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Mckeon, J. B.

Rogers, R. H.

English

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use made thereof'" WATER QUALITY MAP OF SAGINAW BAY FROM 
COMPUTER PROCESSING OF LANDSAT-2 DATA
 
John B.McKeon and Robert H. Rogers
 
Bendix Aerospace Systems Division
 
3621 South State Road
 
Anrn Arbor, Michigan 48107
 
August 1976
 
Special Report
 
Origtl phoegraphy may be purchased from 
EROS Data Center 
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Prepared for:
 
GODDARD SPACE FLIGHT CENTER 
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COLOR ILLUSTRATIONS­
(E76-10477) WATER QUALITY MAP OF SAGINAW N76-31624
 
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TECHNICAL REPORT STANDARD TITLE PAGE 
1.Report No. 2. Goyernment Accession No. 3. Recipient's Catalog No. 
4. Title and Subtitle 5. Report Date 
Water Quality Map of Saginaw Bay from 
Computer Processing of LANDSAT-2 Data 
August 1976 
6.Performing Organization Code 
7. Author(s) 
J.B. McKeon and R.H. Ro B. Performing Organization Report No. BSR 4241 
9. Performing Organization Name and Address 10. Work Unit No. 
Bendix Aerospace Systems Division 11. Contract or Grant No. 
3621 South State Road NAS5-20942 
Ann Arbor, Michigan 48107 13. Type of Report and Period C...ed 
12. Sponsoring Agency Name and Address 
Goddard Space Flight Center Special Report 
Greenbelt, Md 20771 4.Sponsoring Agency Code 
15. Supplementary Notes 
16. Abstract 
Chemical and biological water quality data collected July 31, 1975


at 16 stations within Saginaw Bay, Michigan, in concert with a


LANDSAT overflight, have been processed to enable prediction of


water quality in non-sampled areas. Measurements included: tempera­

ture, secchi depth, chloride, conductivity, total kjeldahl nitrogen,


total phosphorous; chlorophyll a, total solids and suspended solids.


When these nine water quality parameters'were treated as dependent

variables and LANDSAT measurements as independent variables, and


processed by linear regression analysis, all parameters had correla­

tion coefficients greater than that for the 99% level of significance.


The regression equations were used to produce a five color map show­

ing the distribution and concentration of the nine water quality


parameters over the entire bay.


17. Key Words (S Tected by Author(s)) 18. Distribution Statement 
Water Quality, Computer Processing,


Lake Eutrophication, LANDSAT,


Multispectral Data, Satellite


Monitoring


19. Security Clossif. (of this report) 120. Security Classif. (of this page) 21. No. of Pages 22. Price­
Introduction


Since June of 1974 the Bendix Aerospace Systems Division has been


conducting an extensive research program in the surveillance of lake eutro­

phication from LANDSAT. To accomplish this goal, LANDSAT data products are


being generated to support the Environmental Protection Agency (EPA) modeling


study of lake eutrophication in Saginaw Bay; the State of Michigan's survey


of inland lakes and watersheds for the purpose of assessing the effects of


watershed land use on lake water quality; and the State of Wisconsin's lake


survey to determine eutrophication status, causes, effects, and control treat­

ments. This report addresses the development of one specific map of Saginaw


Bay.


a The EPA sponsored study of water quality in Saginaw Bay (Lake Huron)


aims to describe, on a seasonal basis, the circulation and water masses in


the Bay; to monitor inputs of nutrients from its watershed; and to develop


and evaluate models for predicting water quality in the Bay as a function of


various control strategies (Ref. 1). A surface/subsurface measurement pro­

gram, under the direction of Dr. V. Elliott Smith of the Cranbrook Institute


of Science and EPA, has been underway since .April 1974. From each of 61


stations distributed throughout Saginaw Bay, some 30 water quality parameters


are determined on an 18-day cycle that coincides with the LANDSAT overflights.
 

Technique


A varietyof analytical approaches have been applied to relate water


quality data from Saginaw Bay to LANDSAT data (Ref. 2,3, and 4). These


approaches included multiple stepwise linear regression with both ratios of


band means and single band means. The procedure reported here was determined


to be the most efficient and productive of the approaches investigated.


LANDSAT-2 computer compatible tapes for two consecutive scenes, acquired


on 31 July 1975 (2190-15401 and 2190-15404), were processed on a Bendix MDAS


(Multispectral Data Analysis System). The satellite data was first geo­

metrically controlled by using ground control points, coastal features digitized


from navigation charts. Each water quality station was called up and located­

on the color TV monitor. A cursor was shaped around each of the 16 stations


(those sampled the same day as the LANDSAT overpass) so as to include an


average of 80 pixels per station area. The mean reflectance, in raw data


counts, was extracted as the independent variables and applied to a linear


regression program with nine water quality parameter surface measurements


(Ref. 5). (Earlier studies had indicated data from bands 4 and 5 provide


the best correlation coefficients, while those from bands 6 and 7 do not contri­

bute significantly to the regression.) The resulting regression equations
 

(maximum count in bands is 254) are:


1


Regression Equations


Saginaw Bay 7/31/75 (16 Samples)


Temperature (oc) = 9.61 + 0.007 (Band 4) + 0.572 (Band 5)


Secchi Depth (m) = 8.24 + 0.142 (Band 4) - 0.458 (Band 5)


Chloride (mg/i) = 9.489 - 2.040 (Band 4) + 3.202 (Band 5)


Conductivity (micromhos) = 194.1 - 7.72 (Band 4) + 13.79 (Band 5)


Total Kjeldahl Nitrogen (mg/i) = 0.419 - 0.102 (Band 4) + 0.153 (Band 5)


Total Phosphorus (mg/i) = -0.0069 - 0.0033 (Band 4) + 0.0059 (Band 5)


Chlorophyll - (ug/l) = 0.908 - 1.02 (Band 4) + 1.67 (Band 5)


Total Solids (mg/i) = 154.1 - 7.73 (Band 4) + 12.93 (Band 5)


Suspended Solids (mg/l) = 41.04 - 8.32 (Band 4) + 11.57 (Band 5)


The correlation coefficients ranged from .73 for Secchi Depth to .94 for


Temperature, Nitrogen, and.Phosphorus. In all nine cases the level of


significance was at P(.001.


