In 2010 the overall health of the Potomac River decreased from a 49% score in 2009 to 34%. This decline in score is likely due to several factors such as high stream flow in late winter and early spring. While total stream flow to the Chesapeake Bay was within the normal range during the 2010 water year, the Potomac River daily flow was frequently higher than average, especially during the late winter. This high flow was caused by two major storm events on January 27 and March 15, 2010. It is unusual to have two very high flow events so close together followed by a prolonged period of lower than average flow in late spring and summer, thus making this streamflow pattern unique.
