The model predicts that the lower part of the estuary will have high 

 salinities, approximating oceanic salinity, with maximum tidal velocities in 

 the lower estuary just south of Wiscasset. The narrow rocky channel should 

 have a considerable degree of mixing and may be an important factor in 

 determining the upper extreme of the two-layered flow regime. This is 

 evident in the steepening of the isopycnals (lines of equal density; figures 

 5-16 and 5-17) in both summer and winter (Garside at al. 1978). The lower 

 estuary has a permanent pycnocline, which in summer depends on both 

 temperature and salinity and in winter on salinity alone, and which has an 

 inverse temperature structure (lower temperature at the surface and towards 

 the head of the estuary). Stickney (1959) concluded that the uniform vertical 

 temperature structure in the fall resulted from vertical mixing but this is 

 probably not so, as the salinity stratification still remains then. 



The mixed water from the narrow channel south of Wiscasset flows southward and 

 to some extent is diluted further by fresher water entering from Goose Rock 

 passage. This fresher water stays to the west of the estuary and flows 

 southward into the Gulf of Maine (Stickney 1959). Below the surface layer (10 

 m deep), water having relatively high salinity enters the estuary (Stickney 

 1959) and Garside and coworkers (1978) identified the oceanic source of this 

 water as Maine Intermediate Water, based on its nutrient content (see 

 "Hydrography," page 4-11 in chapter 4). 



The surface tidal excursion of 2.8 miles (4.5 km) measured off mid-Barters 

 Island compares well with the mean tidal current (0.5 mile/hour or 3 

 miles/tide; 0.8 km/hr or 5 km/tide) predicted by the model. These same 

 current measurements and associated salinity measurements are typical of 

 patterns in partially stratified estuaries and are confirmed by extensive 

 measurements of the salinity distribution (Garside et al. 1978). 



Hockomock, Montsweag, and Nubble Bays . These irregularly shaped bays lie 

 between the Kennebec and Sheepscot Rivers and connect with them at Wiscasset, 

 Goose Rock Passage, and the Sasanoa River, respectively. These connections 

 provide for a cross exchange of water between the two estuaries. According to 

 Stickney (1959), water enters from the Sheepscot on the rising tide and leaves 

 on the ebb; the reverse is true for the Kennebec. Considerable mixing occurs 

 within the bays, so that the salinity of water returning to the estuaries has 

 been modified by the waters of the bays. Higher salinity water should be 

 returned to the Kennebec and lower salinity water to the Sheepscot. 



The inflow and outflow of the bays are not in phase with the estuarine tides. 

 Water flows into the Sheepscot from Hockomock for about an hour after the 

 start of its flood and the maximum flow out of Hockomock occurs about 3 hours 

 after the start of the ebb on the Sheepscot (Stickney 1959). The Maine 

 Department of Environmental Protection (DEP; 1979) conducted a survey to 

 examine the distribution of Kennebec River Water (KRW) in these bays and in 

 the Sasanoa River. They concluded, based on surface salinity measurements, 

 that some of the KRW was impounded in Montsweag Bay on each tide and the 

 remainder was discharged to the Sheepscot. They observed also a surface (8 

 ppt) to bottom (20 ppt) salinity gradient at Preble Point (junction of 

 Kennebec and Sasanoa rivers). This highly saline water could only originate 

 in the Sheepscot and suggests a two-layered flow, west to east at surface and 

 east to west at deeper levels, throughout the Sasanoa River. 



5-27 



10-80 



