November, 1954 
of runoff water flowing into the lake. 
After large rains, this exchange of water 
is extensive. Most of the runoff water, 
when warmer than the bottom water, 
flows from the upper end of the lake to- 
ward the lower end at surface or near- 
surface levels. The bottom water is re- 
placed by water from strata lying imme- 
diately above; the lowest and coldest lay- 
ers are lost through the tower spillway. 
The magnitude of change (increase) in 
the temperature and dissolved oxygen con- 
tent of waters in the bottom strata of the 
lake following a period of rainfall is de- 
pendent upon the volume of runoff water 
draining into the lake from the watershed. 
When the volume of runoff water is great 
enough to exceed the capacity of the tower 
spillway and raise the lake level above 
the crest of the surface spillway, the 
water discharge from Ridge Lake becomes 
a combination of surface water and bot- 
tom water. 
In 1942, persistent thermal  stratifica- 
tion of Ridge Lake, characteristic of the 
warm seasons, began on April 4, figs. 5 
and 6. Prior to this date the lake ap- 
peared to be thermally stratified for short 
periods ; in each of these periods, the strati- 
fication was broken up by cold weather, 
DISSOLVED OXYGEN, RRM. 
MARGH 
APRIL 
BENNETT: LARGEMOUTH Bass IN RipnGE LAKE 
bo 
bo 
On 
which usually was accompanied by heavy 
rainfall. 
Annually, during the period of summer 
thermal stratification, Ridge Lake shows 
a surface layer of warm water (epilim- 
nion) of 3 to 5 feet in thickness. In 
the thermocline, the layer of water below 
the epilimnion, the temperatures gradu- 
ally become lower toward the bottom. 
The thermocline may show a temperature 
gradient of 10 to 18 degrees F. within 
a perpendicular distance of only 18 feet. 
No indication is given of a hypolimnion, 
or stratum of water of uniform tempera- 
ture lying directly above the lake bottom. 
Early in April, 1942, the temperature 
of the water at a depth of 18 feet was 
46.5 degrees F., while the temperature 
of the water at the surface was 59.0 
degrees F. Between the first week in May 
and the first week in June, the temperature 
at 18 feet rose from 50.0 to 63.5 degrees 
F. while that at the surface rose from 
70.5 to 87.0 degrees F. The maximum 
temperatures for the 18-foot depth during 
the latter half of July and throughout 
August in 1942 ranged from 71.7 to 74.0 
degrees F. During this same period, sur- 
face temperatures varied between 80.0 and 
88.0 degrees F. 
Fig. 6.—Dissolved oxygen, parts per million, at 12-, 15-, and 18-foot depths in Ridge Lake, 
early March to late October, 1942. The rise in oxygen during the month of June was due to 
the replacement of stagnant bottom water forced out of the lake through the spillway tower by 
surface water entering the lake from rains that fell on the watershed. 
