The number of named lacustrine systems in each of the six coastal regions 

 ranges from 4 (region 1) to 58 (region 4; table 7-2). The total surface area 

 of all lacustrine systems, named and unnamed, in each of the regions ranges 

 from 426 acres (170 ha) in region 1 to 19,567 acres (7827 ha) in region 5 

 (table 7-1), while the average lacustrine area ranges from 96 acres (38 ha) in 

 region 1 to 355 acres (145 ha) in region 6 (table 7-2). The percentage of 

 land and freshwater area occupied by lakes ranges from <1% (region 1) to 5% 

 (region 5) of the total. These data clearly indicate that the lakes and ponds 

 in regions 1 and 2 are much smaller than those in regions 3 to 6, and that 

 their total surface area and percentage of total regional land and freshwater 

 area are also less. 



PHYSICAL CHARACTERISTICS 



Physical characteristics other than size data and habitat type of lacustrine 

 systems are available only for those lakes named on USGS quads. Eighty-four 

 (39%) lakes in the coastal zone exceed 100 acres (40 ha) in area (table 7-3) 

 and the largest, Gardner Lake (region 6) is 3694 acres (1495 ha). The largest 

 lakes in individual regions are: Highland Lake, in region 1, 261 acres (106 

 ha); Togus Lake, in region 2, 640 acres (259 ha); Damariscotta Lake, in region 

 3, 2034 acres (823 ha); Toddy Pond, in region 4, 2412 acres (976 ha); Graham 

 Lake, in region 5, 3278 acres (1327 ha); and Gardner Lake, in region 6, 3694 

 acres (1495 ha). (The parts of individual lakes lying outside the coastal 

 zone are not included in acreages above or in table 7-3.) Of the 27 municipal 

 water supply lakes (see table 7-2 for regional distribution), 14 are smaller 

 than 247 acres (100 ha) and 13 are larger (range 348 to 2275 acres; 139 to 910 

 ha). Region 4 contains the greatest number of lakes. Twenty-six lakes have 

 dams at their outlets (see table 7-2 for regional distribution). However, 

 these data are incomplete. The surface areas of 15 of these lakes exceed 1000 

 acres (400 ha). Thirteen of the dams are equipped with fish ladders and four 

 are equipped with fish screens (these data also are incomplete; see atlas map 

 4). 



The average summer surface temperatures of the lakes are almost uniform (71 

 to 78 F; 22 to 25°C; table 7-2). The percentages of named lakes that are not 

 thermally stratified (33% of the total), that are stratified without a 

 hypolimnion (297o) , or that are stratified and have a hypolimnion (37%), differ 

 among the regions. Descriptions of stratified lakes are given later in 

 "Lacustrine Limnology." 



The transparency of named lakes, based upon Secchi disc visibility in meters 

 in summer, ranged from 4 m (13.2 ft; region 2 mean) to 6.3 m (21 ft; region 5 

 mean), and averaged 5.5 m (18 ft) for 56 lakes (table 7-2). The one 

 observation of 9.1 m (30 ft) in region 1 is insufficient for comparison. 

 Differences in transparency show no consistent trends among regions. Further 

 physical data are given in appendix tables 1 and 2. 



Maximum depths of 180 coastal zone lakes are known (table 7-3; appendix table 

 1). Region 5 has the greatest number of deep lakes; 20% of the 52 lakes that 

 were surveyed there are deeper than 25 ra (83 ft) . The deepest lake in coastal 

 Maine, Tunk Lake (68 m;224 ft), is in region 5. Average surface tempertures, 

 average water transparency levels, and ratios of thermally unstratified to 

 thermally stratified named lakes vary slightly among regions. 



7-8 



