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Recap Comparing Results of Various Bottom Studies
Source: Official bottom studies test results with Excel spreadsheet calculations
SUMMARY
Compared Data from Lake Okabena Bottom Studies
Over a series of Years
Note: The tests were done in different places from year-to-year
             
    1999 1977 1963 1956 1952 1944  
 BASIC INFORMATION              
# test spots of core borings done 219 180 n/a 48 7 58  
Dam Run over level (elevation above sea level) 1576 1576 1576 1576 1576 1576  
Level of water at time of study 1576.2 ? n/a 1573.2 1576.09 1575.2  
               
 WATER DEPTH              
Maximum depth of Water at spots tested 15.1 13 n/a 9.1 6.9 11.7  
Elevation at bottom water at deepest spot 1560.9 1563 n/a 1566.9 1569.1 1564.3  
Average Water Depth over all points in each study1 7.4 7.5   6.6 6 6.4  
Std Deviation 2.21 1.1   0.49 0.94 1.91  
               
 SILT DEPTH              
Maximum Silt depth at spots tested 12.4 12 n/a 13.5 14.5 7.6  
Average Silt Depth at spots tested1 4.22 3.3 n/a 6.3 6.7 4.4  
Std Deviation 2.96 1.5 n/a 3.31 3.62 1.94  
# places where there is more Silt then Water 28 2 n/a 36 2 19  
% Average Silt to Average Water depth1 57.0% 44.0%   95.49% 110.24% 69.09%  
               
 WHERE IS HARD BOTTOM              
Maximum water depth at this point w/o sand or silt 23.8 20 n/a several 20.9 several  
Elevation of lowest point where Hard Bottom began 1552.2 1556 n/a see data 1555.1 see data  
Which test site was this #99 Row 2-7 n/a see data #11 see data  
             
To see the Bottom Study details click a link  ==> 1999 1977 1963 1956 1952 1944  
1Editors Note: Please be aware that the calculated averages, though valid for each year, are not totally comparable from one years study to the averages of another years study. This is due to several factors that effect the calculation of averages 1) The differences in what area of the lake was tested ( deep or shallow), 2) the number of tests done. The difference in the averages may be more of a reflection of the methods used than they are a reflection on how either water depth or silt depth has changed.

1999 Lake Study Overview
Sample 1999
test result
January 1999

There were more places tested in this study than in any of the other lake studies.

This was the first study done after dredging was stopped in 1983.

Most of the testing was done in 6 north-to-south cross sections of the lake and around the four (4) man-made, deep areas.

The data from this study produced the Depth Chart for Lake Okabena that is in use.

The physical effort was done by the members of the Fishing Club working with Zielstra Surveying, Windom, MN under the guidance of the Soil Conservation office. Engineering materials and drawings from this data were done by Houston Engineering, Fargo, ND

The method of testing used was a simple stick test which senses the boundary of water/silt and hard bottom.

The data has been keyed to an Excel spreadsheet, images have been made of each test and presentations have been made to view the data from different perspectives

1977 Lake Study Overview
There were two bottom studies done in 1977
  1. A simple stick test at 180 places on the lake to determine water and silt depth. This study followed a grid pattern of rows and columns covering the whole lake. This study rounded off the results to an even Foot
  2. a Core Boring study of 6 selected places to a depth of 26 feet showing the various layers of material and their thickness at that test point. This study rounded off the results to the Tenth of a Foot.

1963 Lake Study Overview
January 1963
No data has been found from this study.  A lake map noting where the tests were done exists. This study was probably done to assist the next series of dredging efforts.

1956 Lake Study Overview
Sample 1956 test result
January 1956
 
This was a core boring style of bottom study. Each test result shows the actual composition of the bottom at each point tested. The results of this study were recorded on the same lake map drawing as the 1952 results.

The lake was low at the time of the study, being 2.8 feet below dam runover level.

The data has been keyed to an Excel spreadsheet, images have been made of each test result using colors to designate each layer of material such as silt, sand, clay, etc. Presentations have been made to view the data from different perspectives

  • Water Depth sequence        ( test result images placed left-to-right in Water depth sequence )
  • Silt Depth sequence             ( test result images placed left-to-right in Silt depth sequence )
  • Tests in number sequence   ( test result images placed left-to-right in test number sequence )
  • Lake Inter-active Map



1952 Lake Study Overview
Sample 1952 test result
January 1952
 
This was a core boring style of bottom study. Each test result shows the actual composition of the bottom at each point tested. The results ot this study were recorded on the same lake map drawing as the 1956 results.

Seven of the original fourteen test results from 1952 were not able to be read and are not part of this presentation.

The data has been keyed to an Excel spreadsheet, images have been made of each test result using colors to designate each layer of material such as silt, sand, clay, etc. Presentations have been made to view the data from different perspectives

  • Water Depth sequence         ( test result images placed left-to-right in Water depth sequence )
  • Silt Depth sequence              ( test result images placed left-to-right in Silt depth sequence )
  • Tests in number sequence   ( test result images placed left-to-right in test number sequence )
  • Lake Inter-active Map

 

1944 Lake Study Overview
Sample 1944
test result
January 1944

This was a core boring style of bottom study. The results show the actual composition of the bottom at each point tested. Unfortunately, there is no way to know where these tests were done. There is no lake map with this study.

The data has been keyed to an Excel spreadsheet, images have been made of each test result using colors to designate each layer of material such as silt, sand, clay, etc. Presentations have been made to view the data from different perspectives

  • Water Depth sequence        ( test result images placed left-to-right in Water depth sequence )
  • Silt Depth sequence             ( test result images placed left-to-right in Silt depth sequence )
  • Tests in number sequence   ( test result images placed left-to-right in test number sequence )

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