A NEW METHOD OF ESTIMATING STREAM-FLOW 229 
delivered to the reservoir could be similarly predicted by equation (8G), in which 
the net melting is estimated by equation (92). 
For a low-head plant fed by a shallow reservoir of large area, such as the one 
at Keokuk, Iowa, a change of elevation of the reservoir surface of a few hundred t ha 
of a foot is highly important from the operating standpoint. In such a case it is 
pertinent to note that the determination of the elevation of the reservoir BUrface at 
any hour may be considerably in error because of the effects of winds and baroinrt ric 
pressures upon it. It is claimed that in such a case, the highest attainable efficiency 
in use of water could be effected by taking account of these effects, and by fore- 
casting the yield to the reservoir by methods developed in this investigation. 
APPLICATION TO DETERMINATION OF EFFECTS OF FOREST COVER ON RUN-OFF 
If the denudation of a watershed of its forest cover has any effect upon run-off, 
that effect should be expressible in terms of the physical constants of the stream, 
S c , the R"s, the R'/s, C, F, M, T", G and E,/E w . If the presence or absence of 
forests makes no difference upon run-off, the stream-flow formulas derived from 
parallel observations of stream-flow and the weather elements during an epoch 
before denudation should be identical with the formulas derived after denudation. 
If the character of the run-off varies with variation in the amount of vegetal cover, 
that variation should be expressible qualitatively and quantitatively by the 
methods developed in this investigation. 
It would be too much to claim that, in its present stage, the method of analysis 
would be superior to the excellent studies recently completed at Wagon Wheel 
Gap, Colorado, for the purpose of settling that question, by the Weather Bureau 
and Forest Service. Its present degree of accuracy may not be great enough to 
warrant such a claim for such a scientific application. Indications are that the 
accuracy can be increased, however, and in this sense the method has potential 
merit which should make it a useful instrument by which to corroborate those con- 
clusions. It certainly has the advantage over the Wagon Wheel Gap method in 
being applicable to many watersheds in any past time for which the necessary, 
ordinary observations are available. 
SUMMARY OF GENERAL CONCLUSIONS TO PART II 
The principal conclusions to the stream-flow part of this investigation are 
here briefly summarized for the convenience of anyone who wants to get a general 
view of the results of this part of the investigation. Page references enable those 
interested to look up the basis of particular conclusions. 
General formulas have been derived, which express the relationship between 
the daily flow of a perennial stream in a moist climate, on the one hand, and the 
meteorological elements of rainfall, snowfall, vapor-pressure, air temperature, and 
wind velocity observed on its watershed, on the other hand. The principal ones 
of these formulas are equations (33) and (37). They involve, indirectly, other 
formulas, such as equations (34), (35a), (36) and (67) (pages 135 to 139, 156 to 158). 
Specific formulas have been developed for Streams A and B, Wagon Wheel 
Gap, Colorado, which enable one to estimate the daily flow of those streams with a 
fair degree of accuracy, from the five weather elements stated in the preceding 
paragraph as observed on their watersheds. These formulas are, for Stream A, 
equations (76) and (87), pages 168 and 178, respectively; and for Stream B, equa- 
