262 NIC A RA G UA A ND THE ISTHMIA N RO UTES 



floods of the San Juan, San Carlos, San Francisco, and other 

 streams, no attempt had ever been made to measure their flood 

 discharge or even to make an approximate estimate on this point. 

 It was designed to hold the lake at an elevation of 110 feet 

 above sea-level, any rise above that mark being injurious to prop- 

 ert} r and any fall below reducing the navigable depth of the 

 canal throughout the summit level; yet no attempt whatever 

 had been made to determine the maximum or minimum inflow 

 or the rate of outflow or evaporation from the lake. There was 

 also some discrepancy in the levels and in distances on San Juan 

 river and Lake Nicaragua. 



The Walker commission directed its efforts to supplying these 

 deficiencies and to the investigation of alternate routes with ref- 

 erence to comparative permanence, utilit}% and cost, and also 

 to checking the results of surveys already made. Sufficient in- 

 formation has been obtained to fix plans and quantities within 

 narrow limits, so that disagreements as to cost relate almost en- 

 tirely to the relative efficiency of labor in a warm, wet climate 

 as compared with temperate regions, where we have more data. 



The hydrographic investigations included the measurement 

 of all the principal streams encountered by the possible canal 

 routes, the rainfall all along the line, the evaporation from Lake 

 Nicaragua, and the sediment carried by the San Carlos and Sera- 

 piqui rivers with reference to its influence on the maintenance 

 of the canal. The twelve camps which were established meas- 

 ured twenty streams and took the other observations required. 



On the San Juan one station was maintained at Ochoa, where 

 it is proposed to build the big dam. Another, just above Saba- 

 los, was maintained as being the highest point on the river where 

 a dam might be built and as giving essentially the outflow from 

 the lake, there being no important tributaries between this point 

 and the lake. During the latter part of the dry season a tour 

 around the margin of Lake Nicaragua was made to determine 

 the inflow during the dry season, and, though the preceding 

 rainy season had been the wettest on record, the inflow was 

 found to be practically negligible. Observations show that the 

 average evaporation here in the dry season is about two-tenths 

 of an inch per day. The length of the dry season and the rate 

 of evaporation indicate that in ordinary years the surface of the 

 lake would decline about two feet during the dry season, and 

 this will, of course, decrease the navigable depth of the canal by 



