44 
ENGINEERING: H. L. ABBOT 
available hydraulic data prior to the date when Gatun Lake began to 
fill, with some later figures added for comparison with those of the second 
table, which includes the entire watershed above Lake Gatun during 
the filling of the lake. In future studies this latter basin will doubtless 
be adopted, as the net outflow is easily determined and rainfall measure- 
ments are now made at many stations. For the second table I first^ 
adopted the mean of the rainfall records at nine stations — Colon, Gatun, 
Trinidad, Camacho, Empire, Culebra, Gamboa, Alhajuela and El 
Vigia — as well representing the average volume falling upon the lake 
watershed near the Canal Zone. Seven new stations then unknown 
to me had been added, and the figures now given are taken from the 
noteworthy paper by Mr. Willson in the Transactions of the Inter- 
national Engineering Congress at San Francisco. 
Hydrology of the Watershed Above Bohio; 779 Square Miles 
PRECIPITATION 
[N THE BASIN ABOVE BOHIO 
GAMBOA FRESHETS 
YEAR 
Colon 
Gamboa 
Rainfall 
Outflow 
Annual 
Dura- 
tion 
AUTHORITY 
Inches 
Inches 
Inches 
No. 
Ft.-sec. 
Inches 
Hours 
1863 
134.3 
120 
Panama Railroad Records 
1864 
123.4 
110 
1865 
107.4 
96 
1866 
129.7 
115 
1867 
120.8 
108 
1868 
120.0 
107 
1869 
114.8 
102 
1870 
149.6 
133 
1871 
99.6 
81 
1872 
168.5 
150 
1873 
87.1 
78 
1874 
137.7 
123 
1875 
94.7 
84 
1876 
124.5 
111 
1877 
115.5 
103 
1878 
86.7 
77 
*187^> 
164.2 
130 
1880 
136.4 
121 
1881 
102.3 
89.5 
100 
de Lesseps French Cie 
1882 
124.1 
79.6 
106 
1883 
115.3 
76.6 
100 
21 
201 
1884 
86.5 
95.9 
95 
25 
334 
*1885 
146.3 
97.5 
127 
37 
437 
1886 
137.2 
102.9 
125 
43 
437 
1887 
154.9 
136.2 
151 
46 
709 
*1888 
102.6 
127 
29 
596 
* Great flood of the Chagres River. 
