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Impact of Seasons, Nutrient Pulse, and Mississippi River Flood of the Spring-Summer of 2011 on Water Quality in the Atchafalaya Basin, Louisiana

Douglas Carlson and Marty Horn
Louisiana Geological Survey – Louisiana State University,
3079 Energy, Coast and Environment Bldg., Baton Rouge, Louisiana 70803–0001

Water quality of the Atchafalaya Basin was analyzed from 11 sampling events between May 19 and October 12, 2011. Water quality was influenced by seasonal temperature variations, a nutrient pulse attendant with surface runoff, and by the Mississippi flood of May through July of 2011.

Seasons impacted temperature, concentrations of chloride and sulfate, and electrical conductance. Temperature increased from May to early August, then declined until October. Sulfate concentration and electrical conductance increased from May until October as the share of water from the Missouri River increased from approximately 20% in May to nearly 60% in October. Nutrients of nitrate and phosphate were influenced by the pulse of nutrients due to runoff from cropland in the Missouri River, Ohio River, and Upper Mississippi River basins. Nutrient concentrations tended to remain high May through July and then declined to lower values in August through October. The Mississippi River flood of May through July generally caused concentrations of nitrate and phosphate to decrease during the flood event and then recover to pre-flood conditions by late July when the flood crest passed through the Atchafalaya Basin.


AAPG Search and Discovery Article #90158©2012 GCAGS and GC-SEPM 6nd Annual Convention, Austin, Texas, 21-24 October 2012