Bacteriological water quality in the Lake Pontchartrain basin, Louisiana, following Hurricanes Katrina and Rita, September 2005

The U.S. Geological Survey (USGS), in collaboration with the Louisiana Department of Environmental Quality, monitored bacteriological quality of water at 22 sites in and around Lake Pontchartrain, La., for three consecutive weeks beginning September 13, 2005, following hurricanes Katrina and Rita and the associated flooding. Samples were collected and analyzed by USGS personnel from the USGS Louisiana Water Science Center and the USGS Ohio Water Microbiology Laboratory. Fecal-indicator bacteria (Escherichia coli, enterococci, and fecal coliform) concentrations ranged from the detection limit to 36,000 colony-forming units per 100 milliliters. Data are presented in tabular form and as plots of data in the context of available historical data and water-quality standards and criteria for each site sampled. Quality-control data were reviewed to ensure that methods performed as expected in a mobile laboratory setting.