202 LAND DRAINAGE 



265. Increasing the run-off. The removal of forests, 

 the breaking of prairies, and careless cropping and indif- 

 ferent tillage of lands after they are brought under culti- 

 vation all tend to increase the percentage of precipitation 

 which fails to enter the ground, but instead runs off as 

 surface drainage. Natural vegetation, whether forest or 

 prairie, with the resulting earth covering, permits the 

 excess of precipitation to move off so slowly that a very 

 considerable portion of it enters the soil to become ground 

 water and thus, to become " cut-off " water instead of 

 " run-off " water. The absence of the forest and prairie 

 conditions, and the compacted or puddled soil which is 

 likely to result from bad soil management, increases the 

 run-off and decreases the cut-off. 1 



266. Increasing evaporation. The removal of forest 

 and prairie vegetation and the indifferent management of 

 cultivated land undoubtedly result in great losses by 

 surface evaporation. It may be questioned, however, 

 whether the mere removal of forest and prairie vegetation 

 need increase evaporation losses, if honest, intelligent 

 soil management were followed. But it too often is not. 



267. The removal of surface reservoirs. It is con- 

 tended by some that the draining of ponds and swamps 

 by open ditch or tile drain removes water, much of which 

 would eventually find its way, by gravity, to become a 

 part of the great underground supply, and that as a part 

 of this supply it would eventually become distributed to 

 points quite remote from its original point of storage. 

 This is probably correct, in part at least. It may very 

 reasonably be questioned, however, whether this replen- 

 ishment of the underground water supply would prove of 



1 For definition of cut-off, run-off, and fly-off, see F. K. Cam- 

 eron, The Soil Solution, p. 22. 



