to 3 days. In the lower estuary, flushing is slow due to the large volume and 

 low nontidal currents. 



Union River estuary . No hydrographic data are available for the Union 

 River but the Ketchum model has been used, with the upper limit of the estuary 

 set at the Ellsworth dam and the lower limit at the end of Union River Bay. 

 The model shows that, except for the river and the upper part of the bay, the 

 estuary will have close to oceanic salinities (figure 5-20). This, in turn, 

 results in long flushing times at the upper end of the estuary and indicates 

 that materials discharged there would have a long residence time and high 

 accumulation in the bay. Further, the tidal velocities are low and thus 

 exchange of water due to tidal excursion (water leaving the lower part of the 

 bay on the ebb and being replaced by different water on the flood) would 

 contribute minimally to flushing. 



The low velocities in the upper narrow 4-mile (6 km) section and the rapid 

 change in salinity horizontally suggest that little vertical mixing occurs and 

 that vertical salinity stratification will occur at all times. In the bay, 

 stratification is likely to be similar to that in Penobscot Bay. 



Somes Sound . This estuary, Maine's only fjord, was studied in August, 

 1969, by Folger and coworkers (1972). Maximum depths within the Sound reach 

 50 m, and exchange of these waters with the adjacent coastal water is 

 restricted by 10 to 20 m depths at the mouth. 



In a typical fjord, this poor exchange would result in persistent thermal 

 stratification during the summer months and depletion of oxygen in bottom 

 waters as the result of decay of organic matter. However, Folger' s data do 

 not show evidence of this. Some thermal stratification (7°F;4°C) over the 

 upper 33 feet (10 m) occurs but dissolved oxygen concentrations are not low. 

 Salinity approximated oceanic levels throughout, with lower salinity occurring 

 only close to small streams near the head. Although this estuary is a fjord 

 morphologially, high tidal exchange results in sufficient mixing that 

 precludes its functioning as a fjord. 



A lack of fresh water flow data precludes application of the Ketchum model to 

 this estuary. 



Narraguagus River estuary . No hydrographic data exist for the Narraguagus 

 estuary, but the Ketchum flushing model can be applied (figure 5-21). 

 Although slightly larger than the Presumpscot and Royal estuaries, this 

 estuary is very similar to both. The entire salinity range from fresh to 

 oceanic is contained in the segment between Cherryfield and Milbridge (5 

 miles; 8 km). The volume is small and both tidal and nontidal currents are 

 high. The estuary probably is mixed well throughout and the residence time 

 is extremely short, so that the estuary ought to be well flushed. 



Machias River estuary . The Machias estuary is very similar to the 

 Narraguagus. No hydrographic data exist and the model predicts great 

 similarity between them (figure 5-22). Most of the salinity regime is 

 contained in the first 4 miles (7 km) of the estuary, tidal and nontidal 

 currents are high. This estuary ought to be mixed well and has short 

 residence times and rapid flushing. 



5-33 



10-80 



