Water Quality Indicators
The Water Quality Indicators (WQI) is a screening tool that makes it easy to identify pollutant hotspots based on water quality monitoring data from the U.S. Water Quality Portal Exit.
The WQI plots water monitoring locations and compares the values observed at these locations to a criteria or threshold. The color of the monitoring location shows whether the pollutant concentrations observed at the water monitoring location were above or below the threshold.
Access the Data
Current and historical data presented in the WQI can be downloaded from the WQI Data Downloads Folder.
Known Issues (Updated September 17, 2024)
- The Pollutant Change map layers are in the process of being updated with the most current data and no longer align with the WQI monitoring stations. The Pollutant Change map layers will be added to the WQI as soon as they are available.
- The trend chart at the bottom of a monitoring station’s pop up is currently loading very slowly. The ECHO Team is aware of the issue and actively working to improve the load times.
- The Chesapeake Bay Land cover layer currently displays yellow and blue checkered pattern in Washington DC and some parts of the Delmarva peninsula. This issue will be resolved in the next code deployment.
- The NLCD Land Cover layer's legend is currently not legible. This issue will be resolved in the next code deployment.
- The WQI is not optimized for use on mobile phones.
Purpose of WQI
WQI is an ambitious project designed to allow analysts to use large datasets to identify where water pollution hotspots occur. Prior to the launch of WQI, there had not been an easy way to visualize where high pollutant readings appear in streams, etc. EPA is working to add more pollutants to this project.
Nutrient Pollution
Ambient nutrient concentrations in water vary geographically and this should be considered when evaluating observed nutrient concentrations in the WQI. Additionally, nutrient contributions to the environment can come from a variety of point (e.g. wastewater treatment plants) and non-point sources (e.g. agricultural runoff). For more information on nutrient pollution, please see EPA’s Nutrient Pollution Website.
Pathogen Pollution
Various sources contribute pathogens to contaminated waters, including fecal pollution from humans, wildlife, and livestock. Elevated pathogen pollution can impact a water body’s ability to be used for drinking water and recreation. For more information on pathogen pollution’s impact on recreational water bodies, please see EPA's Recreational Water Quality Criteria and Methods webpage.
Caveats
Accuracy and utility
Please be advised that although these data have been processed successfully on a computer system at the U.S. EPA, no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. It is the responsibility of the user to read and evaluate the documentation and metadata files associated with these data to evaluate data set limitations, restrictions, and intended use. The U.S. EPA shall not be held liable for improper or incorrect use of the data. Neither EPA, EPA contractors, nor any organizations cooperating with EPA assume any responsibility for damages or other liabilities related to the accuracy, availability, use, or misuse of information provided on this website. EPA reserves the right to change information at any time without public notice.
Data included
The WQI presents the most recent ten years of data available in the Water Quality Portal for nutrients and several pathogen parameters (E. Coli, Enterococci, and Fecal Coliforms).
Data excluded
The WQI algorithm assesses the data for quality and completeness and does not use data determined to be incomplete. Please see Data Processing Summary below for a more detailed breakdown of the data processing for nutrient pollutants.
Subspecies phosphorus measurements are excluded
A suitable method for combining phosphorus subspecies into a total phosphorus measurement was not completed for the first release of the WQI. As a result, only measurements reported as total phosphorus (Characteristic names “Phosphorus” and “Phosphate-phosphorus”) were used.
Subspecies phosphorus measurements are excluded
A suitable method for combining phosphorus subspecies into a total phosphorus measurement was not completed for the first release of the WQI. As a result, only measurements reported as total phosphorus (Characteristic names “Phosphorus” and “Phosphate-phosphorus”) were used.
Criteria is used in the WQI Tool
To streamline the functionality of this screening tool, EPA used national 304(a) recommended criteria as an illustrative threshold for identifying pollutant hotspots. These include the national CWA 304(a) recommended criteria for nutrients, the 2012 Recreational Water Quality Criteria for E. Coli and Enterococci, and the 1976 “Red Book” Recreational and Shellfish Harvesting Criteria for Fecal Coliforms. The EPA publishes, and from time to time revises, recommended criteria for water quality under CWA Section 304(a) that accurately reflect the latest scientific knowledge, to provide guidance to states and authorized Tribes. The EPA’s 304(a) criteria recommendations do not impose legally binding requirements. They do not substitute for the CWA or EPA regulations, and they are not regulations themselves. Use of this screening tool does not imply any regulatory conclusions with respect to attainment of water quality criteria in effect under the Clean Water Act. EPA’s criteria recommendations are intended to assist state and Tribal authorities with the development of water quality criteria. States and authorized Tribes have the discretion under EPA’s regulations to adopt water quality criteria based on CWA Section 304(a) national recommended water quality criteria, those criteria modified to reflect site-specific conditions, or other scientifically defensible methods. To learn more about state specific water quality standards, please visit EPA's page on State-Specific Water Quality Standards Effective under the Clean Water Act (CWA).
Nutrient Data monitoring location included in the WQI Tool
Only nutrient data from river/stream or lake/reservoir water body types were included in the WQI tool. The 14 nutrient ecoregions cover only the lower 48 states and monitoring data from Alaska, Hawaii, Guam, etc. are not included in the WQI tool. Offshore monitoring locations with latitude/longitude outside the ecoregion boundaries are also bypassed.
Data Processing Summary
For a summary of the nutrient measurement records currently used in the WQI tool, please visit the WQI Data Usability Project page.