Prediction of Future Chlorophyll-a Concentrations in Large Eutrophic Shallow Lakes Under Multiple Stressors

Assessing future chlorophyll-a (Chl-a) changes is crucial for developing effective lake management programs. Future assessments should integrate socio-economic and climatic factors, including extreme climate impacts. However, such assessments are lacking. This study developed a novel framework and integrated model to analyze Chl-a response in Chaohu Lake to climate (e.g., precipitation, temperature, and wind) and socio-economic (e.g., population, fertilizer application, and livestock farming). The results indicated that by around 2050, the Chl-a concentration would change by −6.5% to −0.1% compared to around 2020. While socio-economic and climatic factors significantly altered nitrogen and phosphorus loading, exogenous loading had a minimal effect on Chl-a due to high endogenous releases. The decrease in Chl-a is mainly due to the increase in precipitation. Chl-a reduction was primarily driven by increased precipitation (0.6%–12.9%), leading to −9.4% to −4.4% Chl-a changes. The runoff increase also provided an opportunity to treat the heavily polluted lake area. Air temperature increases of 5.1%–9.2% resulted in Chl-a increases of 0.9%–3.1%. On annual scales the effects of precipitation and temperature were mainly due to changes in mean values. The effects of variability were significant at seasonal scales, for example, lower spring temperatures favored a decrease in summer Chl-a. There was uncertainty about the impact of future wind speeds. This study emphasized the importance of comprehensively quantifying the impacts of external pressures in lake water quality assessment and provided a reference and pathway support for the assessment and management of large, shallow lakes.