Plume and Bloom: Effect of the Mississippi River Diversion on the Water Quality of Lake Pontchartrain
Mishra, D. R., & Mishra, S. (2010). Plume and Bloom: Effect of the Mississippi River Diversion on the Water Quality of Lake Pontchartrain. Geocarto International. 25(7), 555-568.
The Opening of one of the Mississippi River diversions, Bonnet Carré spillway, to prevent flood threat to the city of New Orleans in April 2008 created a sediment plume in the Lake Pontchartrain. The nutrient rich sediment plume triggered a massive algal bloom in the lake that started in mid-May 2008 and persisted through July 2008. In this paper, we have quantified and mapped the spatio-temporal distribution of sediment plume (suspended solids) and algal bloom (chlorophyll-a) in the lake after the spillway opening using remotely sensed data and studied the relationship between them. We processed the Moderate-resolution Imaging Spectroradiometer (MODIS) data for mapping the total suspended solids (TSS) and chlorophyll-a concentration in the lake. An existing algorithm was used for estimating TSS concentration whereas a novel slope algorithm was developed to predict the per-pixel chlorophyll-a concentration. Both algorithms were successful in capturing the spatio-temporal trend of TSS and chlorophyll-a concentrations respectively. Algal growth was found to be inversely related to TSS concentrations and a time lag of approximately 45 days existed between the spillway opening and the appearance of the first algal bloom at an observation location.