; or (2) affects any authority of a State, as in effect on the date of enactment of this Act, to manage water resources within that State. 7. Authorization of appropriations (a) Authorization There are authorized to be appropriated such sums as are necessary to carry out the planning, design, and construction of the Water Systems, substantially in accordance with the cost estimate set forth in the applicable feasibility study or feasibility report described in section 4(a). (b) Cost indexing (1) In general The amount authorized to be appropriated under subsection (a) may be increased or decreased in accordance with ordinary fluctuations in development costs incurred after the applicable date specified in paragraph (2), as indicated by any available engineering cost indices applicable to construction activities that are similar to the construction of the Water Systems. (2) Applicable dates The date referred to in paragraph (1) is— (A) in the case of the Dry-Redwater Regional Water Authority System, January 1, 2008; and (B) in the case of the Musselshell-Judith Rural Water Authority System, November 1, 2014.