River flows into the Chesapeake, which has been below average since August, remained lower than normal in April, according to the U.S. Geological Survey.
Average April flows into the Bay are 93.4 billion gallons a day, but this year’s flow was only 63.8 bgd, or 32 percent below the long-term average measured by USGS since 1951.
Historically, low flows are good news for water quality because they wash fewer nutrients and sediments into the Bay. The nutrients fuel algae blooms, which eventually die and sink to the bottom, depleting the water of oxygen. Algae and sediment also cloud the water, blocking sunlight to underwater grass beds that provide important habitat for juvenile fish, blue crabs, clams and waterfowl.
This year has followed that pattern, according to Bay Program water quality monitoring. Through April, oxygen levels in deep portions of the Bay remained high. And, as of mid-May, there were no signs of major algae blooms in the Chesapeake.
While low freshwater flows are generally good news for water quality, they can be bad news for oysters because high salinity waters promote the spread of deadly diseases. Also, higher salinities will mean more stinging jellyfish in the Bay during summer months.
The dry spell which has lasted since last summer follows a record-setting wet period during first six months of 1998, when more freshwater flowed into the Bay than any other six-month period on record.