Analysis of three years of complete-field temperature data from different sites of heated surface discharges into Lake Michigan Page: 7 of 58
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The 1973 data-gathering system was improved over the 1972 system only
in the use of faster response YSI Series 700 linearized thermistors for tem-
perature measurements. These thermistors were specially made with 0.6-s
The system for data acquisition was somewhat less sophisticated in field
year 1971. The major difference was that data were taken only in paths be-
tween numbered buoys located in the plume. The recording technique used in-
volved manually switching from one probe to another, and transcribing by
hand the temperature displayed on the digital thermometer. A constant speed
was maintained by the boat between buoys, and a constant time interval be-
tween interrogations of each probe was assumed. A second-generation plume-
measuring system, which eliminated the manual interrogation and recording of
temperature information, was used from August 16, 1971 until the end of the
1971 field year. Ambient current measurements were made in that year using
an Ekman-Merz current meter; as with the Bendix Q-15, it has an impeller
with a directional vane which orients the impeller. Meteorological measure-
ments were taken solely on the boat; wind measurements were made using a
Weather-Measure Three-Cup anemometer with direction vane and a meter read-
out. Consequently, the 1971 data were not as refined as for the field year
1972. References 6-8 describe the data collection and instrumentation as
well as the individual plumes themselves in more detail.
The isotherm maps drawn from the plots of the boat measurements were
then analyzed for plume characteristics: centerline trajectories, centerline
temperature decays, temperature half-widths, surface isotherm areas, and
temperature half-depths along the centerline. These characteristics will
vary with current magnitude and direction, wind speed and direction, ambient
lake turbulence, and surface heat loss, as perhaps the most important para-
meters. Most plumes from the same site were found to have similar excess
temperatures and discharge flow rates; this is no surprise since they are
all base-loaded plants. Consequently the flow rate and excess temperature
variation were not considered as important in determining plume character-
istics as were the environmental conditions.
Tables III, IV, and V summarize the data acquired at the above four
sites during the 1971, 1972, and 1973 field years. The large amounts of
data taken at the Point Beach and Palisades sites were required for an un-
derstanding of the different types of plumes possible at the given site as
ambient conditions vary. It was possible to classify the plumes measured at
Point Beach and Palisades into five categories. These categories are listed
in Tables III and IV and specified by the variation in ambient current and
wind at these sites. Figure 5 illustrates the wide range in excess-tempera-
ture ratios measured along the plume centerline at the Palisades and Point
Beach sites as ambient conditions changed from plume to plume. The letters
in this figure refer to specific plumes listed in Tables III and IV. The
division of data into like environmental conditions as done in Tables III-V
thus becomes advantageous. (It should be kept in mind that additional data
at these sites might indicate some new categories.) The sets of plume data
presented in Tables III-IV were analyzed each within its own category, and
finally the averaged characteristics were inter-compared. The results are
3. DISCUSSION OF PALISADES PLUMES
The Palisades data are plotted in Figs. 6-17, grouped according to en-
vironmental conditions. This was found to be the most productive approach
in attempting to explain physically the variations found in the data. It
thereby aided in understanding the causes of the large scatter (see Fig. 5)
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Kyser, J.M.; Paddock, R.A. & Policastro, A.J. Analysis of three years of complete-field temperature data from different sites of heated surface discharges into Lake Michigan, article, January 1, 1974; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1023368/m1/7/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.