From the outset the French engineers commenced collecting data relating to the hydrology of the Isthmus, and when funds grew low, and the proposed level of the canal began to rise, the matter received ever-increasing attention.
"The Panama Canal and its Makers"
Vaughan Cornish
This is evidenced by the inclusion of geologic discussions in most textbooks of hydrology, and in the reports of the Hydrographic Branch of the U.S. Geological Survey.
"The Economic Aspect of Geology"
C. K. Leith
But the special condition of the woodlands, as affected by snow and frost in the winter of excessive climates, like that of the United States, has not been so much studied as it deserves; and as it has a most important bearing on the superficial hydrology of the earth, I shall make some observations upon it before I proceed to the direct discussion of the influence of the forest on the flow of springs.
"The Earth as Modified by Human Action"
George P. Marsh