C-4 
most of the year, but occur two times a month 
during the summer. At each station, samples are 
collected at multiple depths depending on the 
location of the pycnocline. In addition, techni¬ 
cians collect water quality sensor data— 
including water temperature, salinity, and 
dissolved oxygen—along vertical profiles at 
regular intervals. 
The fixed-station network provides data to assess 
water quality in the mid-channel, open waters of 
the Bay mainstem as well as in the major tidal 
tributaries and embayments. The network does 
not assess conditions in the shallows since many 
of the stations were purposely located in the 
main channels and open tidal waters. 
The Chesapeake Bay Program recently began 
monitoring shallow-water habitats using a tech¬ 
nology known as DataFlow (see Chapter 7 for 
details). This new technology uses a system of 
shipboard water quality probes that measure 
spatial position, water depth, water temperature, 
salinity, dissolved oxygen, turbidity, and fluores¬ 
cence from a flow-through stream of water 
collected near the water surface. This system 
allows rapid data collection (approximately 
every 4 seconds) while the boat is traveling at 
speeds up to 20 knots. Due to the speed of data 
collection, each cruise provides extremely 
detailed data sets useful for assessing highly 
variable water quality conditions, such as those 
expected in the Bay’s shallow waters and small 
tidal tributaries. Thus, this monitoring program 
specifically assesses shallow waters (STAC 
2005). The spatial density of data collected by 
the DataFlow system allows spatial interpolation. 
The current Chesapeake Bay Program interpolation software is not designed for data 
of this density, however, so new methods of interpolation need to be developed. 
Figure C-1. The sites that make up the fixed-station 
network of the Chesapeake Bay Water Quality 
Monitoring Program. 
Source: Chesapeake Bay Program 1989. 
Due to the cost of the Shallow-water Monitoring Program, it cannot be implemented 
baywide concurrently. Rather, the program is being put into practice on a rotating 
basis, with the monitoring system deployed to selected assessment units long enough 
to evaluate attainment and then moved to another set of units (see Chapter 7 for 
further details). This set-up means that all shallow-water areas will not be assessed 
simultaneously, although a full assessment will take place over time. For example, 
the Maryland Department of Natural Resources’ Water Quality Mapping Program 
covered 14 Chesapeake Bay and tributary systems in 2005.These systems include the 
St. Mary’s, Patuxent, West, Rhode, South, Middle, Bush, Gunpowder, Chester, 
appendix c 
Evaluation of Options for Spatial Interpolation 
