How was the health of Guanabara Bay calculated?

Environmental report cards are used by resource managers to assess and report on the ecosystem health of a region. Developing rigorous, quantitative assessments provides accountability to support environmental protection efforts. A five-step process of developing report cards is used to assess progress: 1) determine values and threats, 2) choose indicators, 3) define thresholds, 4) calculate scores, and 5) communicate results.

This report card provides a transparent, timely, and geographically detailed assessment of health in Guanabara’s Bay and Basin using data from 2013-2015 collected by State Institute of the Environment (INEA). Guanabara Bay health and Guanabara Basin health are defined as the progress of five indicators toward scientifically-derived thresholds or goals. The indicators are combined into two water quality scores, one score for the Bay, and one for the Basin.

Each sample is compared to a threshold to calculate a score from 0 to 100. All sample scores are averaged for each sampling location to reach a station score. All stations in each region are averaged to a region score. All regions are averaged to the overall indicator score.

Overall Health Index

The Guanabara Bay report card compares 5 indicators for the Bay (dissolved oxygen, biological oxygen demand, total phosphorus, dissolved inorganic nitrogen, fecal coliform) and 5 indicators for the Basin (dissolved oxygen, biological oxygen demand, orthophosphate, dissolved inorganic nitrogen, turbidity) to scientifically derived thresholds or goals. These indicators are combined into two Water Quality Indices (one for the Bay and one for the Basin). The data was provided by INEA.