Reports
Extent of brackish water in the tidal rivers of Maryland
1970, Webb, W.E. and Heidel, S.G.
Report of Investigations 13
Abstract
Fresh-water discharge, tide height and estuary size, shape, and salinity at the mouth are important controls on the extent of brackish water in tidal rivers (estuaries) of Maryland. Long-term predictions of the frequency or times at which brackish water will penetrate to a given section of an estuary are difficult because of the complex relations between the controls and the lack of quantitative predictions of the controls. Graphs and maps in the report show the historic extent of brackish water and may be used to estimate the probable extent of brackish water in the principal estuaries. For a distance of about 15 miles most of the estuaries will be brackish during one season, but will contain fresh water in the same section during another season of the year. In an estuary section containing a salt front, the water may be fresh at low tide but brackish at high tide. Extremes usually occur twice in 24 hours. The estuaries tributary to Chesapeake Bay usually contain relatively fresh water for 10 to 30 miles downstream from the point where tidal effect ceases. Data show that brackish water is flushed downstream by a sudden increase in discharge for a length of channel which will accommodate the volume discharged.
