volume of the lake is given as 2.72 * 10^9 and we

  will assume that this volume is given in cubic feet

since one cubit foot of water equals about 7.5 gallons,

  we can determine the approximate number of gallons

  in the lake by dividing the volume by 7.5

(2.72 * 10^9) / 7.5 = 3.6266667e+08 = 36,266,670 gallons

this means the lake holds over 36 million gallons of water