Spatial And Temporal Trends In Sediment Dynamics And Potential Aerobic Microbial Metabolism, Upper San Pedro River, Southeastern Arizona

Abstract

This study examines spatial and temporal variation in sediment dynamics and potential microbial respiration rates within parafluvial sediments of a point bar, Upper San Pedro River, Arizona. An innovative technique using seven colocated scour chains and real-time liquid-filled, load-cell scour sensors characterized sediment dynamics at the point bar during the monsoon season of July to September 2002. Stream/bar margins had the greatest scour while vegetated areas had the most deposition. Results from the 2002 monsoon season suggest that variation in sediment load is the dominant mechanism for scour and back fill sequences in the point bar setting for events < 1 year-flood. The vegetated site 52 m from the interface had higher respiration potentials from April through August than the stream-bar interface. Results illustrate that rates of microbial metabolism, comparable to those measured in the upper 20 cm below the water, extend to at least 85 cm below the water table.