What do the scores mean?

Blue Water Baltimore uses Maryland Tributary Assessment (MTAC) protocol to calculate annual Bacteria and Ecosystem Health scores for each of the parameters we monitor. Readings for each sampling day are assessed according to these criteria, and the scores you see here are rolled up annual averages. Each scores is out of a possible 100 points, where 100% means the site achieved the highest bar for water health every time it was sampled.

Bacteria

Bacteria is scored according to a traditional academic scale, and these ranges are indicative of the annual relative risk of people becoming sick from swimming at a certain location. 0-59% is “very poor”; 60-69% = “poor”; 70-79% = “moderately poor”; 80-89% = “moderate”; 90-99% = “good”; and 100% = excellent, where bacteria readings passed the established COMAR safe-swimming threshold every single time it was sampled that year.

EcoScore

A station’s overall ecological health score, or “EcoScore,” is calculated by averaging together the scores for each parameter monitored throughout the year. These data are assessed on ecologically relevant thresholds, like when dissolved oxygen levels preclude crabs from living in the water; or when specific conductance starts affecting dragonfly larvae in our streams. Parameter and Overall EcoScores are developed according to a quintile scale, which is different from a traditional grading scale. 0-19% is “very poor”; 20-39% = “poor”; 40-59% = “moderate”; 60-79% = “good”; and 80-100% = “very good.”