The volume of water in the Great Lakes = 5000 cubic mile
The mass of water = 5000 × (1.6×103)3 ×103 Kg = 2.13 × 1016 kg
Since molecular weight of water is 18, the total number of molecules in water having a mass of 2.13×1016 kg
Since the abundance of deuterium is 0.0156%, we have total number of deuterium atoms is
= 7.13 × 1041× 2 × 0.0156 × 1016 = 2.22×1028
Now the fusion of 6 deuterium atoms gives an energy of 43 MeV, therefore the energy release per atom is
43/6 = 7.17 MeV
Hence the total release of energy of 2.22 × 1028 × 7.17 MeV = 1.6 × 1029 MeV