OVERFLOW OF RED RIVER OF THE NORTH. 



27 



plotting the average precipitation at stations having records covering 

 10 or more years. The maximum and the mean annual precipitation 

 as indicated on figures 6 and 8, respectively, have been greatest in 

 the southeastern portion of the watershed and have diminished in in- 

 tensity to the west and north. 



Average depths of monthly and annual precipitation in the seven 

 subdivisions (see fig. 5) of the watershed for the period 1892 to 1919 

 were computed. The depths averaged were measured at from 2 to 



NORT 



30" 

 SOUTH DAKOTA 



cd^ 



Fig. 6. — Total precipitation during 1896 on watershed of Red River of the North. 



12 weather observation stations in each sub-area. The total volume of 

 precipitation for maximum months and for months immediately pre- 

 ceding months when run-off above Grand Forks has been maximum 

 are shown in figure 9. 



As is indicated in the various figures and tables, maximum precipi- 

 tation for April, May, and November occurred in 1896 when the 

 annual precipitation was maximum. In 1900 occurred the maximums 

 for August and September but the total precipitation for that year 

 was considerably below the maximum. In no case has the maximum 

 for more than one of the remaining seven months occurred in a single 

 j^ear; each has occurred during a year for which the annual precipi- 

 tation was above the mean for the watershed. 



