WATER CIRCULATION AND ITS CONTROL 



By BAILEY WILLIS, E.M.C.E,, United States Geological Survey 



( Coiiiiiidcd) 



CONTROL OF RITN-OI'I'- lIIROliOIT GRAZING 



AliOr'l' twenty-five per cent, of 

 tlic area of the United States 

 is so situated with reference 

 to topographic and chmatic conch- 

 tions that it will hest raise hardy 

 grasses and must l)e devoted chiefly to 

 grazing. 1die ]:»rinci])al area is that of 

 the great jdains, extending from north- 

 western Montana around the hase of 

 the Rock Mountains to Texas, l)nt in- 

 cluding also ])orlioiis of the hasin re- 

 gion on the west. Within this area the 

 governing condition is a meager prv- 

 cipitation. The soils ai\' ai)propriate 

 to agrictilture, the mountain ranges 

 above the ])lains are suited to forestry, 

 but both agriculture and forestry re- 

 (|uire more water than the grass that 

 feeds herds, ,-md the\' are accordinglv 

 h'mited in distribution in this region. 

 The herdsman's prosperity dejKMKls ab- 

 solutely upon the grass. Tt is proved 

 beyond dispute that overgrazing injures 

 the grass, jiartially removes the protect- 

 ive cover, and promotes erosion. Ero- 

 sion eventually results in the removal 

 of all herbage, ])ro(lnces l)are, gullied 

 badlands, and makes restocking with 

 grass impossible. 



The method available to the lienls- 

 man for the linn'tation of run-off and 

 the prevention of erosion is to increase 

 the stand of the natural grass cover, 

 u])on which alone his lu-rds depend. 

 In some small areas he may find it 

 necessary to ado])t the usual nut hods 

 of agriculture to check erosion, estab- 

 lish soil, and re-cover the surface with 

 grasses, but in general that which any 

 intelligent herdsman does to main- 

 tain the range upon which his herds 



live is that which he must do to pre- 

 vent erosion and to limit run-ofif. Thus 

 intelligent grazing promotes both in- 

 dividual and general welfare. 



The ])reservation of grass upon the 

 senn'arid ])lains is of vital interest, 

 ])r(;balil)', to the farming states, Minne- 

 sota, Iowa, and Missouri, and even 

 more so to eastern Nebraska and Kan- 

 sas. If it be true, as stated in the 

 o])ening discussion of conditions of pre- 

 cipitation (p. 265), that radiation from 

 the hot ])lains checks rainfall, it would 

 follow, should they be eaten bare and 

 eroded to badlands, that the semiarid 

 climate would extend eastward. The 

 plains themselves would beeonu' more 

 arid, the farming districts adjoining 

 them would be afi'ected by prolonged 

 dnnights. and the climate wotild be 

 unfavorably modified as far east as the 

 western margin of the moist-air cur- 

 rents that flow north from the (iulf. 

 Iowa is interested in the grass that 

 grows in western Nebraska. 



FOREST CONTROL OF PERCOF^ATION AND 

 RUN-OFF 



The areas which must be kept for- 

 ested in North America comprise 

 twent\-si.\ ])er cent, of the whole conti- 

 neiU. ( )f the I'nited States niin'tcen 

 per cent. rec|uires forest protection or 

 will grow trees more profitably than 

 any other cro]). The necessity for this 

 amount of forests rests on two im])i'ra- 

 tive economic conditions, (i) the value 

 of forest ])roducts, and (2) the protec- 

 tion forests afford to other essential 

 needs and activities of civilized com- 

 nnmities. 



It is not proposed here to discuss for- 



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