I thought there were no major dams in Tibet, for the simple reason that India would rightfully protest and be in an uproar? Since essentially, it would put a significant portion of Indian fresh water supply under Chinese control. In that case, those dams would be a legitimate war time target, and India would rightfully throw everything they have at destroying those dams, even with the risk of flooding their own rivers: since the alternative would be risking having a significant source of their fresh water supply being cut off. If China did have dams in Tibet, then China would not even need to launch any sort of attack on India. China could just shut the hypothetical dams and defend them for two weeks before India capitulates.