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Panel split over bill that would change how ADWR counts stormwater recharge in groundwater models
Summary
House Bill 22‑70 would require the Arizona Department of Water Resources to update active management area groundwater models to assume some stormwater recharge from development offsets groundwater use; the committee advanced the bill amid opposition from water providers and ADWR.
House Bill 22‑70 would require the director of the Arizona Department of Water Resources (ADWR) to adopt rules and annually update active management area groundwater models to account for new natural, incidental or artificial stormwater recharge associated with development. The bill also would direct ADWR to assume that stormwater recharge generated by new or existing infrastructure offsets part of future groundwater use.
The Department of Water Resources testified neutral and flagged implementation challenges, saying ADWR already uses industry‑standard methods to estimate recharge rates and that accurately tracking incidental stormwater recharge attributable to specific development could be complex and resource intensive. “What you're asking us to do is take a shovel full and count each individual sand,” said a department representative describing the difficulty of micro‑measuring recharge.
The Arizona Municipal Water Users Association opposed the bill, arguing that models already account for incidental recharge and that adding new assumed recharge risks double‑counting. Barry Aarons of AMWUA urged waiting for ongoing research by university teams identifying locations and methods to protect and enhance recharge before changing law.
Rural Arizona Action’s Tom Prezelski said any additional stormwater recharge from development would be minimal and variable, and cautioned that in some communities recharge may be undesirable for flood control or public‑health reasons. Supporters of the bill (sponsor testimony was presented by committee staff) argued it would improve planning and account for emerging recharge opportunities associated with infrastructure.
The committee voted to give HB 22‑70 a due‑pass recommendation on a 5‑3 vote after debate. Several witnesses and members urged caution and asked ADWR to weigh implementation feasibility and the risk of overestimating future supplies.
Why it matters: Counting incidental or engineered stormwater recharge differently in groundwater models could affect water‑availability assessments used to permit development and to allocate groundwater rights in active management areas. Over‑ or under‑counting recharge has direct implications for long‑term water planning in a state with constrained groundwater supplies.
What’s next: If the bill advances, ADWR would need to develop rulemaking guidance and methods for quantifying stormwater recharge tied to development; the department and stakeholders discussed the need for research and standardized methodologies before broad adoption.
