Gov. Gavin Newsom signed two bills by Assemblymember Diane Papan requiring data centers to disclose their water use, a reversal after he vetoed a similar measure last year.

Papan, a Democrat who represents Burlingame, Hillsborough and surrounding San Mateo County communities in the state Assembly, has pushed for data center water transparency for two years. She also chairs the Assembly Water Committee.

The bills, Assembly Bill 2469 and Assembly Bill 2619, take effect Jan. 1, 2027. Newsom signed them Monday, Sept. 21, as part of a seven-bill data center regulatory package that his office described as the most comprehensive data center legislation in the country.

Newsom vetoed Papan's earlier version, AB 93, last year. In his veto statement, he said he was "reluctant to impose rigid reporting requirements … without understanding the full impact on businesses and the consumers of their technology," The Register reported.

This time, the governor signed.

AB 2469 requires data center developers to complete a water supply assessment and develop a water scarcity plan before a local government can approve a project, according to Papan's office. The bill also requires data centers to pay for any new water infrastructure their operations need, shielding local ratepayers from those costs.

AB 2619 uses the existing business license process to track water consumption. A data center company must disclose its projected water demand when applying for a license and report actual annual water use at each renewal, under penalty of perjury, according to CalMatters reporting in the Almanac.

Papan said in a statement that water management depends on measurement, Utility Dive reported. In an Aug. 31 interview with CalMatters, before the signing, she described her legislative strategy: "The main goal has been transparency. Let me give you the data, and let's go from there … I just didn't want anything to divert from that main goal."

The signing comes as public concern over data centers has grown across California. A Public Policy Institute of California survey in July found that a majority of residents oppose data center construction in their areas and worry about environmental impacts. California has 296 data centers, the third-highest total in the country, according to Data Center Map.

Newsom said in a statement that communities bear the consequences of data center growth, including higher electricity demand, grid constraints, water use and pollution. He said the new laws ensure Californians maintain control over proposed projects.

Supporters of Papan's bills include environmental groups and the Santa Clara Valley Water District. Opponents include the Data Center Coalition, the League of California Cities and the California State Association of Counties.

Both laws take effect Jan. 1, 2027, and will apply to any data center seeking local permits or business licenses in Burlingame, Hillsborough and cities across California after that date.