Each year, the Virginia Institute of Marine Science and Anchor QEA, LLC release a retrospective seasonal analysis of the severity of hypoxia in the Chesapeake Bay. The Annual Chesapeake Bay Hypoxia Report Card summarizes dissolved oxygen concentrations in the Bay as estimated by the team's 3-D, real-time hypoxia forecast model. The modeling team also generates the same dissolved oxygen statistics for previous years for comparative purposes.
The Maryland Department of Natural Resources also prepared an annual hypoxia report that presents a similar interpretation of hypoxia in 2018.
Report Card Metrics
The forecast and report card use multiple metrics to quantify and compare hypoxic severity:
Synopsis for 2018
Springtime inflows from the Susquehanna River were high in 2018, resulting in the prediction that 2018 would have an above average amount of hypoxia. However, wind speed and direction also play a large role in the severity of hypoxia during the summer. During 2018, the total annual hypoxic volume was similar to 2014 and 2017 through mid-July, but larger than in 2015 and 2016. Strong winds in the second half of July reduced the amount of hypoxia to near zero. Hypoxia increased rapidly again in early August and peaked at a higher value in early September than in previous years. Strong winds in September again mixed Bay waters, resulting in a large reduction in hypoxic volume. Overall, the total amount of hypoxia in 2018 was estimated to be similar to 2017, but the seasonal patterns in hypoxia were very different. Hypoxia was estimated to start earlier and last longer in 2018 than in recent years. The lack of hypoxia in late July was very atypical of historical dissolved oxygen conditions, but consistent with the report released from Maryland Department of Natural Resources for the Maryland portion of the Bay.
Summed Annual Estimates
Here we describe the severity of hypoxia as estimated by the forecast model. We define hypoxia as dissolved oxygen concentrations less than 2 milligrams/Liter (mg/L). Duration refers to the number of days the Bay experiences hypoxic conditions exceeding 2 cubic kilometers (km3) in volume.
Time Series Estimates
Strong winds in the second half of July reduced the amount of hypoxia to near zero. Hypoxia increased rapidly again in early August and peaked at a higher value in early September than in previous years. Strong winds in September again mixed Bay waters, resulting in a large reduction in hypoxic volume.