66 



BULLETIN 1017, U. S. DEPARTMENT OF AGRICULTURE. 



Table 15. — Storage capacity for the proposed Lake Traverse detention reservoir 

 south of White Rock, 8. Dak. 



Contours. 



Areas 

 within 

 desig- 

 nated 

 contours. 



Mean 

 areas = 

 volumes 

 when 

 lfoot 

 deep. 



Total 

 storage 

 capacity 



above 



elevation 



972. 



Contours. 



Areas 

 within 

 desig- 

 nated 

 contours. 



Mean 

 areas= 

 volumes 

 when 

 lfoot 

 deep. 



Total 

 ' storage 

 capacity 



above 



elevation 



972. 



972 



Billions 

 of sq.ft. 

 0.610 

 .680 

 .749 

 .811 

 .873 

 .915 

 .956 

 .976 



Billions 

 ofcu.ft. 



Billions 

 ofcu.ft. 

 0.000 

 .645 

 1.360 

 2.140 

 2.982 

 3.876 

 4.812 

 5.778 



980 



Billions 

 of sq.ft. 

 .996 

 1.017 

 1.037 

 1.065 

 1.092 

 1.121 

 1.149 



Billions 

 of cu. ft. 

 .986 

 1.007 

 1.027 

 1.051 

 1.079 

 1.107 

 1.135 



Billions 

 of cu ft. 

 6.764 



973 



0.645 

 .715 

 .780 

 .842 

 .894 

 .936 

 .966 



981 



7.771 



974 



982 



8.798 



975. . . . 



98I3-. . 



9.849 



976 



984 



10. 928 



977 



985 



986. . . 



12. 035 



978 



13. 170 



979 



990 1.243 















The relations of inflow, storage, and outflow are shown in the mass 

 diagrams of figure 20. It will be noted that, in these diagrams, the 

 15-day periods of no outflow have been taken in each case at a time 

 when their effect in producing high reservoir stages would be 

 greatest. 



In diagram E of figure 20, the estimated mean annual run-off, 

 " Inflow," was obtained by multiplying the mean monthly, 1909-1917, 

 run-off of the Minnesota Wild Rice by 1.6, the ratio of the watershed 

 areas, and deducting the loss by evaporation. The curve for the run- 

 off of 1916, diagram A, figure 20, the year of maximum precipitation 

 over the Lake Traverse watershed, was obtained by plotting as run- 

 off for each month, 20 per cent of the precipitation over the watershed 

 for the preceding month with the exception that 20 per cent of the 

 total precipitation for December, 1915, and January and February, 

 1916, was plotted as the March, 1916, run-off, the January and Febru- 

 ary run-off being merely nominal. This ratio (20 per cent) of run- 

 off to precipitation is the mean of those that prevailed immediately 

 after the great storms on the Red River watershed as indicated by 

 figure 19, and is considerably higher than is indicated for normal con- 

 ditions by the rather meagre data available. Diagram E shows that 

 with an outflow of 1,000 second-feet, starting May 1, the reservoir in 

 a mean year would be brought to low stage by about the middle of 

 June and that from that time on the outflow would at all times be 

 less than 1,000 second- feet. The maximum storage required would 

 be less than 2 billion cubic feet. In the case of run-off such as is 

 estimated for 1916 (diagram A) all run-off prior to May 1 could be 

 stored and the reservoir closed for 15 days during the summer, and 

 yet the reservoir could be emptied by the middle of December. In 

 that case there would be a maximum storage of 4.3 billion cubic 

 feet, which would not raise the water above elevation 978. 



In diagram B of figure 20, maximum spring run-off (January- 

 June) was plotted in combination with the summer and fall run-off 



