Several practices of the Health and Safety Department of TVA have 
definite bearing on wildlife welfare. These consist of operations for 
controlling the malaria mosquito larva (mainly Anopheles quadrimaculatus) 
by reducing its breeding environment and include the following: Water 
fluctuation, larvicidal treatment, plant control, shoreline conditioning, 
cutting and filling, diking and dewatering, and land-use restriction. 
Water Level Fluctuation 
The manipulation of water levels is considered an essential procedure 
for preventing the development of favorable breeding habitat for the malaria 
mosquito (Hall et al, 1946). The program calls for high water levels well 
above normal, in the spring of the year in order to strand floatage. This 
is followed by a period of constant water level until breeding of the 
malaria mosquito has passed the initial stage. Holding a constant water 
level restricts the zone of amphibious vegetation and contributes to malaria 
control by suppressing coppice growth. The constant~level period is followed 
by a weekly cycle of fluctuation. Later in the season, the weekly raising 
and lowering of the water level is combined with recession of about 1/10 
of a foot during each week. On all of the main-river reservoirs with the 
exception of the lowest impoundment, Kentucky Lake, this cyclical-recessive 
fluctuation is conducted through the summer into September when the breeding 
of the malaria mosquito ceases. On Kentucky Lake there is a gradual draw-~ 
down rather than a fluctuated one. 
The draw-down of water for malaria control results in stranding marginal 
vegetation some of which might otherwise be useful to waterfowl. It also 
prevents the growth of submerged plants. In this respect, malarial opera- 
tions might well be subject to undue criticism as inimical to waterfowl. 
Since, however, a later and more drastic draw~down for power and flood 
control occurs before waterfowl use of these TVA lakes, dewatering and 
stranding of vegetation takes place regardless of malaria control programs. 
Larvicidal Treatment 
Larvicidal control of Anopheles has involved the use of oil, Paris 
green, and DDT. The oil treatment is definitely harmful to wildlife, but 
fortunately, high costs of this method have reduced its use to a point where 
interference with wildlife is negligible. Though in the past some damage 
has resulted from dusting with Paris green, it has been found that this 
procedure can be conducted without harm to wildlife. Recently TVA has 
changed over to nearly exclusive use of DDT, mainly by plane. Under favor- 
able conditions, concentrations as low as .0l; pounds to an acre have yielded 
approximately 90% control of anopheline larvae (Metcalf et al, 1945). How- 
ever, higher concentrations are necessary when the vegetation is dense. 
For the most part, DDT is being applied here at the rate of less than .l 
of a pound to an acre. This treatment is devastating to larvae of Anopheles 
but fortunately causes little or no effect on other organisms that are 
important in the food chain for fish and other wildlife in the TVA region. 
