The right thus acquired by any such local interest is declared to be available to the local interest so long as the space designated for that purpose may be physically available, taking into account such equitable reallocation of reservoir storage capacities among the purposes served by the project as may be necessary due to sedimentation, and not limited to the term of years which may be prescribed in any lease agreement or other agreement with the Government, but the enjoyment of such right will remain subject to performance of its obligations prescribed in such lease agreement or agreement executed in reference thereto. Such obligations will include continued payment of annual operation and maintenance costs allocated to water supply. In addition, local interests shall bear the costs allocated to the water supply of any necessary reconstruction, rehabilitation, or replacement of project features which may be required to continue satisfactory operation of the project. Any affected local interest may utilize such facility so long as it is operated by the Government. In the event that the Government concludes that it can no longer usefully and economically maintain and operate such facility, the responsible department or agency of the Government is authorized to negotiate a contract with the affected local interest under which the local interest may continue to operate such part of the facility as is necessary for utilization of the storage space allocated to it, under terms which will protect the public interest and provided that the Government is effectively absolved from all liability in connection with such operation.