The problem with letting states figuring it out themselves is that water doesn't care about borders.
If a state unilaterally decided to suspend all contracts, treaties, and convenants on the sharing of hydrologic resources, other states would call on the federal government to step in. If the federal government refused to intervene, you would probably see aggrieved states form a coalition to force the "aggressor" state to cease "hostilities". Worst case scenario, it becomes a free for all and states start invading one another to "open the rivers and reservoirs". You could see local right-wing militias and ordinary but armed citizens take matters into their own hands. This is how civil war happens.
If a state unilaterally decided to suspend all contracts, treaties, and convenants on the sharing of hydrologic resources, other states would call on the federal government to step in. If the federal government refused to intervene, you would probably see aggrieved states form a coalition to force the "aggressor" state to cease "hostilities". Worst case scenario, it becomes a free for all and states start invading one another to "open the rivers and reservoirs". You could see local right-wing militias and ordinary but armed citizens take matters into their own hands. This is how civil war happens.