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^[[SP-A-1  Dr Coolidge]]

^[[copies to: HBuechner
FRFosberg
LMTalbot]]

Dr. Kang Yung Sun
Professor of Zoology, Seoul National University, Seoul, Korea.

Dear Dr. Kang:

The following are some ideas for Geo-Hydrological studies that might be incorporated into the Ecological Studies of the DMZ, currently being started by your group at the University.  This follows our two meetings at the University during the past two months.  A study of the geology and hydrology of the sites will make give more meaning to the zoological and botanical studies being made because the life processes can be related to the water supplies on which they depend.  In addition, the study of the hydrologic conditions in the DMZ will give the Korean government an area for comparison.  This is the only part of Korea that is not being disturbed by man.

Following are items that you may wish to discuss with Dr. Coolidge of the U. S. National Academy of Sciences when you visit him in May:

Maps of the geology and soils are needed to relate plant life to any zoning conditions found ;

The depth to water in the ground should be determined, springs mapped and measured, and the chemical quality of the water determined;

Precipitation should be measured on some convenient pattern, depending on the size of the area and the topographic conditions;

Surface water runoff should be measured.  This can be done by the use of a staff gage and readings being taken at predetermined time intervals, or by the installation of a continuous recorder.

The amount and character of the sediment being carried by the stream should be determined.  If vegetation has grown to the extent that the rivers no longer carry sediment, this is significant and should be noted. This will be important information to those now contemplating the construction of reservoirs.

To make this study even more meaningful, it would be desirable to chose an area within the Republic that is outside the DMZ and immediately adjacent to the areas now under study, and make the same studies for comparative data.  In the years to come you would then be able to point out the advantages or disadvantages of reforestation to water yield and sediment yield of a basin.

Please extend my regards to Dr. Coolidge when you go to the States.

Sincerely yours,

^[[signed]] JT Callahan]]
28/4/66 [[/signed]]

^[[PACIFIC SCI BD
NAS 
2101 Const Ave NW
WASH 20418]]