DOES LOW DISCHARGE FROM THE DAM AT ST CROIX FALLS DAMN THE MUSSELS THERE?
The dam regulates water levels in both daily and annual cycles, and at times the discharge of the river is low enough that large swaths of the river bed are subaerially exposed.. We characterized these periods as low discharge events (LDEs) and used historical data (1983-Present) from the USGS to characterize the frequency and magnitude of these events to infer what impact they had on aquatic life, especially the mussel population. Our preliminary findings indicate that there have been many more LDEs in winter months than during the summer in recent years. We have been in dialogue with officials from the DNR and at the dam about the history of regulations regarding minimum discharge in order to determine whether potentially harmful low water levels were permissible given the standards at the time. We are also examining the relationship between discharge, temperature fluctuation and suspended organic solid concentration taken from on site measurements.