Turning Data into Information: the SMC’s Water Quality Index
The Southern California Stormwater Monitoring Coalition (SMC), a consortium of 14 different regulated and regulatory agencies, collects hundreds of samples and measures hundreds of indicators every year. The challenge is how to translate this avalanche of data into information that can be understood by non-technical experts, who are often the final management decision makers. This presentation describes the development of a Water Quality Index (WQI) that is both sensitive and responsive to changes in monitoring data, and is tied directly to the management questions of greatest interest to the SMC.
The SMC decided to focus the WQI on ecosystem health (i.e., aquatic life) beneficial uses. The WQI combines stressor data including chemistry and physical habitat quality, and response data including algal and invertebrate biological community health. For each metric of stress or response, an assessment index was created and converted to a normalized scale between zero and one. The assessment index for chemistry, focused on eight commonly measured chemicals, was based on probability of impacted biological communities. Similarly, the assessment index for physical habitat, narrowed to just seven key measurements, was also based on probability of impacted biological communities. The biological response metric included the California Stream Condition Index for invertebrates (CSCI) and the newly developed statewide assessment index for algal biological communities (ASCI).
The resulting WQI appears to be representing stream beneficial use conditions in a simple to understand, easily implemented, and report friendly format (i.e., reports of waste discharge, data dashboards, and reports to management). While the index rolls-up a tremendous amount of data, the information it contains is designed to be easily disassembled for more in-depth views. Of keen interest to users is the ability to compare stress versus response, which lends itself to management decision making such as beneficial use protection (unstressed and healthy), enhanced resiliency (stressed and healthy), impacted with known causes (stressed and unhealthy), and causal assessment required (unstressed and unhealthy). The SMC plans to begin using the WQI for regional stream monitoring beginning in 2019.