The recurrence of harmful algal blooms in the Western Lake Erie Basin is mainly attributed to an increase in soluble nutrients. The consensus is that this is mainly coming from the agricultural lands of the Lake Erie watersheds. While current efforts are geared toward achieving nutrient reduction, the effects of climate change on these reduction strategies have not been fully understood. This case study quantified levels of nutrients and the corresponding algal bloom severity under different future climate scenarios and mitigation practices.
The economy of Lake Erie, one of the Great Lakes in northern America, is valued at $10billion/year; mainly from tourism and travel. However, recurring harmful algal blooms (HABs) in the western basin and hypoxia in the central basin have had a detrimental impact. With the predicted increases in temperature and precipitation, future recurrences of HABs are likely to get worse. Therefore, it is vital to identify best management practices and estimate the future severity of HABs.
Historical data for daily precipitation, and maximum and minimum temperatures were downloaded from the Copernicus Climate Change Service (C3S) Climate Data Store (CDS). A computer model was then used to accurately simulate historical daily stream discharge and sediment levels. Next, local climate impact indicators (CIIs) were produced, including simulated stream discharge, nutrient levels, and sediment exports.
Flow, sediment, nutrient, and climate data were then input into an algal bloom model. Finally, the impact of nutrient and sediment load reduction strategies with different climate scenarios were evaluated.
The results showed that raised temperatures and precipitation levels would increase the annual occurrence of severe algal blooms. The implementation of best management practices would keep the risk at its current level, but additional mitigation would be needed to further reduce the risks.
The information from this case study could help better inform and prepare stakeholders including farmers, government agencies and policymakers against the effects of climate change.
National Center for Water Quality Research (NCWQR), Heidelberg University, Ohio, US