National Geographic : 1911 Feb
THE PANAMA CANAL* BY COLONEL GEORGE W. GOETHALS, CHIEF ENGINEER OF THE PANAMA CANAL IT is not possible in the time at our disposal to enter upon a description of the explorations and investiga tions which were made of various routes proposed for a canal joining the two oceans, nor can an account be taken of the considerations which resulted in the United States finally adopting the Pan ama route. Suffice it to say that under the Spooner Act, approved June 28, 1902, the President of the United States secured the necessary concession from the Republic of Panama, purchased the rights and property of the New French Canal Company, and undertook the con struction of the canal on May 4, 1904. The Isthmus of Panama runs nearly east and west, and the canal traverses it from Colon on the north tc Panama on the south, in a general direction from northwest to southeast, the Pacific termi nus being 22 miles east of the Atlantic entrance. TORRENTIAL FLOODS OF THE CHAGRES RIVER The greatest difficulty of the Panama route is the control or disposition of the Chagres River and its tributaries. The Chagres River rises in the San Bias Mountains and drains a basin of 1,320 square miles, about half of which is above the mouth of the Obispo River. Its course is generally parallel to the Caribbean coast line so far as the mouth of the Obispo, where it turns almost at right angles to the westward, pursuing this general course to Tabernilla, whence it traverses a tortuous channel in a gen eral northwesterly direction and enters the Caribbean Sea to the west of Limon Bay. The general elevation of the valley is but little above sea-level to Bohio, where the low-water surface of the Chagres is one foot above mean tide. At the mouth of the Obispo, 13 miles from Bohio, the low-water surface is 48 feet above, and at Alhajuela, 11 miles farther, it is 95 feet above the same datum. Above Bo hio the Chagres Valley is undulating, the hills becoming higher and steeper as the river is ascended, causing very rapid run-off of the rains, amounting to Ioo inches and over in eight or nine months, the average duration of the wet season. The maximum observed rainfall is 5.86 inches in one hour; the greatest recorded change in the river at Gamboa is a rise of 25.6 feet in 24 hours. Its discharge at the beginning of the rise was 8,200 cubic feet per second, increas ing to 90,ooo cubic feet per second at the peak of the flood. The excessive rain fall and precipitous character of the hills enclosing the valley make it a torrential stream. The bars formed during floods differ materially, and are of sand, gravel, pebbles, and rounded stones three inches to six inches in diameter. The sand and clay deposits are useful in giving suitable material for the impervious portion of the dams, while the gravel beds furnish ballast for the railroad and for other purposes. The Chagres River has 26 tributaries between Bas Obispo and Gatun, the largest of which are the Gatun and Trini dad rivers, the former entering from the east with a drainage basin of about 160 square miles, and the latter from the west, draining an area of about 390 square miles. Each rises in the same character of country as the Chagres, and though with smaller drainage areas, they are of the same torrential character and must be reckoned with in the general question of the control of the Chagres and its tributaries. Various methods for the disposition or control of the Chagres have received consideration. The first French com- * An address to the National Geographic Society, February io, 1911.