Deep-Channel Designated Use 
“Tidally influenced waters at depths greater than the measured lower boundary of 
the pycnocline in isolated deep channels.” U.S. EPA 2003, Appendix A, page A- 
6 . 
Mesohaline Segments Expanded Designated Uses 
Using the time period 1991 -2000 1 , depth profiles of change in density and dissolved oxygen 
concentrations from the Chesapeake Bay Water Quality Monitoring Program 2 were reviewed for 
both evidence of stratification and prevention of re-oxygenation. Chesapeake Bay segments in 
the mesohaline salinity zone, not previously classified with deep-water and (or) deep-channel 
designated uses, were evaluated for evidence of stratification and persistent dissolved oxygen 
criteria non-attainment under a range of different Chesapeake Bay water quality/sediment 
transport model loading scenarios. Ten segments meeting these characteristics were identified in 
Maryland and Virginia's Chesapeake Bay tidal waters (Table 11-2). 
Table 11-2. Ten Chesapeake Bay segments in the mesohaline salinity zone of Maryland and 
Virginia’s Chesapeake Bay tidal waters reviewed for possible expanded designated use 
classifications. 
Chesapeake Bay Segment 
Tidal Water Body 
MAGMH 
Magothy River 
SOUMH 
South River 
EBEMH 
East Branch Elizabeth River 
WBEMH 
West Branch Elizabeth River 
CRRMH 
Corrottoman River 
FSBMH 
Fishing Bay 
WICMH 
Wicomico River 
SEVMH 
Severn River 
WSTMH 
West River 
YRKMH 
York River 
Only the South River (SOUMH) and Magothy River (MAGMH) segments met the deep-water 
designated use definition originally described in U.S. EPA 2003 where a measured pycnocline 
was present and presented a barrier to oxygen replenishment during the period June 1 to 
September 30. 
In the South River segment, 39 of 43 depth profiles (91%) had an upper pycnocline and 19 of 43 
depth profiles (44%) had a lower pycnocline. In the Magothy River, 16 of 40 depth profiles 
(40%) had an upper pycnocline and 0 of 40 depth profiles (0%) had a lower pycnocline. 
Evaluation of the Chesapeake Bay water quality/sediment transport model scenario results for 
both segments showed depression of dissolved oxygen concentrations with increasing depth 
suggesting a physical mixing constraint on re-oxygenation due to stratification. 
1 These years of Chesapeake Bay Water Quality Monitoring Program data were selected to be consistent with the 
hydrologic period for management application of the Chesapeake Bay Water Quality/Sediment Transport Model. 
: www.chesapeakebay.net 
12 
