Which states have Krishna water dispute?

The river Krishna emerging from the western Ghat of Mahadeva Range of Mahableshwar in Maharashtra flows through the states of Maharashtra, Karnataka and Andhra Pradesh, ultimately, merges into the Bay of Bengal. 

A dispute amongst these riparian States namely, Maharashtra, Karnataka and Andhra Pradesh (erstwhile States of Mysore and Hyderabad, respectively) had arisen earlier also. A Tribunal was constituted for adjudication of the dispute. The States of Madhya Pradesh and Orissa were also parties to the dispute initially, but later these two states were discharged, as agreed to by all the parties. 

Further Reading:

• Inter-State Water Disputes Tribunals in India
• Interlinking of Rivers