Heather Welles


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Heather Welles represents clients in complex litigation and transactions and provides regulatory and strategic advice, with a particular focus on water, land use, and public law and policy issues. She has drafted briefs in federal and state trial and appellate courts on a range of subjects, including multiple issues of first impression. Heather is a core member of the firm’s water practice, representing clients in a range of industries, including public agencies, agriculture, energy, private equity, and environmental conservation. She regularly speaks on water law and related issues. Heather also maintains an active pro bono practice focused on civil rights and impact litigation.

Prior to joining O’Melveny, Heather completed two federal appellate clerkships, most recently for the Honorable David S. Tatel on the DC Circuit Court of Appeals, and previously for the Honorable William A. Fletcher on the Ninth Circuit Court of Appeals.


Honors & Awards

  • Member of the team recognized as Environment/Natural Resources Litigation Firm of the Year by Benchmark Litigation California (2019)


Bar Admissions

  • California

Court Admissions

  • US Court of Appeals, Ninth Circuit
  • US District Court, Central District of California


  • University of California at Berkeley, J.D.: Thelen Marrin Prize for Academic Excellence (best academic record in graduating class); Order of the Coif; Editor in Chief, Ecology Law Quarterly; Landis Prize (most accomplished research paper in water or local government law); American Jurisprudence Awards for best exam in Constitutional Law, Contracts, Water Law, and Land Use Law
  • University of California at San Diego, B.A., Political Science 

Professional Activities


  • Honorable David S. Tatel, US Court of Appeals, District of Columbia Circuit
  • Honorable William A. Fletcher, US Court of Appeals, Ninth Circuit


  • “Toward a Management Doctrine for Texas Groundwater,” Ecology Law Quarterly, Vol. 40 (2013)
  • “What’s a Smelt Worth?: The Endangered Species Act and the Commerce Clause in the Bay-Delta,” Ecology Law Quarterly, Vol. 39 (2012)
  • “Will the Wilderness Act Be Diluted in Drakes Estero?” Ecology Law Quarterly Currents (Aug. 26, 2012) (co-authored with Nell Green Nylen, Elisabeth Long, Mary Loum, Dan Carlin, Brynn Cook, and Sage Adams)
  • Representing a public agency in federal court on multiple matters of first impression involving reserved water rights.
  • Serving as the primary drafter of appellate briefing defending O’Melveny’s successful challenge to a local initiative impacting property rights and water use. Co-authored trial briefing and presented argument in a regulatory takings bench trial and collateral administrative proceedings. The case resulted in a rare facial takings ruling in favor of O’Melveny’s client.
  • Advising a major energy company and a major utility company on federal constitutional and statutory issues related to international and interstate pipelines, including appellate briefing and strategy, consulting with federal officials, and regulatory advice.
  • Advising on water rights and legal issues affecting water supply in multiple contexts, including disputes, project development, and regulatory compliance.  Representative projects include multi-million-dollar transactions related to land acquisition and infrastructure.
  • Representing a nonprofit organization in connection with high-profile negotiations over water quality in the Sacramento/San Joaquin River Delta system.
  • Advising a government agency and nonprofit organization on constitutional, statutory, and regulatory issues related to immigration.
  • Representing Planned Parenthood Arizona and individual clinicians in impact litigation challenging numerous statutes that reduce access to reproductive health care.