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 and public law and policy issues. She has drafted briefs in federal and state trial and appellate courts, including the US Supreme Court, on a range of subjects, including federal constitutional law, federal courts and jurisdictional issues, statutory interpretation, water law, contracts, and trademark law. Heather is a core member of the firm’s water practice, representing clients in areas 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 served as a law clerk for the Honorable David S. Tatel on the DC Circuit Court of Appeals and the Honorable William A. Fletcher on the Ninth Circuit Court of Appeals.

Heather graduated from the University of California, Berkeley School of Law, where she was awarded the Thelen Marrin Prize for Academic Excellence for graduating first in her class and served as the Editor in Chief of the Ecology Law Quarterly. She previously served as a legislative director in the Texas House of Representatives, where she worked on groundwater regulation, water quality, energy, and land use.


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, including successfully obtaining dismissal of multiple claims on standing grounds.
  • Representing coalition of large landowners in the first groundwater adjudication under California’s modified statutory adjudication scheme.
  • Co-authored appellate briefing in a California Court of Appeal case involving administrative res judicata and Coastal Commission enforcement authority.
  • Co-authored appellate briefing defending a successful challenge to a local initiative impacting property rights and water use. Co-authored trial briefing on regulatory takings and California constitutional issues and presented argument at trial and in collateral administrative proceedings.
  • Advised 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.
  • Co-authored successful pre-trial and post-trial briefing in a contract and trademark dispute involving more than $150m in potential liability.
  • Advising on water rights and legal issues affecting water supply in multiple contexts, including disputes, major transactions, project development, and regulatory compliance. Representative projects include multi-million-dollar transactions related to land and water rights acquisition and infrastructure development.
  • Represented a nonprofit organization in connection with high-profile negotiations over water quality in the Sacramento/San Joaquin River Delta system.
  • Advised a government agency and nonprofit organization on constitutional, statutory, and regulatory issues related to immigration.
  • Co-authored amicus brief on behalf of anti-violence organizations before the US Supreme Court in defending a Sixth Circuit decision holding that transgender Americans are protected by Title VII’s prohibition on discrimination on the basis of sex.
  • Co-authored appellate briefing in multiple Ninth Circuit cases involving the Board of Immigration Appeals.
  • Representing Planned Parenthood Arizona and individual clinicians in litigation challenging statutes that reduce access to reproductive health care.