157

approximate elevation of the Hoover Dike that surrounds the

lake.

 Under the new stage regulation schedule that will soon-

go into effect, an estimated 56,000 acres (22,800 ha) of

marsh will be exposed in driest years. The area of

seasonally-drying marsh will be reduced by more than 40%,

and approximately 37,000 acres (15,200 ha) of wading bird

feeding habitat will be lost.



 Relationship Between Water Levels and Fish Populations

 Land morphometry and fish populations were studied in

a typical marsh-pond system during its seasonal cycle of

expansion and contraction.


Contours

 In Figure 35 is a contour map of the Corkscrew area

that includes the study site, located in the approximate

center of the map. The map includes the higher land that

borders the marsh on the north. Elevations on the map

range from 16.5 ft (5 m) MSL at the edge of the pond to a

high of 29 ft (8.8 m) MSL. The marsh lies within the 18 ft

(5.5 m) contour line, and general elevations over the marsh

vary between 17 and 18 ft (5-5.5 m) MSL.

 Contours of the pond and a portion of the marsh

transect are shown in Figure 36. The contour map of the

pond is based on two perpendicular topographic survey lines

through the center of the pond and water lines determined