SOME PROBLEMS IN CONSERVATION 46 



in order Xo safeguard the great rivers which head in these regions, 

 for purposes of navigation, irrigation, and power. 



The United States Geological Survey has investigated a number 

 of projects along this line. The White Mountains, New Hamp- 

 shire, may be cited as fairly representative of methods employed 

 and results obtained. The work was divided into two parts, — 

 geologic and hydrometric — and was assigned to some of the most 

 competent and experienced men on the Survey. "The examina- 

 tion included a general geologic study directed to the considera- 

 tion of the relation between control of the forest lands and the 

 protection of the streams rising on these watersheds, and an 

 intensive hydrometric investigation directed to the consideration 

 of the relation between land control and stream regulation." 

 "'The results of the former study are largely negative, . . . the 

 ihydrometric investigation . . . yielded what is believed to 

 be indisputable evidence of an actual and measurable relation be- 

 tween forest cover and stream regulation." In a word it was 

 demonstrated that deforestation accentuates the rapid melting of 

 snow, the amount of run-oi¥, floods and soil removal, while 

 forestation operat>es in the opposite direction. 



Through deforestation, the vegetation cover is reduced, the 

 immediate run-off increased, and floods in the tributary streams 

 cause soil removal and transfer to the larger streams, with flatter 

 grades, where sedimentation occurs, obstructing transportation 

 and interfering wit h power development. 



In conclusion the main thesis of this paper is to direct attention 

 to the importance of water conservation from an agricultural view- 

 point in Iowa. The mean annual rainfall, about thirty-five inches, 

 is adequate when properly distributed in time and space. There 

 is no convincing e^ udence to show that agricultural operations or 

 deforestation exert any measurable influence on the amount and 

 distribution o£ rain. fall. Hydrometric measurements made by the 

 U. S. Geological S urvey prove beyond any reasonable doubt the 

 dependence of the run-ofif curve on the vegetative covering. Cor- 

 rect drainage instalHation puts the ground in condition to receive 

 the rain as it falls, reduces run-off to a minimum and avoids 

 drowning of growing crops ; proper cultivation prevents the too 

 rapid escape of soil moisture thus ensuring an adequate supply to 

 bridge over periods of drouth. Through drainage and cultivation 

 the intelligent fainu'er aids in bringing about the correct distribu- 

 tion of water in tim-e and space. Forested areas, natural and arti- 

 ficial reservoirs,. ten.d to equalize stream flow, and thereby reduce 



