Sites Reservoir Project Act This bill directs the Bureau of Reclamation of the Department of the Interior to take certain actions related to federal support for the construction of water infrastructure in California. Specifically, with respect to the Sites Project (a water storage project in Glenn and Colusa Counties, California), Reclamation shall (1) be the lead federal agency for the purposes of all federal reviews, approvals, or decisions required under federal law to allow either Reclamation or the Sites Project Authority to construct the project; and (2) ensure that all such reviews, approvals, or decisions are completed by January 1, 2022. Reclamation must complete the final feasibility study evaluating the development of the project and, if the project is determined to be feasible, Reclamation may authorize additional funding and technical support. Reclamation must also work to facilitate the completion and issuance of the final joint environmental impact statement and report on the project. Reclamation shall, at the authority's request, enter into a partnership agreement for the authority to provide full project management control for construction of the project or a separable element of the project. Further, Reclamation must advance the project as a non-federal project, and the Department of the Interior must execute a long-term agreement with the authority for the coordination of operations of the Sites project and the Central Valley Project.