Magna Water District Water Reuse and Groundwater Recharge Act of 2008 - Amends the Reclamation Wastewater and Groundwater Study and Facilities Act to authorize the Secretary of the Interior, in cooperation with the Magna Water District, Utah, to participate in the design, planning, and construction of permanent facilities needed to establish recycled water distribution and wastewater treatment and reclamation facilities that will be used to provide recycled water in that District. Limits the federal share to 25% of the project's total cost.