Poster 209 – Click on poster below to view presentation from author.
Osama Tarabih
University of South Florida Tampa
Co-Authors: Mauricio Arias
Water management operations can drive long-term water quality patterns in nutrient-enriched lakes and reservoirs. This study identified multidecadal trends of rainfall, flow, water levels, total phosphorous (TP), total nitrogen (TN), and Chlorophyll-a in the water column and eight (dis)tributaries during four specific operation schedules (1974–1990, 1991–1999, 2000–2007, and 2008–2019) in Lake Okeechobee (Florida). We found an increasing trend in water discharges towards the Gulf of Mexico (via the Caloosahatchee River) during the dry season for the entire 46 years, and a decreasing trend in discharges towards the Atlantic Ocean (via the St. Lucie Canal) during 2008–2019. Higher flows, combined with increasing TP concentrations in the lake and the Caloosahatchee, led to significant increases in monthly TP mass loads to the Gulf of Mexico by up to 122%–158% during 2008–2019. Higher flows in the Caloosahatchee also resulted in a net TN load increase to the Gulf, despite system-wide decreases in TN concentrations. Overall, results from this study demonstrate that reservoir operations could have long-term effects on nutrient status and exports; thus, modifying operations should be considered as a potential nutrient management tool.
Post comments and questions for author below.
All posts are publicly visible after review by site administrator. Students’ responses to posted questions is factored into scoring for the poster competition. Finalists announced May 25 and awards presented May 26, 2021.
Virtual Poster Symposium 
Thanks for sharing your work. Can you further comment on the reservoir operations? Are changes in operations suggested from this work?
LikeLike
Thanks for your interest in my poster. We found that there are relationships between flow patterns and nutrients in the Lake and the distributaries. For instance, we found that TP concentrations in Lake Okeechobee and the distributaries were lower during the 1978 Rules and Run 25 operation schedules, which was associated with more water discharges during the dry season and less discharges during the wet season. However, those relationships were not statistically evaluated. Thus, we did not suggest specific changes in the operations, but we recommend that nutrient reduction should be incorporated as a target in the operation schedules.
LikeLike
Thank you for your presentation. Besides changes in discharge patterns/schedules from the lake, what other factors do you think may have contributed to increases in TP and decreases in TN loading over the last several decades?
LikeLike
Thank you for your comment. Regarding Phosphorus, the increasing trends in TP loadings into the distributaries are probably associated with the increasing trends in the Lake which are probably because of internal loadings from the Lake’s bed sediments. While, the reductions in TN loadings in the Lake and the distributaries are probably associated with fertilizer reductions in the region (10%-50%) associated with irrigation improvements and fertigation best management practices.
LikeLike