. The measurements were found not to support the hypothesis that the Glen Canyon winds are a return flow to a mountain-valley circulation occurring in a lower level. The hypothesis of lake-driven flows seems to describe the winds measured at the Glen Canyon Dam. Apparently, the night-time southwesterlies are a density flow from the cooler surrounding terrain to the warmer lake (lake water surface temperature average 8 degrees C in winter). As the terrain warms during the day, the wind reverses and blows from the cooler lake towards the warmer terrain.