; and (B) to investigate, implement, or improve a water conservation measure (including a metering or monitoring activity) necessary for the Nation to make use of a water right of the Nation under the Agreement. (3) Investment Beginning on October 1, 2019, the Secretary shall invest amounts in the Navajo Nation Water Resources Development Trust Fund in accordance with subsection (e). (4) Investment earnings Any investment earnings, including interest, credited to amounts held in the Navajo Nation Water Resources Development Trust Fund are authorized to be used in accordance with paragraph (2). (5) Authorization of appropriations There are authorized to be appropriated for deposit in the Navajo Nation Water Resources Development Trust Fund— (A) $6,000,000 for each of fiscal years 2010 through 2014; and (B) $4,000,000 for each of fiscal years 2015 through 2019. (6) Availability Any amount authorized to be appropriated to the Navajo Nation Water Resources Development Trust Fund under paragraph (5) shall not be available for expenditure or withdrawal— (A) before December 31, 2019; and (B) until the date on which the court in the stream adjudication has entered— (i) the Partial Final Decree