PART VIII — AQUATIC ECOSYSTEMS 



Figure VIII-12 — UPWELLING OF COASTAL LAKE WATERS 

 ^ WIND ^ 



(1) 



»- -► 



»~ 



(3) 



> v V V V V J ? \ 



\ V O f 



V 



V 



^ <> 



NEGLIGIBLE FLOW 



(4) 



20- 



40- 



60- 



WINDERMERE NORTHERN BASIN 

 26 OCT. 1949 



The circulation and upwelling produced by the stress of a steady wind on a small 

 lake is shown hypothetically in sketches (1) to (3). In diagram (4) the actual 

 thermal distribution is shown after 12 hours of wind stress. At the upwind end 

 of the basin, the thermocline intersects the water surface. 



are not at all accurate in a wave zone. 

 An important recent addition to in- 

 strumentation has been the airborne 

 infrared thermometer, which should 

 be exploited more systematically in 

 the future. Apart from this instru- 

 ment and the fluorometer used in 

 diffusion studies, we are still relying 

 on crude, ancient devices quite un- 

 worthy of the Space Age. 



Scientific Recommendations 



A most encouraging recent devel- 

 opment is that many fluid dynami- 

 cists previously in aerospace research 

 are turning their attention to lake 

 dynamics. This should be encour- 

 aged to the fullest possible extent. 

 The full understanding of the basic 

 dynamics of lake motions (where di- 

 rect effects of turbulence are un- 

 important) should be well within the 

 reach of fluid dynamicists today, and 

 should also provide important in- 

 sight into the somewhat less manage- 

 able problem of ocean dynamics. 

 Further, studies of internal zoaves and 

 turbulence (including their interac- 

 tion) also promise to be fruitful for 

 the understanding of mixing proc- 

 esses, particularly mixing through 

 stable layers. At the same time, 

 knowledge so gained is also relevant 

 to certain atmospheric problems, no- 

 tably to the understanding of clear 

 air turbulence. Experimental studies 

 of internal waves and turbulence are 

 more easily done in a lake than 

 30,000 feet up in the atmosphere. 



From a practical point of view, the 

 greatest urgency attaches to coastal- 

 zone studies of mass transport, cur- 

 rents, and diffusion. Present knowl- 

 edge in this field is quite inadequate 

 for even the crudest engineering de- 

 cisions. For example, the cooling- 

 water system for a large power plant 

 next to one of the Great Lakes was 

 designed on the basis of an under- 

 estimate of "typical" current speeds 

 by an order of magnitude; as a result, 

 the cooling water in that plant now 

 frequently recirculates from outlet to 

 intake, raising the cooling-water tem- 



256 



