In which year did India and Bangladesh sign the Farakka Treaty for sharing of the Ganga water?

The correct option is 1996.

The Farakka Barrage was constructed by India in 1975 to divert water from the Ganga River into the Hooghly River. This diversion led to disputes between India and Bangladesh (then East Bengal / Bangladesh) regarding the sharing of the river water during the dry season.
To resolve this issue, the Prime Ministers of both countries—H. D. Deve Gowda of India and Sheikh Hasina of Bangladesh—signed a comprehensive, 30-year treaty on December 12, 1996. This treaty established a formula for sharing the water resources at the Farakka Barrage during the dry season (January 1 to May 31).