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High flow and loads in spring 2011
Nutrient loading related to river flow
The Susquehanna River is the single largest source of nitrogen and phosphorus discharging into Chesapeake Bay. These nutrients have a significant effect on the dissolved oxygen and harmful algal bloom forecasts. Flow from the Susquehanna River in 2011 was characterized by several large peaks in late spring (March through May).
Provisional Susquehanna River total nitrogen loads (fall-line) for the January to April 2011 period were below average in January and February, then above average in March and April. These loads will affect the summer dissolved oxygen conditions. Based on the higher flow in May, May loads are expected to be above average as well. The higher-than-average nitrogen load estimates are one of the reasons the early summer anoxia forecast is moderately large.
Provisional Potomac River total nitrogen loads (fall-line) for the January to April 2011 period followed a similar pattern to the Susquehanna River loads. Below average loads in January and February then increased to above average loads in March and April. These Potomac loads factor into the early summer anoxia forecast.
Potomac River total nitrogen loads (fall-line) for the period of January to April for 2011 and the long-term average for the same months. Provisional data supplied by USGS.
The forecasts do not account for unseasonable June and July conditions, but represent the best available prediction based on past and present conditions.
This summer it is predicted that:
The late summer anoxic volume (no dissolved oxygen) in the Bay's mainstem is predicted to be moderate to large this summer, with the average late summer anoxic volume forecasted to be 2.4 ± 0.9 km3. Compared to the previous 26 summers, late summer 2011 could have the 5th largest anoxic volume for the period of record if this prediction holds true.
The hypoxic volume (low dissolved oxygen) in the Bay's mainstem in July is predicted to be moderate to large this summer, with the average July hypoxic volume forecasted to be 9.7 ± 1.1 km3. Compared to the previous 26 summers, July 2011 could have the 6th largest hypoxic volume for the period of record if this prediction holds true.