Spatial pattern and indicators of urban centralized drinking water sources quality violations in the Yellow River Basin

Drinking water safety is essential for the survival and health of human beings. Understanding water quality violations in urban centralized drinking water sources helps make policies to protect water sources towards improved drinking water safety. This study analyzed water quality of urban centralized drinking water sources in 53 prefecture-level cities in the Yellow River Basin in 2016-2020. The spatial patterns of quality violation and violation indicators were examined using statistical, hotspot and cluster methods. Anthropogenic and natural reasons that lead to quality violations of drinking water sources were discussed. The results indicated that 95.1% in the study samples complied with water quality standards. Drinking water sources from lake or reservoir have the lowest quality compliance rate of 90.6%. Water quality violations in drinking water sources presented spatial differences. Ningxia and southeast Gansu were hotspots of water quality violations. Sulfate, hardness, manganese, chloride and ammonia nitrogen were the main indicators that did not comply with the water quality standards in drinking water sources. The results are useful in improving the quality of urban centralized drinking water sources and ensuring drinking water security in the Yellow River Basin.