Subdividing Land in La Paz County, Arizona

Outside an AMA, the water-report rule applies to every subdivision -- not just six-plus lots

Inside an Arizona Active Management Area, a developer only needs to demonstrate a 100-year Assured Water Supply once a project reaches six or more lots. La Paz County has no AMA anywhere within it, so that six-lot trigger doesn't apply -- but a separate statute, A.R.S. § 45-108, fills the gap with a rule that's actually broader: outside an AMA, a developer of a proposed subdivision, including a dry-lot subdivision, must submit water-supply plans to ADWR's Director and demonstrate an adequate water supply before recording the plat, regardless of the number of lots. "Adequate" under this statute means the same substantive 100-year standard used inside AMAs -- water that will be continuously, legally, and physically available to meet the subdivision's needs for a century -- evaluated by ADWR rather than certified as an AMA-style guarantee.

The process itself has real procedural steps: once an application is administratively complete, ADWR publishes notice, and residents or landowners within the same groundwater basin have fifteen days after the last publication to file a written objection limited to whether the statutory adequacy criteria are met. In contested cases, or whenever the Director thinks one is warranted, an administrative hearing can be held before a final decision -- meaning a subdivision application here can, in principle, draw formal public objection from neighboring landowners in a way an AMA-area project's Certificate of Assured Water Supply generally does not.

What happens when the finding comes back "inadequate"

If ADWR's Director determines the proposed water supply is inadequate, the statute doesn't block the subdivision outright -- but it does force real, ongoing disclosure. The Director issues a water report stating the supply is inadequate and forwards it to the state Real Estate Commissioner and to the county responsible for platting. If the county still approves the plat, it must note the inadequate-supply determination directly on the face of the recorded plat -- a permanent, title-level flag -- and the developer must disclose the inadequacy both in the subdivision's official public report and in any promotional or advertising material shown to potential first purchasers. That disclosure obligation runs with the original sale of each lot, not with every later resale, so a buyer purchasing directly from the original developer is the party the law is most clearly designed to protect.

This is where the hub's McMullen Valley and Butler Valley findings stop being background and become a live subdivision-planning risk: ADWR's own 2023 Supply and Demand Assessment documented the McMullen Valley Basin's available water supply falling roughly three-quarters since 1990, with the basin projected to lose about five acre-feet for every one entering it, plus measured land subsidence -- exactly the kind of documented, basin-wide stress that makes an "inadequate" finding a realistic outcome for a new subdivision application near either basin, not a hypothetical worst case.

What this looks like in practice: an 8-lot subdivision in Sabola

In July 2025, the La Paz County Board of Supervisors approved a tentative plat for an eight-lot residential subdivision on a 40-acre parcel in Sabola -- a project that had been working through the county's process for several years. Two things from that approval are instructive for anyone platting land in the county today: the board required parcel-size adjustments so each of the eight lots met the applicable zoning district's five-acre minimum before final approval, and water availability for the project was specifically raised and discussed at the public hearing, with assurances given that sufficient water resources existed before the board moved forward. Neither the minimum-lot-size check nor the water-availability discussion was a rubber stamp -- both were live points of board scrutiny on a project of this modest size, underscoring that the ARS 45-108 water-report requirement and the county's own zoning minimums are both real, applied gates here, not boxes checked automatically.

What to actually check before subdividing or buying a lot in a new subdivision

1. Confirm with Community Development which of the county's zoning districts applies to your parcel and its specific minimum lot size -- the Sabola project needed lot-line adjustments to meet a five-acre minimum before the county would approve it.
2. Before platting any size subdivision, contact ADWR directly about the ARS 45-108 water-report process -- there is no lot-count exemption outside an AMA, unlike the six-lot AMA threshold covered on the state hub.
3. If you're buying a lot directly from a subdivision's original developer, ask to see the subdivision's public report and confirm whether an inadequate-water-supply notation appears on the recorded plat -- this is a title-level fact, not something a listing description will necessarily surface.
4. For land anywhere near the McMullen Valley or Butler Valley basins specifically, treat an ADWR adequacy finding as a real, live risk given the basins' own documented supply decline, not a formality -- budget time and cost for the water-report process into any subdivision timeline.
5. If a written objection period is open on a pending subdivision application in your basin, that's a signal worth investigating directly with ADWR before assuming the project's water plan is uncontested.