SOME OBSERVATIONS ON FORESTS AND 



WATER^FLOW 



By J, T, ROTHROCK 



THE report, '"The Influence of For- 

 ests on Climate and on Floods," 

 recently published, by Willis L. 

 Moore, chief of the United States 

 Weather Bureau, though quite full and 

 apparently intended to discuss in detail 

 the entire relation of forests to water- 

 flow, singularly enough omits entirely 

 one most important aspect of the 

 problem. 



So far as I can discover, little, if 

 anything, is said specifically of the in- 

 fluence of forests on water-flow during 

 the iviiitcr. 



The least reflection should have in- 

 dicated that this merited special con- 

 sideration, if for no other reason than 

 that the problem of leaf-evaporation is 

 almost wholly eliminated at that time 

 and that this would materially afifect 

 the quantity of water retained by the 

 soil for flow at the period of low-water 

 stage. 



There is, however, another and more 

 direct relation to be considered, which 

 seems to me to be of great importance. 

 It is the capacity which the forest floor 

 has /// zciiitcr for receiving and retain- 

 ing moisture as contrasted with the 

 same power of the open, cultivated 

 land, at tiie same time. 



I am led to call attention to this by 

 some observations made by me during 

 the last winter : 



It will be remembered that the sum- 

 mer, autumn, and early winter of 1909 

 were, in Pennsylvania — at least, in the 

 eastern half — of exceptional drought. 

 The soil was literally dried out. Springs 

 and wells which had not, within the 

 memory of living men, failed, ceased 

 to flow. Cattle were driven and water 

 hauled great distances. So it may be 

 fairly assumed that the soil in forest 



and in field was in a most receptive con- 

 dition for any rain which might have 

 fallen. December 13, there was, in 

 Chester County (Pennsylvania), a re- 

 markable rainfall of two and seventy- 

 eight one-hundredths inches, and there 

 was also some little snow before Christ- 

 mas. This moisture was speedily gone, 

 apparently, owing to the thirsty condi- 

 tion of the soil, and on Christmas day 

 the drought was again so pronounced 

 as to elicit general comment. There 

 had been but little added to the general 

 water-flow, and the country was still 

 in a very sulfering condition. 



On Christmas there was a fall of 

 snow which averaged in depth, on the 

 level, from sixteen to eighteen inches. 

 This was followed bv a lowered tem- 

 perature, and on the 28th the mean 

 thermometer was twenty-one degrees. 

 On the 30th the mean temperature was 

 ten degrees. December 31, it was 17 

 degrees. The ground was solidly frozen 

 to a depth of several inches. January i, 

 1910, the mean temperature was twenty- 

 seven degrees. January 2 it was forty- 

 three degrees, and on the following day 

 the mean was thirty-five degrees. It is 

 needless to say that the snow was melt- 

 ing rapidly, though it showed but little 

 corresponding flow in the fields, be- 

 cause, as the ground was frozen, most 

 of the water was absorbed by the snow 

 itself, and the country was in a slushy 

 condition. 



For several days I had been making 

 observations in the woods and on the 

 fields upon the condition of the sur- 

 face soil. In the woods, where the 

 leaves covered the ground, I found that 

 it was possible to thrust an iron-shod 

 cane without difificulty to a depth of 

 eighteen inches into the earth, unless 



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