Tracking progress toward annual phosphorus (reducing hypoxia) metric: how it’s calculated

The U.S. and Canada adopted targets to reduce annual phosphorus loading by 40 percent from priority tributaries to control hypoxia in the central Lake Erie basin. Progress is calculated by comparing the average reduction from the 2008 load over the last five years toward the 40 percent reduction target.

A gauge indicator all the way to the left would indicate no reduction in average annual phosphorus loading, while an indicator gauge pointed all the way to the right would represent an average 40% reduction in annual phosphorus loading over the last five years.

Sample gauges showing progress toward 40% reduction goal

Progress is being tracked at three scales:

  • Lake Erie sub-basin: Gauge depicts phosphorus reductions from all Lake Erie Basin priority tributaries (phosphorus loads are summed and the average reduction is calculated)
  • State/provincial level: Gauge depicts phosphorus reductions from priority tributaries entirely or partially within individual jurisdiction (relevant phosphorus loads are summed and the average reduction is calculated)
  • Priority tributary: Progress toward the 40% reduction target at each priority tributary is shown beneath the gauge