Twenty-First Century Water Commission Act of 2003

Twenty-First Century Water Commission Act of 2003 - Establishes the Twenty-First Century Water Commission to: (1) use existing water assessments and conduct additional assessments necessary to project future water supply and demand; (2) study Federal, interstate, State, and local agency and private entity water management programs directed at increasing water supplies and improving the availability, reliability, and quality of freshwater resources; and (3) consult with representatives of such agencies and entities to develop recommendations consistent with laws, treaties, decrees, and interstate compacts for a comprehensive water strategy that respects the primary role of States in regulating water rights and uses, identifies incentives for ensuring an adequate and dependable supply of water to meet U.S. needs for the next 50 years, considers all available technologies for increasing water supply reliability while safeguarding the environment, suggests financing options, and suggests strategies to conserve existing water supplies.

Provides for the appointment of Commission members by the President and congressional leaders.

Requires the Commission to hold no fewer than ten hearings and to transmit interim reports and a final report to the President and specified congressional committees. Requires the Commission to terminate no later than 30 days after it transmits its final report.

Authorizes appropriations.