482 DISCUSSION: FORESTS, RESERVOIRS, AND STREAM FLOW 
Mr. Chitten- variations will be observed in the rainfall for the same month, as well 
en, 
as from month to month for the same year, though the mean ‘monthly 
averages do not differ so widely. The comparative absence of freshets 
in the summer illustrates the influence of temperature. It is clearly 
not due to less rainfall in that season, since the average precipitation 
then is greater than during the flood months. * * 
“It will be found by a careful examination of these tables that 
usually the occurrence of the freshets is sufficiently explained by the 
monthly rainfall. Now and then discrepancies appear, especially dur- 
ing the flood months, as when a freshet accompanies an unusually 
small rainfall, or fails to accompany a comparatively large rainfall. 
In such cases an examination of the hydrograph usually shows that the 
small rainfall was concentrated in a few days, while the large one was 
distributed through the month and sometimes accompanied by several 
freshets that failed to reach the stage under consideration. It’ is 
believed that these considerations, making freshets entirely dependent 
on rainfall and temperature, fully meet the arguments of those who 
attribute their increase to deforestation.” 
Several interesting facts are disclosed in these tables. Note that 
practically the whole excess in number of floods in the second period 
occurred in the month of March and that it is all accounted for by 
excess of rainfall for that month. The effect of temperature has been 
pointed out. This, of course, acts not only through direct evaporation 
while a storm is going on, but through the greater absorptive capacity 
of the soil at such seasons, due to its drying out more rapidly when it 
is not raining, and to the heavy draft for the growing crops and trees. 
It takes a heavier rain at such times to produce a given result in 
stream flow than in the cold seasons of the year. Again, after a period 
of high rainfall, the precipitation for a month may produce a greater 
flood than the same precipitation after a period of light rainfall, other 
conditions being the same. A more minute study, going into the 
details of each storm, would be required to explain all discrepancies; 
but these monthly records go a great way in that direction and indicate 
the proper lines along which a study should be developed. The writer 
regrets that because of lack of time he could not carry this study to 
other water-sheds, but until it is so applied to every case, any pretense 
that changed flood conditions on such water-sheds are due to changes 
in forest areas is entirely without warrant. There is nothing in our 
existing state of knowledge to indicate that these records may not be 
completely reversed in the next ten years. 
It is submitted that the above exhibit effectually punctures the 
iridescent bubble which Messrs. Swain, Pinchot, McGee, and Leighton 
have set afloat in this discussion. Their vaunted criterion of a ten-year 
period is a pleasing pipe dream and nothing more. Their smoothing- 
out process is a smothering process. It suppresses the very facts that 
the engineer most needs to know. It substitutes a sham for the real 
thing. It is fundamentally unscientific. 
