B-1 
appendix 
Detailed Chesapeake Bay Water 
Quality Criteria Assessment 
Methodology 
The methods in this appendix apply specifically to the evaluation of dissolved 
oxygen criteria. For water clarity criteria or chlorophyll a criteria evaluations, the 
individual methods are very similar to those described here. See chapters 5 and 6, 
respectively, for additional details. Chapter 7 also contains important information in 
using shallow-water data for criteria attainment assessment of all three parameters. 
Data come from the Chesapeake Bay Program's Chesapeake Information Manage¬ 
ment System (CIMS) database or through the CIMS partners’ networked databases. 
The parameters extracted include date, location, depth, salinity, temperature, and the 
water quality parameter under assessment. Data identified by the states, but collected 
from other than the Chesapeake Bay Water Quality Monitoring Program and Chesa¬ 
peake Bay Shallow-water Monitoring Program, are also obtained. These data must 
be of known and documented quality as described in Chapter 3. 
Once the data are compiled, they are assigned to a time period based on the sample 
date. Fixed-station data are normally collected during a monitoring cruise that covers 
the entire tidal Chesapeake Bay over several days. To provide a “snapshot” of water 
quality, however, the data collected within one cruise are considered contempora¬ 
neous to enable a single spatial interpolation. For information not associated with a 
cruise, such as state-supplied data, a cruise number is assigned representing the 
closest cruise in time to the collection of each data point. Co-located data points in 
the same cruise are averaged. 
The criteria assessment procedure requires evaluation over large areas rather than at 
distinct points. Spatial interpolation is carried out for each water quality criteria 
parameter for each cruise (see Appendix D for details on the Chesapeake Bay inter¬ 
polator and the interpolation process) with water clarity and chlorophyll a data 
interpolated in the two horizontal dimensions using inverse distance squared 
weighting and natural logarithm transformation. Dissolved oxygen data are first 
appendix b • Detailed Chesapeake Bay Water Quality Criteria Assessment Methodology 
