Water Quality Index

The Water Quality Index (WQI) is a tool developed to better communicate water quality information in a concise and understandable way. The WQI generates a single standardized number reported on a scale from 0 to 100, with 100 representing high water quality. To achieve a top score the samples must have uniform attainment of water quality standards.

How is it measured?

The general index considers the percentage chemical parameters exhibiting exceedances of water quality standards, the percentage of samples exhibiting exceedances of water quality standards, and the magnitude exceedences over the water quality standard. For more details see: McCarty, D. 2018. The Arizona Water Quality Index: A Communications Tool for Water Quality Summaries. Arizona Department of Environmental Quality.