Mid-Valley Unit Act of 1987 - Authorizes the Secretary of the Interior to construct, operate, and maintain the Mid-Valley Unit of the Central Valley Project, San Joaquin Valley, California.

Authorizes the Secretary to provide water supplies for the irrigation of approximately 4,000,000 acres of land in California.

States that the conservation and development of fish and wildlife resources and the enhancement of recreation opportunities in connection with the Mid-Valley Unit shall be in accordance with the Fish and Wildlife Coordination Act and the Federal Water Project Recreation Act.

Directs the Secretary to execute contracts with the State of California for: (1) the wheeling, delivery, exchange, and storage of water through the facilities of the State Water Project of California for use in the Mid-Valley Unit; and (2) the construction or enlargement of conveyance and storage facilities for joint use.

Allows the Secretary to enter into agreements with the Mid-Valley Water Authority for the provision of the distribution facilities as the local contribution to the cost of the project.

Authorizes appropriations.