CHAPARRAL. 7 
because they are not inflammable or because they will quickly make a 
new growth from the roots after they have been burned. 
On the whole, it is doubtful if chaparral can be credited with being 
a good protector of snowfall. Its office as a cover is to conserve the 
rains, which constitute by far the greater portion of the precipita- 
tion. Ii is only in the highest zones that heavy snows occur, and the 
phenomenon has been observed only once near the level of the sea. 
That was in the northern portion of the chaparral region, at San 
Luis Obispo, in 1896. 
Mr. L. C. Miller, of the Forest Service, in summing up the results 
of a detailed investigation of the effects of chaparral cover on water- 
sheds and along streams near Los Angeles, and of a general study in 
other localities, stated: 
The density and character of the cover is extremely important. Both of these 
factors have an influence on the water supply of every stream in southern Cali- 
fornia. The trees and shrubs which form the stream cover are important in 
retarding evaporation and thus preventing a decrease in the water supply. 
The vegetation which forms the cover for the mountain slopes is of still greater 
importance. 
The assertion is sometimes made that trees hold off from the ground 
8 per cent of the falling rain, which is soon evaporated; and, further, 
that they take out of the ground an additional 25 per cent, which is 
either converted into vegetable structure or transpires in vapor. The 
inference sought to be drawn is that because of the plants there is 
less water available for use. The case, however, may be presented in 
another way. In a region with an annual rainfall of 15 inches and 
an annual evaporation of 60 inches, where the stream beds are entirely 
dry, except after heavy downpours, and where no flow of water ex- 
tends far enough down a valley to reach a reservoir or irrigation ditch, 
conditions could hardly be worse. Such conditions do in fact exist. 
For seven years there was no flow into the Sweetwater Reservoir, 
near San Diego. Only a small portion of its watershed was forested, 
and the chaparral, from repeated burning and overgrazing, made but. 
a poor cover. It is true, of course, that if the watersheds had been 
covered with chaparral or forests the trees would have taken all the 
rainfall necessary for their sustenance, and this water would certainly 
never have reached the reservoir. Without trees, however, the mea- 
ger precipitation and excessive evaporation kept the reservoir dry. 
If the evaporation, which is least during the rainy season, could have 
been sufficiently reduced by a proper tree cover, the streams would 
have begun to flow. The owners of the reservoir could well have. 
afforded to let the sun take 50 per cent of the water and the trees 25 
per cent more, if they could have been sure of getting the remaining 
25 per cent. That would have been better than getting no water 
at all. : 
O1565e—_ Bulls 3 
