What preventative measure can help reduce algae blooms in water systems?

The correct answer focuses on ensuring proper disinfection and maintaining reservoir conditions, which are crucial for preventing algae blooms in water systems. Algae require specific conditions to thrive, including the presence of nutrients (such as phosphorus and nitrogen) and suitable environmental conditions, such as warm temperatures and stagnant water. By effectively disinfecting water and managing reservoir conditions—like controlling nutrient inputs and promoting healthy water circulation—water utilities can significantly hinder the growth of algae.

Proper disinfection helps to eliminate existing microorganisms, while maintaining ideal reservoir conditions includes practices such as monitoring water quality parameters and managing the water temperature and flow. These methods create an environment that is less conducive to rapid algae growth, thereby reducing the likelihood of harmful algal blooms that can compromise water quality and safety.

In contrast, increasing nutrient levels would directly promote algae growth rather than suppress it. Decreasing water temperature might limit some types of algae but doesn't address the underlying nutrient issues that typically lead to blooms. Adding recreational facilities near reservoirs can also introduce additional nutrient sources through runoff and may disturb the water balance, potentially exacerbating algae problems instead of mitigating them. Thus, the best approach to prevent algal blooms lies in proactive management of water quality through effective disinfection and reservoir condition maintenance.