Hydrographic properties across the mouth of Chesapeake Bay has been monitored by the Center for Coastal Physical Oceanography (CCPO) with support from the Department of Earth, Ocean and Atmospheric Sciences at Old Dominion University since April 1992.

Cruises have been scheduled almost every month on the spring tidal cycle for the past sixteen years, 152 cruises have been completed up to September 2007. During each cruise, hydrographic profiles are obtained at twenty individual stations in a line approximately parallel to the Chesapeake Bay Bridge-Tunnel. The first station starts at the southern part of the bay mouth near Norfolk and the section continues northward toward Cape Charles. Each station is placed roughly one nautical mile (1.8 km) apart from the other.

At each station, a Sea-Bird Electronics (SBE) 25 SEALOGGER CTD (conductivity, temperature, and depth) or a SBE 19 SEACAT Profiler CTD is slowly lowered at several seconds per meter down through the water column until the instrument is within one meter of the bay floor. As the CTD is lowered it records the depth in meters, temperature (°c), and conductivity (Siemens/m). Finally, the raw CTD data were corrected and salinity (psu) determined using the SBE Data Processing software. The data where averaged over 1 meter intervals.



Figure. Hydrographic section across the Bay mouth. The stations are indicated. The 25 km wide bay mouth contains three main channels that allow the exchange of fresh water and salt water between the bay and the coastal ocean. The Beach Channel located in the north, the Chesapeake Channel in the middle, and finally the Thimble Shoal Channel in the south.