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Discharges higher than are typically released from Alamo Dam in west-central Arizona were planned and released in 2005, 2006, 2007, 2008 and 2010 to study the effects of these releases on the Bill Williams River. The Bill Williams River Wildlife Refuge is located above the mouth of the Bill Williams River on Lake Havasu, and the river is the subject of ongoing ecological studies. Sediment concentrations and water discharges were measured in the Bill Williams River and turbidity, water temperature, specific conductance, pH, dissolved oxygen, and Secchi depth were measured in Lake Havasu during and after experimental releases in 2005 and 2006 from Alamo Dam. Additional measurements of the same parameters in the Bill Williams River and Lake Havasu were made during releases in 2010, and these are the subject of this report. Introduction On March 7, 2010, the Army Corps of Engineers, which operates Alamo Dam (fig. 1), initiated a release of about 3,000 ft3/s that lasted for 36 hours (fig. 2). Another high release was initiated on March 15, 2010, that had a peak discharge of about 2,000 ft3/s lasting about 157 hours (fig. 2). The U.S. Geological Survey (USGS) measured discharge and sampled suspended sediment at two locations on the Bill Williams River during the peak and on the rising and falling limbs of the first release. The USGS also measured turbidity and other physiochemical properties in Lake Havasu during both releases and after the recession of the second release. The USGS currently operates two streamflow gaging stations on the Bill Williams River that provide discharge data at 15-minute intervals. This report describes the measurement methods for discharge, suspended sediment, turbidity, and other physiochemical parameters and documents the measurement results. Information about the study area, previous and related work, and sediment, discharge, turbidity, and physiochemical data collected during high releases in 2005 and 2006 can be found in Wiele and others (2009). The inlets to the Central Arizona Project (CAP) canal and Wilmer Pumping Plant operated by CAP are located in Lake Havasu, and consequently the turbidity of the water in Lake Havasu is a major concern for the CAP. The CAP made additional turbidity measurements during the same time period as this study and presented them along with a discussion of the impacts of increased turbidity on their operation (Central Arizona Project,written commun., 2010). Acknowledgments The U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service supported the writing and publication of this report.