Vertical temperature distributions on a longi- 

 tudinal section of the lower estuary on a typical 

 summer and a typical winter day are shown in 

 fig. 4. 



The interior water at Station 7 and above 

 is cooler from November to March and warmer 

 from March through October than the water of 

 the lower estuary. EXiring the warm summer of 

 1955, the water temperature at Station 13 re- 

 mained above 20° C for about a month and a half 

 and above 15° C for more than three months, 

 while at Station 1 the temperature exceeded 15° G 

 for only a month and a half. The seasonal temp- 

 erature trends at four stations for a two-year 

 period are shown in fig. 5. 



In winter, ice forms in protected places 

 and where the water is brackish. The upper 

 estuary above the junction of Marsh River is 

 sometimes nearly completely frozen over . 



Bottom Sediments 



Detailed studies of the bottom sediments 

 of the estuary have not been made, but some in- 

 formation is available from U.S.C.G.S. charts, 

 Petersen -type grab samples, electronic fathome- 

 ter records, hand sounding lines, intertidal 

 samples and trawl and dredge samples . 



Most of the bottom is covered by a muddy 

 sediment composed largely of silt with some 

 fine sand and clay, as well as organic detritus. 

 Of the latter component, sawdust from numerous 

 now defunct sawmills is often a prominent fea- 

 ture . Much of the organic material may also be 

 derived from leaves, twigs, seeds, and other 

 terrestrial plant remains which lie in profusion 

 on the bottom . In the narrower parts of the 

 lower estuary and in much of the upper estuary, 

 where currents are strong, the bottom sediments 

 contain a large fraction of sand. Numerous and 

 sometimes extensive outcrops of bedrock inter- 

 rupt an otherwise relatively smooth bottom . 



Most of the intertidal area is either rock 

 or mud-flat. Sandy or gravelly flats are rare 

 except for a few exposed beaches near the sea- 

 ward end of the lower estuary and some small 

 sandbars in the upper estuary. Intertidal flats 

 usually show a zonation of sediments ranging 

 from coarse to fine from the high water level 



to the low. The reverse is true under certain 

 conditions, as in the case of the marginal flats 

 between grass marshes and tidal creeks with 

 fast currents . 



Silt is the predominant sediment in most 

 intertidal areas, however, and large quantities 

 of it are stirred into suspension with the flood- 

 ing tide to be redeposited on all exposed surfaces . 

 Intertidal sediments also contain much organic 

 debris, mostly sawdust or fragments of marsh 

 grass ( Spartina ) . 



Tides and currents 



Below the falls at Sheepscot Village the 

 mean tidal range is 9.5 feet, decreasing to 8 .9 

 feet at the extreme seaward end of the estuary 

 (U.S. Coast and Geodetic Survey data). Above 

 the falls the mean tidal range is about 6 feet, 

 there being about a 3 -foot drop in water level 

 over the falls at low tide. The tide continues to 

 ebb in the estuary above the falls for a little over 

 two hours after it has begun to flood below. Thus 

 the duration of the flooding tide above the falls is 

 only about four hours, while the ebb lasts about 

 eight. 



The inner estuary has a very high ex- 

 change ratio, that is, the relationship of the 

 volume of water entering or leaving during the 

 tidal cycle to the total high tide volume of the 

 basin. This exchange ratio averages about 0.7, 

 and results in swift currents and extreme tidal 

 fluctuations in salinity. 



Currents in the estuary have not been 

 studied in detail, but have been measured over a 

 complete tidal cycle in a few localities. By mak- 

 ing a few reasonable assumptions it is possible 

 to deduce a general picture of circulation patterns . 



Between the Sheepscot and Kennebec 

 estuaries is a system of shallow bays of irregu- 

 lar contour with three principal outlets: one 

 (Sasanoa River) into the Kennebec; one into the 

 Sheepscot near Station 3; and one into the Sheep- 

 scot near Station 7A. On the rising tide, water 

 enters the system from the Sheepscot through 

 the two latter channels and leaves on the ebb. 

 Water from the Kennebec enters through the 

 Sasanoa on the ebbing tide and, mixed with the 

 other water present, passes into the Sheepscot. 



