134 A NEW METHOD OF ESTIMATING STREAM-FLOW 
OUTCOME OF THIS INVESTIGATION 
The outcome of this part of this investigation may be briefly stated as follows : 
(1) Approximate quantitative expressions of the fundamental laws of flow of 
two streams, A and B, Wagon Wheel Gap, Colorado, have been derived. These 
numerical expressions enable one to compute the daily flow of these two streams 
from the observed weather elements of wind velocity, air temperature,vapor pres- 
sure, rainfall and snow gagings with a reasonably good degree of approximation. 
(2) The general method has been developed by which such expressions can 
be derived for any stream anywhere in the eastern two-thirds of the United States 
where the annual rainfall is 20 inches or more from parallel observations of stream 
flow, as measured by the United States Geological Survey, or otherwise, and from 
the meteorological elements as observed by the Weather Bureau. 
(3) The relation of the new knowledge stated in (1) and (2) to three important 
problems has become evident. The three problems are: 
(a) The problem of increasing the length of record of flow of a stream, the 
hydrograph, as a basis for greater accuracy in the design of works for power, 
irrigation, sanitation and navigation. 
(b) The problem of forecasting the flow of a stream as a basis for increasing 
the economy of operation of hydro-electric power plants. 
(c) The problem of determining the effect of forest cover on the run-off from 
watersheds. 
ORDER OF PRESENTATION 
The order of presentation, briefly stated, is as follows: 
(1) The manner of setting up the least-square solution to determine the nor- 
mal flow of a stream is first given, including the theoretical basis for the observation 
equations. The principal facts in regard to the two final normal flow solutions are 
given, including the values computed from them. The manner of using these 
values to compute daily normal flows is set forth. 
(2) The manner of setting up the least-square solutions to determine the 
flood-flow of a stream is given, including the theoretical basis for the observation 
equations. The principal facts in regard to the two final flood-flow solutions is 
given, including the values computed from them. The manner of using these 
values to compute daily flood-flows is set forth. 
(3) The manner of setting up the least-square solutions to determine the laws 
of freezing and melting is given. The principal facts in regard to the two final 
solutions are given, including the values computed from them. 
(4) A statement of the accuracy of the computed normal flow is presented. 
(5) A statement of the accuracy of the computed flood-flow is presented. 
(6) A statement of the accuracy of the laws of freezing and melting is 
presented. 
(7) The over-all accuracy of the computed flow of the stream is discussed, and 
the evidence presented. 
(8) Some general conceptions with reference to the travel of water from the 
time it reaches a watershed as rain or in the frozen form to the time it is measured 
as stream-flow are presented. These conceptions are intended to aid one in making 
a first estimate of the equations of flow of any stream. The method of correcting 
thisjirst estimate from the actual observations is presented. 
