vpward toward the northwest. MacLean (1963) summarizes several earlier 

 papers which gave estimates for the Great Lakes region as 0.1 to 1 foot 

 per 100 miles per 100 years. Long-term lake level fluctuations are 

 usually thought of as volumetric changes, predominantly climatic in 

 origin, which can be summarized as follows: 



where 



S = (P-E) + (I-O) 



S = change in storage volume 



P = precipitation in drainage area 



E = evaporation 



I = inflow 



= outflow 



These processes have been discussed by Day (1926), Bajorunas (1963), 

 Brunk (1961 , 1963) , DeCooke (1968) , Richards and Irbe (1969) , and Rowe 

 (1969). 



Using the discharge values, basin areas, and precipitation volijmes 

 given by DeCooke (1968) , it can be seen that all of the above processes 

 are of the same order of significance in determining Lake Michigan -Huron 

 levels. For example, the rate of inflow to Lake Michigan- Huron from Lake 

 Superior, via the St. Marys River is about 40 percent of the rate of 

 outflow from Lake Michigan-Huron to Lake Erie, via the St. Clair River. 

 The remaining 60 percent is supplied by precipitation within the Michigan- 

 Huron basin. By using an annual rainfall rate of 31 inches per year, the 

 total precipitation falling in the basin is roughly 3 times that required 

 to account for the balance of the volume of water in the lake. Therefore, 

 evaporation must be roughly two -thirds of precipitation and removes more 

 water from the basin than does outflow. Furthermore, since evaporation 

 is greater on sunny, dry, windy days, and during the growing season, the 

 timing of precipitation as well as its total annual contribution becomes 

 a major factor in determining lake levels. Timing of ice formation on 

 the Great Lakes is an additional factor affecting evaporation and inflow- 

 outflow rates. Deviations in any of these processes from their average, 

 balanced rates lead to changes in water storage volumes and therefore in 

 long-term lake levels. 



V. GENERATION AND MOVBIENT OF BED FORMS 



Fluid motion, including wave oscillations and steady currents, inter- 

 acting with a bed of loose sediment results in a variety of features that 

 have been classified under the term bed forms. Different flow conditions 

 (tranquil, rapid, steady, and reversing) produce different and often 



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