Temperatures in lower Grand Canyon have also been somewhat warmer than in the past.
At the Diamond Gage station, Colorado River mile 225, in-stream summer temperatures are similar to 2003, but not as warm as 2000 during the Low Steady Summer Flows experiment, where discharge was held to 8,000 cfs throughout the summer months. During high and fluctuating flows as in 2003 and 2004 (Flow minimas around 10,000 cfs, highs around 18,000 cfs), less warming occurred as the water flowed down Grand Canyon.
While river temperatures began to warm in 2003 and 2004 in the spring; the commencement of higher flows in June retarded further warming. As flows decreased in September of 2003, greater warming was realized. Flows from Glen Canyon Dam in September 2004 will average 8,000 cfs, allowing for greater downstream warming.
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