Jackson Gulch Rehabilitation Project Modification Act This bill amends the Omnibus Public Land Management Act of 2009 to modify provisions regarding the Jackson Gulch rehabilitation project, Colorado, to require the Bureau of Reclamation to cap the payment of the federal share of the total cost of carrying out the project at 65% of the total cost. The Mancos Water Conservancy District shall be liable for the lesser of 35% of the project's cost or $2.9 million, subject to a specified credit. Reclamation shall: (1) review and approve all final costs associated with the project's completion, and (2) credit the district for all amounts paid by the district for engineering work and improvements directly associated with the project. The district shall pay the project costs for which it is liable over a period of not more than 40 years. There are authorized to be appropriated to Reclamation to pay the federal share of the total cost of carrying out the project the lesser of not more than 65% of the total cost of carrying out the project and $5.35 million.