228 American Fisheries Society. 



soil. Originally this area of the state was clothed with a magnifi- 

 cent hardwood forest, known as the "Big Timber," covering nearly- 

 all the plateau-like uplands as well as the valleys, and the rich 

 soil and comparatively level uplands were first cleared and put 

 under cultivation beginning with the early forties, or over 80 

 years ago. 



.The actual systematic drainage of marshes and lakes covers 

 an immense territory in the southwestern, western, and north- 

 western counties, areas, into which we have so far carried on but 

 little investigation. What little we have done proves the conclu- 

 siveness of the disastrous results so far as they affect our future 

 water supply and the permanence of our streams. 



To what extent drainage, naturally resulting in a greatly re- 

 duced evaporation of moisture into the atmosphere during long 

 sustained hot weather, is going to affect the rainfall in years to come 

 is problematical, authorities differing greatly on this point; but it 

 seems to be utter folly to disregard its very probable effect on the 

 precipitation of the future. According to official sources (Water 

 Resources Investigation of Minnesota, St. Paul, 1912) we find the 

 mean annual rainfall of the Mississippi basin in Minnesota to be 

 27 inches, of which the run-off has varied from 5.1 to 23.9 per 

 cent of the total mean. At St. Paul, where records are continuous 

 since 1837, we find the wettest year (1849) gave 49.7 inches and 

 the driest (1910) but 10.2 inches of precipitation. However, the 

 precipitation appears to be heaviest in the southeastern part of the 

 State, where it is 33 inches, as compared with 24 inches in the 

 western part. The mean precipitation for the Root River basin, the 

 wettest in the State, is 32 inches, where the run-off reaches as high 

 as 27.7 per cent. We find the mean annual for the Red River 

 basin varying from 15 inches on its west border to 26 inches on the 

 east in the lake region; about 75 per cent of this total falls in the 

 six months from April 1 to September 30. The run-off here varies 

 from 5.9 to 23.1 per cent in the timbered region above Fergus Falls, 

 while from the prairie and timbered area below this it varies from 

 1.8 to 11.3 per cent. From this same report we find the rainfall 

 of the Des Moines basin in southwestern part of the State to be 

 25 inches. 



Even though we admit a normal annual rainfall still persists 

 over much of our territory, in the cultivated regions it now rushes 

 off immediately after every downpour, carrying soil and debris 



