Multiple Al applications over a period of 10-12 years are planned for Cedar Lake in order to control internal phosphorus loading. It is critical to conduct post-treatment monitoring of water and sediment chemistry to document the trajectory of water quality improvement during rehabilitation to make informed decisions regarding adjusting management to meet future water quality goals. Post-treatment monitoring included field and laboratory research to document changes in 1) hydrology and watershed phosphorus (P) loading, 2) the P budget and lake water quality, 3) binding of sediment mobile P fractions that have contributed to internal P loading by alum, and 4) rates of diffusive P flux from the sediment under anaerobic conditions. Overall, lake water quality is predicted to respond to watershed and internal P loading reduction with lower surface concentrations of total P and chlorophyll concentrations throughout the summer, lower bloom frequency of nuisance chlorophyll levels, and higher water transparency.

Multiple Al applications over a period of 12 years are planned for Cedar Lake in order to control internal phosphorus loading. It is critical to conduct post-treatment monitoring of water and sediment chemistry to document the trajectory of water quality improvement during rehabilitation to make informed decisions regarding adjusting management to meet future water quality goals. Post-treatment monitoring included field and laboratory research to document changes in 1) hydrology and watershed phosphorus (P) loading, 2) the P budget and lake water quality, 3) binding of sediment mobile P fractions that have contributed to internal P loading by alum, and 4) rates of diffusive P flux from the sediment under anaerobic conditions. Overall, lake water quality is predicted to respond to watershed and internal P loading reduction with lower surface concentrations of total P and chlorophyll concentrations throughout the summer, lower bloom frequency of nuisance chlorophyll levels, and higher water transparency. Multiple Al applications between 2017 and 2029 should result in the binding of iron-bound P and substantial reduction in diffusive P flux from sediments under anaerobic conditions (i.e., internal P loading). The objectives of this interim report were to describe the 2018 limnological and sediment variable response to the 2017 alum treatment in Cedar Lake.

Multiple Al applications over a period of 12 years are planned for Cedar Lake in order to control internal phosphorus loading. It is critical to conduct post-treatment monitoring of water and sediment chemistry to document the trajectory of water quality improvement during rehabilitation to make informed decisions regarding adjusting management to meet future water quality goals. Post-treatment monitoring included field and laboratory research to document changes in 1) hydrology and watershed phosphorus loading, 2) the phosphorus budget and lake water quality, 3) binding of sediment mobile phosphorus fractions that have contributed to internal phosphorus loading by alum, and 4) rates of diffusive phosphorus flux from the sediment under anaerobic conditions. Overall, lake water quality is predicted to respond to watershed and internal phosphorus loading reduction with lower total phosphorus and chlorophyll concentrations throughout the summer, lower bloom frequency of nuisance chlorophyll levels, and higher water transparency. Multiple Al applications between 2017 and 2029 should result in the binding of iron-bound phosphorus and substantial reduction in diffusive phosphorus flux from sediments under anaerobic conditions (i.e., internal phosphorus loading).

Cedar Lake Protection and Rehabilitation District is sponsoring a two phase Lake Management Planning project to conduct tributary, in-lake and sediment monitoring to measure effectiveness of alum treatment. Project activities include: Phase one flow measurements; collection and analysis of grab and integrated samples; sediment cores collection and analyses for vertical and spatial variation in sediment characteristics; laboratory-derived rates of phosphorus release (3 samples from centrally located station); committee meetings for plan development.