552 THE PANAMA ROUTE FOR A SHIP CANAL. 



purpo.ses oi the canal and for wastag-e by evaporation through the 

 lowest rainfall seasoi. The floods of the Chag-res, therefore, instead 

 of constituting the obstacle to construction and convenient mainte- 

 nance of the canal heretofore supposed, are deprived of all their 

 prejudical effects and transfornKnl into beneficial agents for the opera- 

 tion of the waterwa}". 



The highest floods are of short duration, and it can be stated as a 

 general law that the higher the flood the shorter its duration. The 

 great floods which it is necessary to consider in connection with the 

 maintenance and operation of this canal would last but a comparatively^ 

 few hours only. The great flood flow of 140,000 cul)ic feet per second 

 would increase the current in the narrowest part of the canal below 

 Obispo to possibly 5 feet per second for a few hours only, but that is 

 the only inconvenience which would result from such a flood discharge. 

 That velocity could be reduced l^y additional excavation. 



Inasmuch as this system of control, devised and adopted by the 

 Isthmian Canal Commission, is completely effective in regulating the 

 Chagres floods, the reservoir proposed to be constructed by the new 

 Panama Canal Company at Alhajuela, on the Chagres about 11 miles 

 above Obispo, is not required, and the cost of its construction would 

 be avoided. It could, however, as a project, be held in reserve. If 

 the traflic of the canal should increase to such an extent that more 

 water would be needed for feeding the summit level, the dam could 

 be built at Alhajuela so as to impound enough additional water to 

 acconnnodate, with that stored in Lake Bohio, at least five times the 

 10,000,000 annual traflic already considered. Its existence would at 

 the same time act with substantial effect in controlling the Chagres 

 floods and relieve the Gigante spillwaj^ of a corresponding amount of 

 duty. 



The locks on the Panama route are designed to have '•■ " * a 

 usable length of 740 feet and a clear width of S-t feet. They would be 

 ])uilt chiefly of concrete masonry, while the gates would be of steel 

 and of the miter type. 



The great dam at Rohio raises the water surface in the canal from 

 sea le\el in th(> Atlantic maritime soetion to an oi'dinaiy maxinuim of 

 90 feet above sea level; in otluM- words, the maxinuun ordinary total 

 lift would be 1)0 feet. This total lift is divided into two ])arts of 45 

 fe(4 cacli. There is th(M'(^foi-e a flight of two locks at IJoliio; indeed, 

 there are two flights side b>^ side, as the twin a^rrangement is designed 

 to be used at all lock sites on both routes. The typical dimensions 

 and arrangements of these locks, with the re()uisite culverts :uul other 

 features, * ■" " are not essentially different from other great mod- 

 ern ship-canal locks. The excavation for the Bohio locks is made in 

 a rocky hill against which the southwesterly end of the proposed 

 Bohio dam rests, and tliev are less than 1,000 feet from it. 



