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Underground Water as a Factor in Geological Processes E. Sherbon Hills 
Ankora Symposium in Arid Zone Hydrology UNESCO 
New York, 1953 
Most of the descriptions of Old World savannas are taken from: 
Climatic Accidents in Landscape -Making C. A. Cotton 
Whitcombe & Tombs Ltd. Cristchurch, 
N.Z., 1947 
American geologists' thinking on the temperate semiarid regions of North 
America is summarized by Fenneman. 
Physiography of Western United States Nevin M. Fenneman 
McGraw -Hill Book Co. New York, 1931 
With approximately the same rainfall, stream flow in Norway and south- 
em Japan is distinct. Part of this is undoubtedly due to frozen winters, 
but a good part is also due to greater runoff and shallow ground -water 
depths in Norway. 
Where topography results from underground drainage, stream piracy is of 
frequent occurrence. Noteworthy examples are: 
a. Oronoco River and Rio Negro (Amazon tributary) via Casiquiare 
Canal (a natural waterway). 
b. Rio Bonue (Niger River tributary) and Logone River which flows 
into Lake Chad. Fresh Lake Chad waters are also being pirated 
by underground waters, probably into the Sahara. 
c. Near the bend of the Niger River east of Tombouctou (Timbuktu) 
piracy has occurred by the Niger River just prior to the time of 
African colonial history. 
d. On the southern Mexico plateau Rio Balsas and Rio Verde, flow- 
ing into the Pacific are pirating streams flowing into the plateau 
basins. The piracy is by stream channels (due to regional up- 
lift) but where such stream beds are 200 meters deep and "so 
narrow a man can jump across," the cause is groundwater 
drainage. 
The quote is from an article by Rita Lopez de Llergo in the 
Ankara Symposium on Arid Zone Hydrology. UNESCO, New York, 
1953. 
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