Arizona Gov. Katie Hobbs has released a water modeling report showing that plans to add homes west of the White Tank Mountains will require other water sources to move forward. While the state’s groundwater law requires developers in the Phoenix area to get state certificates of assured water supplies extending out 100 years before they can build, Arizona Water Resources director Tom Buschatzke said he would not issue new certificates for the area unless developers find secure water sources in addition to the local groundwater.

The Howard Hughes Corp. is a major player in the area, with 100,000 homes planned on 37,000 acres.

The question of where developers might get the water to support such vast housing tracts has previously presented a mystery, with some developers merely saying they were confident in their prospects. The report the state released this week provides an initial answer: They won’t be finding that water solely in the aquifer below the land. Instead, they will have to find new ways of importing and possibly recycling water if they want to build out the property.