to Saginaw Bay, the Saginaw River at the 

 southwestern end is the largest. It follows 

 that the net flow of water must be from the 

 southwestern end of the bay northeastward 

 into Lake Huron. 



north side and a similarly distributed 

 outflow on the south side. They thought 

 that the winter circulation might be the 

 same as that in the spring or fall. 



The greater portion of the bay is less 

 than 20 feet deep. It is only near Lake 

 Huron at the mouth of the bay that a well- 

 formed, persisting thermocline is present 

 in the summer and early fall. Temporary 

 stratification does, however, occur within 

 the bay during the Rummer. In 1956 a ther- 

 mocline developed in certain inner areas 

 but it was ill-defined and temporary. 

 Approximately 25 percent of the total area 

 of the bay became stratified and almost all 

 of this area was at or near the mouth. 



Previous studies 



Both Harrington (1895) and Ayers et al . 

 (1956) were concerned primarily with circu- 

 lation in Lake Huron proper, although the 

 latter released "bottles" in the bay, and 

 both had recoveries here. According to 

 Harrington (1895) the most marked feature 

 of the drift in Lake Huron is the stream 

 passing southward along the west shore and 

 crossing the mouth of Saginaw Bay. The few 

 bottles that entered the bay during his 

 investigation landed in the northwestern 

 and southeastern sections. He did not com- 

 ment on circulation within the bay. 



The Saginaw Valley Project is of inter- 

 est here even though no current studies 

 were made (Adams 1937). For the summer and 

 fall of 1935 and the summer of 1936, it is 

 apparent from the study that there was 

 little or no correlation between chloride 

 concentrations in different areas of the 

 bay and wind direction. 



Ayers et al. (1956) noted changes in 

 circulation at the mouth of the bay in 

 different months. They believed that in 

 June 1954 there was inflow on the north 

 side and outflow along the south side. 

 Some inflow in July was thought to be sub- 

 surface with outflow spread over much of 

 the surface. Conditions in August were 

 held to be similar to those of July. They 

 conjectured from their limited data that 

 Saginaw Bay may behave like a simple estu- 

 ary of the same geographical orientation; 

 hence, in the autumnal circulation there 

 would be inflow at all levels along the 



Drift-bottle movements in 1956 



In our investigations, analysis of the 

 drift-bottle returns from releases in Sagi- 

 naw Bay confirms the belief of Ayers et al. 

 (1956) that no one stable surface-current 

 pattern exists within the bay. In fact, 

 results disclose more variability of the 

 surface currents than their studies were 

 able to show. It appears that the dynamics 

 of the bay are closely related to the highly 

 variable meteorological conditions of this 

 area and that the surface currents are in 

 a continuous state of change. For this 

 reason, we must state specifically under 

 what conditions any particular surface- 

 current pattern was found. 



It is possible in Saginaw Bay for com- 

 pletely different current patterns to exist 



Figure 8. — Typical surface-current flow 

 for Saginaw Bay in the summer of 1956. 



12 



