116 
BULLETIN OF THE BUREAU OF FISHERIES 
the several species of fish, to present a general account of the physical and biological 
conditions of the lake based primarily upon observations of Mr. Stringham. 
AREA 
The effects of the dam are said to extend as far as Oquawka, 111., 41 miles (66 
kilometers) northeastward from Keokuk and 54 miles (87 kilometers) along the course 
of the lake and river; but the influence as far away as this is scarcely perceptible, 
and the upper end of the lake may, for convenience, be taken as at Burlington, Iowa, 
31 miles (50 kilometers) northeastward from Keokuk and 42 miles (68 kilometers) 
along the course of the lake (fig. 15). The general form between these two points is 
that of a drawn-out letter S or a compound curve, the outer edges of the curves being 
at Dallas City, 111., and just north of Montrose, Iowa, respectively. The width 
varies from about % to 2K miles (0.8 to 4 kilometers), as appears from a map prepared 
by the power company in 1913 or 1914. Subsequent raising of the water level may 
have increased this maximum width, and even on the map the width is greater where 
slender fingerlike projections extend out from the general border of the lake. 
The area of the lake, as roughly determined by applying a planimeter to the 
same map, was about 53.3 square miles (138 square kilometers), but this map does not 
include all backwaters. The records of the power company show that from the greatest 
level in 1914 (occurring January 29) to the greatest level in 1916 prior to September 
(occurring January 15) an additional 3.6 square miles (9.3 square kilometers) was over- 
flowed.. Part of this additional overflow would be above Burlington, which has been 
assumed to be, practically speaking, the upper end of the lake. Including all lateral 
backwaters, the total area of the lake in 1916 was probably in the neighborhood of 
60 square miles (about 150 square kilometers). According to information supplied by 
the power company, the lake was to be raised an additional foot, and the total area 
would then be nearly 70 square miles. Of course, there has been a large increase in 
volume of impounded water, and, by calculations made at the office of the company 
in June, 1917, this would amount to somewhere in the neighborhood of 14,000 million 
cubic feet, when the lake had been raised to the stage of 525 feet, Memphis datum. 
Unfortunately, from the viewpoint of the fisheries, the area of the lake has now been 
reduced substantially by the construction of levees and the reclamation of sub- 
merged lands for use in agriculture. The principal drainage district (covering the 
Green Bay region and lying between Fort Madison and the Skunk River) was drained 
during the winter of 1918-19; this reduced the area of the lake by 10 to 15 square 
miles. Under present conditions the area of the lake varies between 58 and 64 
square miles, depending upon the stage of the water. 
DEPTH 
The water depths for this region as it was are shown on Charts Nos. 136 to 140 of 
the survey made by the Mississippi River Commission in 1891. These soundings 
were made at low stages of the river, those for the rapids (Keokuk to Montrose, 
Iowa) being made while the river was at 1.5 feet on the Keokuk gage, or at 486 
Memphis datum. The greatest depth on the rapids was 15 feet (4.6 meters), and 
the depth along most of the channel was about 6 or 7 feet (about 2 meters). From 
Montrose north to Burlington there were some soundings of 26 feet (7.9 meters), 
but the depth of the channel did not average over 12 to 15 feet (3.7 to 4.6 meters). 
