Lower Rio Grande Valley Water Resources Conservation and Improvement Act of 2004

Lower Rio Grande Valley Water Resources Conservation and Improvement Act of 2004 - Amends the Lower Rio Grande Valley Water Resources Conservation and Improvement Act of 2000 to authorize specified additional projects, including projects for water conservation and improvement in Cameron, Hidalgo, Willacy, Hudspeth, and El Paso counties, Texas.

Permits each project that the Secretary of the Interior, acting through the Commissioner of the Bureau of Reclamation, conducts or participates in to include: (1) the replacement of irrigation canals and lateral canals with buried pipelines; (2) the impervious lining of irrigation canals and lateral canals; (3) the installation of water level, flow measurement, pump control, and telemetry systems; (4) the renovation and replacement of pumping plants; and (5) other activities that will result in water conservation or an improved water supply. Authorizes the Secretary to transfer and use for another such project up to ten percent of amounts made available for a project.

Reauthorizes appropriations for Lower Rio Grande construction.