A-18 
temperature, salinity, dissolved oxygen, turbidity (clarity of the water), and chloro¬ 
phyll (indicator of plankton concentrations) from a flow-through stream of water 
collected near the water body’s surface. This system allows data to be collected 
rapidly (approximately every 4 seconds) and while the boat is traveling at speeds up 
to 20 knots. 
In 2005, the MDDNR Water Quality Mapping Program covered 16 Chesapeake Bay, 
Coastal Bay and Tributary systems. The St. Mary’s, Patuxent, West, Rhode, South, 
Middle, Bush, Gunpowder, Chester, Eastern Bay, Miles/Wye, Little Choptank, 
Chicamacomico and Transquaking Rivers will be mapped, as well as Fishing Bay 
and the Maryland Coastal Bays. In Virginia, dataflow data are available for the 
Piankatank, York, Pamunkey and Mataponi Rivers. 
Beginning in 1990, Chlorophyll-a concentrations were measured over the mainstem 
Chesapeake using aircraft remote sensing. From 1990-1995, the instrument used for 
this study was the Ocean Data Acquisition System (ODAS) which had three 
radiometers measuring water leaving radiance at 460, 490 and 520 nm. In 1996, an 
additional instrument was added, the SeaWiFS Aircraft Simulator (SAS II). SAS II 
has sensors at seen wavebands which improves detection of Chlorophyll in highly 
turbid areas. Since 1990, 25-30 flights per year have been made during the most 
productive times of year. 
The data described above and additional information can be obtained from: 
www.chesapekebay.netmddnr.chesapeakebay.net/eyesonthebay/index.cfm 
www2.vims.edu/vecos/ 
Description of the Current Nearest Neighbor/IDW Interpolator 
The current Chesapeake Bay Interpolator is a cell-based interpolator. Water quality 
predictions for each cell location are computed by averaging the nearest “n” neigh¬ 
boring water quality measurements, where “n” is normally 4, but this number is 
adjustable. Each neighbor included in the average is weighted by the inverse of the 
square of Euclidean distance to the prediction cell (IDW). Cell size in the Chesa¬ 
peake Bay was chosen to be 1km (east- west) x 1km (north-south) x 1m (vertical), 
with columns of cells extending from surface to the bottom of the water column, thus 
representing the 3-dimensional volume as a group of equal sized cells extending 
throughout the volume. The tributaries are represented by various sized cells 
depending on the geometry of the tributary, since the narrow upstream portions of 
the rivers require smaller cells to accurately model the river’s dimensions. This 
configuration results in a total of 51,839 cells by depth for the mainstem Chesapeake 
Bay (segments CB1TF-CB8PH), and a total of 238,669 cells by depth for all 77 
segments which comprise the mainstem Bay and tidal tributaries. 
The Chesapeake Bay Interpolator is unique in the way it computes values in 3 
dimensions. The interpolator code is optimized to compute concentration values, 
which closely reflect the physics of stratified water bodies, such as Chesapeake Bay. 
The Bay is very shallow compared to its width or length; hence water quality varies 
much more vertically than horizontally. The Chesapeake Bay Interpolator uses a 
vertical filter to select the vertical range of data that are used in each calculation. For 
appendix a 
The Cumulative Frequency Diagram Method for Determining Water Quality Attainment 
