inflow along the western shores and outflow 

 along the eastern shores was observed 

 several times during the sununer and fall. 



Lake Huron 



indicate that in open waters surface 

 currents also are variable. Apparently, 

 movement of water from west to east in 

 Lake Huron does not follow a straight line, 

 but direction changes several times before 

 it reaches the Canadiain shores. 



In Lake Huron the prevailing winds are 

 more important than local winds in forming 

 current patterns. The energy input intp 

 the lake by the prevailing wind is not dis- 

 sipated by temporary wind shifts. Currents 

 on any one day reflect the wind input of 

 the previous days (at least 12, according 

 to Millar 1952). The general drift in Lake 

 Huron was from west to east; it was caused 

 presumably by the prevailing westerly winds. 

 This finding seems to support Millar's 

 theory. On the other hand, bottles under 

 the influence of strong local winds moved, 

 at times, against the prevailing pattern. 

 The most marked of these exceptions to 

 pattern was the drift of bottles from east 

 to west around the tip of the Michigan Thumb 

 area where there is normally a strong cur- 

 rent in the opposite direction. Other 

 examples of this reversal against the pre- 

 vailing pattern were noted in the Tawas 

 Point-Au Sable Point area. Millar's state- 

 ment to the effect that the energy input 

 is not dissipated for several days might 

 not apply to the surface water; at least it 

 would seem not to apply in the above-cited 

 reversals. 



The effects of stratification upon 

 currents present an unsolved problem in 

 Lake Huron. The depth to which currents 

 are present in stratified lakes is still a 

 subject of much study. As Mortimer (1954) 

 has found, subsurface currents are, most 

 likely, present in water much deeper than 

 was formerly realized and, consequently, 

 are of some significance. 



Ayers' (1956) method of using dynamic 

 heights has contributed a new concept in 

 calculating surface currents of large in- 

 land lakes. But as he has suggested, this 

 method should always be checked by means of 

 other parameters to determine whether it is 

 giving valid results. His method may be 

 limited in some degree by the high ratio of 

 shoreline to surface-water area and the 

 confined nature of some areas of inland 

 basins. The shoreline, if appears, plays 

 an important role in conforming currents 

 into some pattern regardless of the dynamic 

 heights. Dynamic-height calculations 



RECOMMENDATIONS FOR STUDY OF CURRENTS 

 ON THE GREAT LAKES 



Current-pattern determination on the 

 Great Lakes is still in its earliest state 

 of development. The few studies available 

 leave much to be desired. Just what the 

 subsurface currents are and what their 

 relation to surface currents is remains a 

 matter of conjecture. Surface-current 

 observations have not extended over long 

 enough periods to support conclusions 

 regarding seasonal patterns. If the true 

 nature of currents in the Great Lakes is 

 to be determined, a program must be carried 

 out that will include the following points: 



1. Study one lake or one area of a 

 lake for a period of several years through- 

 out all seasons. Such a project should 

 disclose what forces are at work in forma- 

 tion of currents, and thus lay the founda- 

 tion for predictions of currents. 



2. Employ various methods in deter- 

 mining currents and check each method 

 against others and against known conditions 

 whenever possible. The relisibility of each 

 method could be ascertained and the limita- 

 tions of each determined. 



3. Study the degree of correlation 

 between meteorological conditions and 

 current patterns. Present methods of 

 recording wind data over the lake should 

 be refined. Recent evidence indicates 

 that large variations in the winds occur. 



4. Develop new equipment and methods 

 auid use devices other than drift bottles. 

 The transponding drift buoy as described 

 by Bumpus et^ aS. (1957) appears to hold 

 much promise as a current indicator. The 

 tracking of radio signals emitted from this 

 free floating buoy makes it possible to 

 determine its movement precisely. Investi- 

 gate the use of the radioactive isotope as 

 an aid in determining movements of water 

 masses. Recently, the City of Los Angeles 

 employed isotopes to determine the path of 

 the flow of sewage into the Pacific Ocean. 



26 



