The McMullin Area Groundwater Sustainability Agency (MAGSA) is a Joint Powers Authority formed in January 2017 through the adoption of a Joint Powers Agreement (JPA) by the Mid-Valley Water District, Raisin City Water District, and County of Fresno. The JPA establishes that the MAGSA governing body shall be a five member Board of Directors, with each seat selected by the respective board of each member agency.
| Seat | Assignment |
| 1 | Raisin City Water District |
| 2 | Raisin City Water District |
| 3 | Mid-Valley Water District |
| 4 | County of Fresno |
| 5 | ‘White Area’ landowner appointed by the County of Fresno |