CAUSES INFLUENCING FLOW OF RIVER. 19 



likewise be ascribed in large part to the cultivated areas. Moreover, 

 the following- table shows that these Held pastures are even less favor- 

 able to water conservation, so far as concerns evaporation, than are 

 areas having- no surface growth at all. 



Comparison of evaporation, in (/rams, from a grass cover and from naked soil on arras of 

 1,000 square centimeters, April 15 to October 31, 187o. h 





Grass 

 cover. 



Naked. 





47, 355 

 51,721 

 55, 630 



18, 312 





33, 899 





30, 290 







b From E. Raraann's Forstliche Bodenkunde vind Standortslehre, p. 264. 



It is evident, therefore, that an open forest growth, which not only 

 gives access to sun and wind but also permits the invasion of grass 

 and weeds (the latter being notoriously more severe even than grass 

 in their drainage of water from the soil by evaporation), must affect 

 very unfavorably the moisture-holding capacity of the soil. 



The present report has now considered the various causes that may 

 have affected the flow of the Rock River. These have been found to 

 be a slightly diminished rainfall, increased drainage of agricultural 

 land, and changes in the extent and character of the forest. It has 

 been shown that, while it can not safely be asserted that forest destruc- 

 tion has produced any falling off in the annual precipitation over the 

 region, the amount of water which finds its way into the streams — that 

 is, the rainfall minus the evaporation — is somewhat less than it would 

 be had the original forest conditions remained undisturbed. It has 

 also been shown that clearing and use of the forest have combined to 

 produce a great diminution in the power of the soil to hold water, with 

 the inevitable consequence of a more rapid run-off and much wider 

 fluctuations in the volume of the river. 



If the changes in stream flow were the result of a climatic change 

 due to the general clearing of the land for farming, there would be 

 nothing further to be said. Since the restoration of primeval condi- 

 tions is an impossibility, the question of the effects which have fol- 

 lowed settlement and utilization of the land is one rather of scientific 

 interest than of practical importance. A proposition to reverse the 

 course of progress and turn an inhabited and productive district into 

 a wilderness in order to increase the rainfall would hardly appeal to 

 sane men. But when the main cause of the evils now complained of 

 is not the lack of rainfall, but the present inability to control the rate 

 at which the water is fed into the streams, the case is very different. 

 A careful examination of local conditions shows that there are w T ithin 

 reach feasible remedies, which should at least mitigate the irregularity 



