ends, so that propagation upstream is quite vital in this case, also, and thus one needs 

 to consider the waves that are going in both directions. 



I will cut this short by showing a few slides giving the results of calculations 

 at the junction of the Ohio and Mississippi, and in the Kentucky Reservoir. 



The first slide (Fig. 1) shows stage at Cairo, at the junction of the Ohio and 

 Mississippi, and this is a prediction for sixteen days. (Stage means height of the river.) 

 One sees that the flood stages are predicted quite accurately. This was done on the 

 UNIVAC, and the calculation requires a few hours of UNIVAC calculating time. That 



312 

 H 

 308 



304- 



300- 



Stage at Cairo 



observed stages 



computed stages 



Jan. 15 



23 



27 



t 

 date 



is a lot of calculating, since the UNIVAC can do a great deal in two hours time. In 

 addition to the initial state of the system (i.e. the initial stage and velocity at all points), 

 the flows at the upper end of the Ohio and Mississippi are assumed known over the 

 whole time of the prediction. The second slide (Fig. 2) shows the results at Hickman, 

 below Cairo, in the lower Mississippi, and again this shows stages for a sixteen-day 

 forecast. At Hickman, the relation between stage and discharge was known. This is 

 an impedance condition which simulates the effect of the rest of the Mississippi below 

 that point. As one sees, the observed flood and the calculated one agree very well in 

 this case. The difference is a matter of inches, even in a period of two weeks. 



The third slide (Fig. 3) gives our results for the Kentucky Reservoir. The 

 lowest curve is for Kentucky Dam, at the mouth of the Tennessee. The next one above 

 is Perryville, somewhere near the center of the reservoir, some eighty miles upstream 

 from Kentucky Dam. Pickwick Dam is the dam at the upper end of the reservoir. 

 The length of this reservoir is about 186 miles. 



Again we were given initially the state of the reservoir. That is, flow velocity 

 and depth or stage were known throughout the reservoir at the initial instant. The 

 discharges out of Kentucky Dam and into the reservoir from Pickwick Dam were given, 



41 



