Monitoring of Sediment Volume in Bedrock Stream Pools (tinajas) in Saguaro National Park, 2005-2010

Pruden, Chris; Perger, Chuck; Swann, Don; Ratzlaff, Kris

Bedrock stream pools (also called tinajas) in Saguaro National Park’s Rincon Mountain District are critical habitat for wildlife and an important indicator of ecosystem health. Wildfires, floods, and the sedimentation of pools and stream channels are part of the natural hydrologic process of this region. However, years of fire suppression appear to have increased fire intensity and postfire flooding, which have in turn greatly increased the amount of sediment in tinajas. In 2005, Saguaro National Park initiated a monitoring program to track the long-term dynamics of sediment in tinajas and better understand the connection between fire events and stream dynamics. Results of surveys of 24 tinajas conducted during 2005- 2006, 2007, and 2010 confirm that large sediment loads following fires move through streams very slowly, on the order of decades rather than years. The data also suggest that major floods, such as occurred in 2006, are also important drivers of sedimentation patterns on a local scale. These surveys have enhanced our knowledge of stream dynamics throughout the Rincons, and have the potential to help us better understand the time scale of these changes in relation to fire events in the arid Southwest.