DISTRIBUTION OF WATER. 41 
equable and continuous, has become fitful and uncertain. 
Floods and drouth alternating clearly indicate that the natural 
physical conditions of the region have been unduly disturbed. 
In winter and early spring, when heavy masses of snow have 
been accumulated on treeless precipitous slopes, snow and land 
slides frequently occur with disastrous result to life and prop- 
erty.” 
THE DISTRIBUTION OF WATER. 
The distribution or “run-off” of the water is often a more 
important factor in its economy than the quantity available. 
It is influenced by the surface conditions of the soil cover, by 
the porosity and structure of the soil and by the slope. There 
are two kinds of run-off, the surface run-off and the under- 
ground run-off or percolation. The former is likely to do 
injury by eroding the soil, while the latter is generally beneficial 
to vegetation in the formation of springs and in raising the 
water level in the soil. It is evident that the less surface drain- 
age and the more underground drainage the greater the spring- 
water supply and vice versa. We are, therefore, interested in 
determining the factors that increase underground drainage and 
reduce the surface flow. 
It is plain that whatever retards the flow of water over the 
land aids it in sinking into the soil. We find this exemplified 
in swamps, where the soft, rough ground retards the surface 
flow, and in forests, where the foliage checks the water in its 
descent to the ground and the forest floor retards the surface 
run-off. Theoretically such a cover should promote the flow 
of springs and maintain the height of water in wells, and in 
practice we find that this is often the case. In some cases 
springs had entirely disappeared after the clearing of near-by 
forests, but have commenced their regular flow since the trees 
have been allowed to grow again. Springs in turn influence 
the flow of water in rivers, so that forests about the headwaters 
of streams often have a most potent effect in maintaining their 
flow. There is in fact no influence of the forest that is of 
greater importance in the distribution of water supplies than 
its effect in retarding the run-off, even though its effect in pre- 
venting evaporation is very important. 
