CHANNEL CONNECTING TWO RESERVOIRS OR LAKES 



93 



level in the lower pool until the Ml curve forming above the lower 

 pool level reaches the entrance to the channel. 



The Q curves in areas I and IV are plotted from computations made 

 as follows: If the control is at the upper end of the channel, the dis- 

 charge is first computed for various 

 elevations in the upper pool. Pro- 

 files for each discharge are then 

 computed to find the highest eleva- 

 tion in the lower pool that will not 

 cause reduction of discharge at the 

 control. If the control is at the 

 lower end of the channel, or at an 

 intermediate point, the discharge is 

 computed for various levels of the 

 water surface just above the control. 

 Profiles are then run upstream to 

 determine the upper pool level. The 

 highest pool level in the lower pool 

 that will not cause reduction of the 

 discharge at the control is finally determined, using profile computa- 

 tions if the control is at an intermediate point in the channel. These 

 computations fix the spacing of the Q curves in areas I and IV, and also 

 the position of the boundaries of these areas. 



In areas II and III the curves for constant discharge are tangent to 

 the Q curves of areas I and IV and asymptotic to the line Q = 0. 

 There is no control, and the relative values of the pool elevations have 

 to be determined by profile computations. For uniform channels, the 

 methods described in Chapter VII may be used for the profile com- 

 putations, with considerable saving of labor, but if the channel is 

 irregular, the step methods of Chapter IX must be used. If the 

 channel is fairly uniform, and in addition is broad and shallow, the 

 methods described in Chapter VI are most advantageous. 



5 10 15 20 25 30 



Water- Surface Elevation in Reservoir "B" 



Fig. 804. Discharge in Channel 

 Connecting Two Reservoirs. 



PROBLEM 



806. A channel 1 mile long and 400 feet wide, with nearly level rocky bottom and 

 vertical riprap sides, connects two lakes, the levels in which may vary up to 10 feet 

 above the channel bottom. Construct a diagram showing the flow in the channel 

 for all possible combinations of levels in the two lakes. 



