Nearshore thermal gradients of the Colorado River near the Little Colorado River confluence, Grand Canyon National Park, Arizona, 2010

A study of the Colorado River near its confluence with the Little Colorado River in Grand Canyon National Park found no significant thermal gradients between nearshore environments and the mainstem, despite expectations that such gradients could influence fish habitat-seeking behavior. The research, conducted over 10 to 27-day periods in summer and fall 2010 across four geomorphic unit types, used high-precision instruments (0.2°C accuracy) but detected no persistent temperature differences greater than this threshold. This lack of substantial gradients contrasts with the known importance of thermal variability for native fish species, such as the endangered humpback chub, which are adapted to warmer, seasonal water conditions. The study highlights the limited understanding of nearshore thermal dynamics in dam-regulated river systems and their potential ecological implications.

Ross, R., & Grams, P. E. (2013). Nearshore thermal gradients of the Colorado River near the Little Colorado River confluence, Grand Canyon National Park, Arizona, 2010. Open-File Report. https://doi.org/10.3133/ofr20131013