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Browse History: Overview (2017)

A Tale of Two Rivers: Above-average Susquehanna River flow and nitrogen load, but below-average levels for the Potomac River

Nutrient loading related to river flow

The Susquehanna River is the single largest source of nitrogen and phosphorus discharging into Chesapeake Bay, and these nutrients drive the dissolved oxygen conditions in the mainstem. The amount of nutrients coming from the Susquehanna River is directly related to the amount of stream flow. 

Flow from the Susquehanna River in the winter-spring of 2017 was higher than average, especially during April and May. This means that there were slightly more nutrients flowing into the Bay during these months than in recent years. River flow and nutrient load from the Potomac River was well below average in the spring of 2017, especially in all months prior to May. Combined, these flows provided an average to slightly below-average amount of nutrients to the Bay that fuel algal blooms, and lead to low dissolved oxygen conditions. 

2017 Susquehanna and Potomac Rivers flow

Susquehanna and Potomac Rivers daily mean flow rates for January through mid-June 2017. Flow 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.

Nitrogen load from the Susquehanna River to the Bay
Nitrogen loads from the Susquehanna River were slightly above average for January through May, however, there was a large amount of nutrients entering the Bay during the high flow events in April and May (see graph below). The nitrogen loads are provided by the USGS and are used to forecast anoxia and hypoxia in the Bay. 

2017 Susquehanna and Potomac Rivers nitrogen load