The Commonwealth does hereby pledge to and agree with the United States and any other Federal agency that in the event that any Federal agency shall construct or loan or contribute any funds for the construction, extension, improvement or enlargement of any development project, or any portion thereof, the Commonwealth will not alter or limit the rights and powers of the department in any manner which would be inconsistent with the due performance of any agreements between the department and such Federal agency, and the department shall continue to have and may exercise all powers herein granted, so long as the same shall be necessary or desirable for the carrying out of the purposes of this act.