on succeeding days. In the summer of 1956 

 surface currents did at times approach a 

 state that might be called "typical" for 

 the bay (fig. 8). Yet this system was in 

 a continuous state of readjustment to chang- 

 ing winds and no single surface-current 

 pattern persisted over an extended period. 

 Movements of bottles, released on August 10, 

 give a good indication of surface currents 

 under fairly stable westerly winds (fig. 9). 

 Of 230 bottles released on this day only 

 one was recovered on the western shore. 

 Its travel cannot be determined since it 

 was out 99 days before recovery. Very 

 likely it first traveled easterly under the 

 west winds, became entangled in marsh weeds 

 along the eastern shores and then was re- 

 floated by strojqg easterly winds and carried 

 across the bay to the western shore. 



Under the influence of prevailing 

 easterly winds, surface currents travel 

 westerly in the bay as is demonstrated by 



the recoveries from bottle releases on 

 October 12 and 13 (fig. 10). Although 

 releases were made at fewer stations on 

 these dates than on August 10, it is clear- 

 ly evident from the recoveries that south- 

 east, east, and northeast winds caused a 

 general westerly surface drift. 



To indicate more clearly the relation- 

 ship between local winds and drift-bottle 

 travel, the release and recovery points of 

 the drift bottles have been plotted, along 

 with the winds that blew a short time prior 

 and subsequent to release (Appendix). As 

 exajnples, three typical stations in the 

 bay have been chosen [an inner-bay station, 

 fig. 11; mid-bay station, fig. 12; and 

 outer-bay station, fig. 13 (see pages 14 

 and 15)], and drift-bottle travel will be 

 discussed on the basis of information from 

 releases at these stations. 



Nineteen recoveries were made from the 



STATUTE MILES 



"Figure 9. — Surface currents in Saginaw Bay 

 determined from travel of drift bottles 

 released on August 10, 1956, during a 

 period of moderate westerly winds. 



Figure 10. — Surface currents in Saginaw Bay 

 determined from travel of drift bottles 

 released on October 12-13, 1956, during a 

 period of strong southeast-northeast winds. 



13 



