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1948 2006 MainstemTemp.jpg

Prior to completion of Glen Canyon Dam in 1963, the temperature of water flowing through the Grand Canyon each year was highly variable, ranging from the icy, spring run-off to the warm, 85-degree summer-heated flows. However, once the dam was constructed, the temperature of the water released from the dam - drawn from the depths of Lake Powell and released through the dam's penstock intakes - ranged for many years between 45 and 50 F (7 to 10 C). With the lowering of Lake Powell, release temperatures have been increased to as high as 59 F (15 C) which has likely led to an increase in the humpback chub and other native fish populations in Grand Canyon.

These increases in temperature, however, also increase the risk of expanding the distribution and abundance of cool/warm-water nonnative fish like brown trout, green sunfish, smallmouth bass, and walleye which could have a devastating impact on the humpback chub population in Grand Canyon like they have on humpback chub and other native fish populations in the Upper Basin.



2016 ModeledRiverTemps.jpg

The timing of seasonally warm release temperatures and high summer air temperatures have a large influence on downstream river temperatures. The warmest release temperatures occur in late October/early November but the greatest potential of warming the river in Grand Canyon occurs in July and September when air temperatures are the hottest. The reason is that it takes a lot longer to warm all the water in Lake Powell vs the water in the river as it flows downstream through the canyon.

Another thing to note that during the winter, river temperatures actually cool with distance downstream because releases are actually warmer than ambient air temperatures.

Temperature bl LCR 1990 2015.jpg

Increasing Water Temperatures at the Little Colorado River Confluence (RM 61), 1990-2015

Links and Information

Temperature Gages

Papers and presentations






Other Stuff