The combination of wildfire smoke deposition and El Niño-driven weather changes poses risks to water quality in U.S. lakes and reservoirs. Warmer winters may reduce ice cover and limit deep water reoxygenation, increasing the likelihood of hypoxia and internal nutrient recycling. This could lead to harmful algal blooms, which threaten aquatic ecosystems, drinking water supplies, and recreational activities. Reservoir managers are particularly concerned about the long-term impacts, as these conditions can persist for years, as evidenced by Lake Superior's ongoing challenges with cyanobacterial blooms.