The study evaluated the water quality security of reservoir-based drinking water sources in Chongqing City. Researchers assessed the water quality classification, eutrophic state, healthy risk, and pollution levels of these sources. They used the analytical hierarchy process to comprehensively evaluate water security. The results showed that 97 percent of the reservoir-based drinking water sources in Chongqing City met the standard for water quality, indicating good water quality overall. This information can help guide the protection and management of drinking water sources in the area.