The Green and Colorado rivers are among the most significant and valued resources in Canyonlands National Park. During the past 50 years, upstream dams and water withdrawals have greatly altered streamflow patterns in both rivers. During the same period, the river corridors became densely vegetated by invasive exotic tamarisk (Tamarix sp.). Altered streamflow patterns and dominance by exotic tamarisk together have adversely impacted many of the rivers' dynamic natural characteristics, including habitat conditions for endangered native fish and the creation and modification of unvegetated islands and sand bars.
The purpose of this trench at Hardscrabble Bottom is to expose deposits of river sediment that scientists can date by various methods including counting of growth rings found in buried stems of tamarisk. Dated sediment deposits then can be related to past patterns of streamflow recorded by the streamgauge at Green River, Utah, and to past patterns of vegetation establishment recorded in rings of tamarisk and other woody plants. By integrating this information with data obtained from other sources such as repeat aerial photography, scientists will gain insights into processes and rates of change in natural characteristics of the Green River in Canyonlands.
This research is one component of a larger program of scientific research that seeks to understand the effects of changing streamflow regimes on sediment-transport processes, channel characteristics, and the quality of aquatic and riparian habitats along the Green and Colorado rivers in the park.
Resulting information can be used by scientists and National Park Service managers to predict the potential consequences of future changes in streamflow that may be attributable to climate change or increasing societal demands on water flowing in the Green and Colorado rivers.