Currents in a Strait 



543 



^/ = o = 



lAnM^ f y + l 



y-l 



^ \x'' + (j + 0' x^ + iy- 0' 



AAj^MJ i X 



v2 _ j2 _|_ /2 



[.^2 + + /)2] [.x2 + (j - O^]/- (XVI.33) 



If >'2 — x^ = /2 then h vanishes, that is, the lighter river water fills only the volume 

 between the hyperbolic branches y^ — x^ = P and jc = 0. The river water flows as an 

 upper layer over the lower layer, spreading out laterally between these hyperbolic 

 branches. The first term in (XVI.29) modifies this simple symmetrical spreading of the 

 river water on top of the lower water. This is purely an effect of the lateral and vertical 

 mixing process ; it causes the homogeneous layer to be deeper on the right-hand side 

 and shallower on the left-hand side. The inflow is thus directed to the right in the 

 Northern Hemisphere. Figure 25 1 shows the limits of the river water for the different 

 cases 



A^ 500 



2 

 500 



4 

 500 



500 



16 

 500 



and 



32 

 500 



where the dashed curve is for / = (non-rotating system). 



Table 145 



Exchange coefficients for the cases shown in Fig. 257 are contained in the following 

 Table 145 for a corresponding river mouth width 2/ and for/= 10~^ sec~^. The Coriolis 

 force deflects the seaward flow towards the right and gives rise at the mouth of a river 

 in the Northern Hemisphere to a water level sloping from the right bank down to the 

 left bank. For the lateral exchange coeflicients found in practice, 10^ to 10^, and for a 

 river mouth width between about 300 m and 1 km there will be quite a sharp deflec- 

 tion to the right (approximately as in curves d to/). The flow of river water into the 

 sea at the mouth of a river is shown schematically in Fig. 251a and conditions actually 

 found in nature will probably correspond reasonably well to this. 



