12 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
same fall that they are not characterized by the long- stretches of low, meandering 
grade found near the coast in the play as to the north. They emerge, on the con- 
trary, from the mountains at but 4 to 5 miles from shore line at altitudes of 200 to 
400 feet, and as a result this elevation is passed with comparatively steep slopes over 
rocky or bowlder-strewn channels. Above these coastal stretches and within the 
mountains the lengths of the rivers are so short for the relatively great heights which 
they fall that their dimensions are little greater than those of the smallest brooks 
which How from the hill summits in the Rocky Mountains. 
The rivers of the north and of the west are more like the streams of humid 
regions in the United States, as their perennial discharge is always fairly well main- 
tained. The larger of these rivers have at low-water stage bed-widths of 150 to 200 
feet, average depths of 2 to 4 feet, and minimum discharges of 250 to 1,500 second-feet. 
In time of flood, although these rivers attain maximum discharges of 10,000 to 20,000 
second-feet, these volumes are not greatly in excess of the flood discharges of the 
rivers of the southern slopes. 
The width of stream-beds of the southern rivers is often as great as that of those 
entering the northern coast, but owing to the infrequency and small amount of the 
precipitation and the relatively porous character of the soil, reducing the percentage 
of run-off, as well as to the smallness of their catchment basins, they discharge 
minimum volumes of but 50 to 100 second-feet. These streams resemble the rivers 
of our Western plains in that their beds are nearly dry the larger part of the year, but 
they are yet of sufficient capacity to discharge great volumes during the sudden 
floods to which they are subject. The beds of these rivers, even near the coast, are 
bowlder-strewn and from 100 to 300 feet in width. The depth of their banks is 10 to 
20 feet, yet the minimum surface-width of such streams is but 50 to 100 feet and their 
average depth 0.5 to 1.5 feet during their minimum discharge. In maximum flood 
such streams reach discharges aggregating 5,000 to 10,000 second-feet, in some cases 
even more, as shown by their wide, rocky, dry beds. 
Though the number of streams and branches which have received names is said 
to be over 1,200, the number named on the best maps does not exceed 100. On one 
map 81 streams have received separate names; of these, 43 flow directly into the ocean, 
while the remaining 38 are tributary to them. Probably not over 50 of the entire 
number would be called rivers in the United States. 
In the mountains the water in most of the streams is usually exceedingly clear, 
but in the lower portions it is often muddy, although the streams examined by us in 
January and February were, as a rule, quite clear. 
Our opportunities enabled us to examine only a few of the streams and only in 
the most general way. The following brief descriptions of some of the principal 
ones examined are based partly upon our own observations and partly upon those of 
Mr. H. M. Wilson. 
Rio Loiza . — This is perhaps the longest river on the island. It has its source well 
toward the south where the divide is near the southern coast, northeast of Guayama, 
flows near the towns of San Lorenzo, Caguas, and Carolina, and enters the ocean about 
15 miles east of San Juan. At Carolina it is a broad, shallow stream, with sand and 
gravel bottom and moderately clear water, and when seen by us (February 20) the 
ford near there was perfectly safe for carriages, the water probably not exceeding 
2.5 feet in depth. Mr. Wilson gaged this river near Carolina in January and reports 