Next, the unprocessed LANDSAT data was again displayed on the color TV


monitor. The entire bay was carefully screened in a false color mode and also


in level slice modes of bands 4 and 5. This effort enabled the investigator


to identify five distinct water masses. After the cursor was positioned to


representative areas of each mass, training areas, the mean reflectance and


desired colors were entered into MDAS's multivariate categorical processor.


The entire bay and part of east-central Michigan was categorized, the two


scenes were "end-to-end" merged, and finally the processed data was filmed


as three color separates on a drum recorder.


In order to relate the color coded map of the bay to levels of water


quality the means of each of the five water masses were entered into the


equations given above. The mean counts of the training areas in bands 4 and


5 respectively were; blue 30.3 and 18.9, green 36.7 and 23.5, orange 41.6


and 26.8, red 42.7 and 30.4, and magenta 45.6 and 37.8. The final color pro­

duct is shown as the attached figure at the original filming scale of


1:1,000,000.


Discussion


Evaluation of the water quality map is not completed but some interest­

ing features have already been identified.


The Saginaw River enters Saginaw Bay at its extreme southwestern end and


contributes the majority of pollutants found in the Bay. The river and its


tributaries drain an area of more than 16,060 km2 that is predominantly agri­

cultural land and contains four major urban centers. The magenta color, which


2


represents levels of water quality that are beyond the range of the sample
 

data used in the regression program, enhances the plume of turbid water that


enters the Bay.from the Saginaw River and extends in a southeast direction.


In the shallow near-shore zone (less than six feet deep) of the lower bay,


the magneta denotes areas where there is significant local resuspension-of


sediment.


A lobe of relatively clean -Lake Huron water (blue) appears to enter


the mouth of the Bay between a central island (Charity Is.) and a coastal


point (Lookout Pt) and flow up the Bay (south) along its deepest channel.


The boundary of thelobe and the Bay water (green) is very pronounced and


not gradational as is the case with the remaining three water mass boundaries.


A third feature is the spiral of water masses just northeast of the


"thumb" of-Michigan. This is an apparent mixing zone of turbid water that


has been transported from the Bay into Lake Huron. The transporting current


may have been set up bythe counterclockwise deflection of southward moving


Lake Huron water, along the shallow .area between Charity Island and the


eastern shore of the Bay mouth (Oak Pt.). Thus one mass of Lake Huron water
 

enters the Bay along its western shore while another mass isprevented from


entering but helps transport turbid bay water into Lake Huron. The apparent


increase in turbidity at the top right corner of the map is due to the pre­

sence of an atmospheric haze associated with clouds, about 25 km northeast


of the right corner of the map, but within the full scene.


The nine water quality parameters were mapped as one map. If separate


maps were required for each parameter the breaks between color levels could


be relocated so as to better proportion the levels. For example, the map


shown here. indicates that chlorophyll d is low in the outer bay and central


portion of the inner bay but extremely high in the near shore zone of the


inner bay. A separate map, made with different training areas, could be


made for each parameter. In the case of chlorophyll d this would permit


perhaps one color code for the areas of low concentration and four colors


for the areas of high concentration as opposed to three and two respectively.


Itshould be emphasized that the equations used to relate the water


quality measurements with the LANDSAT data are not necessarily applicable


to LANDSAT data of a different date. Atmospheric conditions can be extre­

mely variable with time over-the Bay region.
 

Conclusion


Computer processing of LANDSAT digital data and water quality surface


truth measurements taken on the day of the overpass provides a means of pro­

ducing a synoptic map of Saginaw Bay water quality for non-sampled areas. Use


of non-linear regression and work with data of different dates may help to


further the goals of the EPA in their effort to study the circulation of water


masses and model the water quality of Saginaw Bay.


3 
References


1. 	 P.L. Freedman; "Saginaw Bay; An Evaluation of Existing and-Historical


Conditions:; EPA Report 905/9-74-003; April 1974.


2. 	 R.. Rogers, L.E. Redd, and V.E. Smith; "Computer Mapping of Turbidity


and Circulation Patterns in Saginaw Bay, Michigan (Lake Huron) from


ERTS Data"; Presented at ASP-ACSM Convention, 9-14 March 1975; NASA-CR­

142923; NTIS Order Number E75-10321.


3. 	 R.H. Rogers, N.J. Shah, J.B. McKeon,-C. Wilson, L. Reed, V.E. Smith,


and N.A. Thomas; "Application of LANDSAT to the Surveillance and Control
 

of Eutrophication in Saginaw Bay"; Tenth International Symposium on


Remote Sensing of Environment, 6-10 Oct 1975 (inpress).


4. 	 R.H. Rogers, N.J. Shah, J.B. McKeon, and V.E. Smith; "Computer Mapping


of Water Quality in Saginaw Bay with LANDSAT Digital: Data"; Proceedings


of ACSM-ASP Convention, Washington, D.C., 22-28 February 1976.


5. 	 M.A. Efroymson; "Multiple Regression Analysis"; in A. Ralston and


H.S. Wilf (eds.) Mathematical Methods for Digital Computers; John Wiley;


pp. 191-203; 1960.


4


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Water quality map of Saginaw Bay from computer processing of LANDSAT-2 data

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