CURRENT SCIENCE WORK BY THE US GEOLOGICAL SURVEY IN GRAND CANYON

There is a long and storied history of science work done by the US Geological Survey (USGS) in Grand Canyon. That tradition continues to this day with the USGS leading efforts in advancing understanding of the physical, biological, and cultural resources of the Colorado River in Grand Canyon through the Grand Canyon Monitoring and Research Center (GCMRC). Science information is collected by the GCMRC in support of adaptive management of the Glen Canyon Dam and is provided to decision-makers and the public to facilitate operations of the dam to improve, maintain, and conserve downstream resources.

Monitoring of sediment indicates that adaptive management of the Glen Canyon Dam through multiple years of experimental high flows has resulted in a majority of measured sandbars showing aggradation since 2012. Evaluation of aeolian dunefields adjacent to the river shows how these experimental flows are also benefiting the cover and protection of some archeological resources. Socioeconomic research has revealed that negative impacts to recreational resources and hydropower from normal operational flows or experimental flows have been consistently minimized.

Riparian vegetation surveys have led to detailed maps showing cover and extent, including invasive species such as tamarisk (Tamarix sp.). Observations of endangered humpback chub (Gila cypha) indicate that the adult population is currently stable and above levels requiring additional management action, while new populations are expanding in the Western Grand Canyon. In recent years, monitoring of non-native sport fish like rainbow trout (Oncorhynchus mykiss) in the Lees Ferry reach shows improvement in both abundance and condition. A new experimental flow implemented since 2018, called Macroinvertebrate Flows, was designed to improve aquatic food base conditions. Preliminary results indicate that this experiment may enhance insect diversity and abundance in areas of the Colorado River ecosystem.