FOREST AREAS AND SOIL WATER 
147 
of supply — to the waste of storm waters through floods in lieu 
of compelling them to pass into the soil and enter the normal 
circulatory system through which alone the waters of the earth 
can be fully utilized. Thus, McGee concludes that so far as may 
be estimated, at least 80 or 90 per cent of the lowering recorded 
in 31 typical states is due not to excessive removal of water from 
the subsoil, but to failure to get a normal supply into the soil and 
on into the subsoil beneath. 
Now, Zon shows clearly that the effect of forest growth on 
soil water, in the immediate area of the forest at least, and in a 
level country with a minimum of run-off differs greatly from that 
in a mountainous or hilly country with maximum run-off. That 
is to say, in the former forests tend to act as drainers of the soil 
moisture and hence would apparently tend to lower the water 
table in their immediate vicinity. In the latter, because of the 
interception of run off, they have the opposite effect, namely, 
that of increasing the water content and of prolonging the period 
during which the water of the soil is depleted. He states further 
that observations carried on in forests over broken topography, 
where the geological strata are not horizontal, and the ground 
water therefore is in motion, and where there is a surface run-off, 
have failed to establish any lowering of the water table under 
the forest ; also, that Hartman, hydraulic engineer for the State of 
Bavaria, found the water at Mindelheim (altitude 2000 feet) to 
be nearer the surface in the forest than outside. 
Hall and Maxwell in their work relating to stream flow and 
floods bring out the same facts. Hence, upon first thought, the 
inference might be drawn that in an essentially level state like 
Iowa the general effect of forest areas with respect to the water 
table would be to operate to the detriment of general agriculture. 
However, in view of the many other influences which already 
have been established, the question arises as to what part forests 
really may have in governing the soil moisture content of a region 
in general and the direction or tendencies of water movement 
in the soils. In other words, how great a conservator of moisture 
is a forest in an essentially level region ? 
In this connection, the conclusions drawn by Shimek are per- 
tinent, namely, that the question of sufficient soil moisture in a 
region such as Iowa is one of conservation of the precipitation, 
that the claim that forests have no effect on precipitation has 
27 Zon, Raphael, Rept. National Waterways Commission, Appendix V, pp. 238-245, 
28 Shimek, B., fiab. Nat. Hist., Univ. Iowa, 6, 207-208. 
