TEMPORAL RELATIONSHIP BETWEEN DROUGHT-PRECIPITATION PATTERNS AND THE ONSET, DURATION, AND SEVERITY OF FRESHWATER HARMFUL ALGAL BLOOMS IN LAKE ALLATOONA, GA

Harmful algal blooms (HABs) increasingly threaten the freshwater supply through contamination and fish kill. These blooms occur annually in the eutrophic Lake Allatoona, and are affected by a number of interconnected physical drivers such as precipitation and drought. This study investigated the effect of precipitation dynamics on HAB onset, durations, and severity using satellite remote sensing and in situ datasets. Precipitation and streamflow data were obtained from USGS stations at Lake Allatoona for the years 2008-2014. Chlorophyll-a fluorescence data measured by the Georgia EPD in Allatoona and remotely sensed Landsat 8 scenes were collected for the same time span to calculate algal biomass. Statistical analyses including a Standardized Precipitation Index and Flow Duration Curves were conducted to determine the relationship between precipitation intensity, duration, and frequency and HAB growth. Landsat scenes were corrected and processed using a phycocyanin concentration detection algorithm to verify the presence of HABs associated with Chlorophyll-a data. These results suggest that the relationship between HAB growth and precipitation dynamics during the wet season is a function of bloom location within the lake. Blooms near the river inflow are disrupted by discharge events throughout the year and therefore can show reduced growth due to the increased wet season inflow (r² = 0.63). HABs in stable waters will be more likely have increased growth correlate to wet season precipitation intensity (r² = 0.78). Improved understanding of the relationship between precipitation and HAB growth will allow for greater prediction and remediation of freshwater resources.