Hawaii Water Resources Act of 2003 - Amends the Reclamation Wastewater and Groundwater Study and Facilities Act to authorize the Secretary of the Interior to participate in the design, planning, and construction of: (1) a project in Kalaeloa, Hawaii, to desalinate and distribute seawater for direct potable use within the service area of the Board of Water Supply, City and County of Honolulu, Hawaii; (2) facilities in Kealakehe, Hawaii, for the treatment and distribution of recycled water and for environmental purposes within the County of Hawaii; and (3) and acquire land for, facilities in Lahaina, Hawaii, for the distribution of recycled water from the Lahaina Wastewater Reclamation Facility for nonpotable uses within the County of Maui. Limits the Federal share to 25 percent of the total cost of any such project. Prohibits the use of funds provided by the Secretary for project operation and maintenance.
Amends the Hawaii Water Resources Act of 2000 to: (1) increase the authorization of appropriations for the Federal share of activities authorized under the Act for the Hawaii Water Resources Study; and (2) eliminate the prohibition against the total Federal cost share for the study and reports from exceeding the amount authorized by the Act.