The largest irrigation district in the United States is bulking up on lawyer-lobbyists in Washington for a battle pitting agribusiness against an array of environmental groups.

Sidley Austin notified Congress this month that government-strategies counsel Catherine Karen is lobbying for the Fresno, Calif.-based Westlands Water District, becoming the fourth big-firm lobbyist in Washington to represent the irrigation district. She joined Brownstein Hyatt Farber Schreck shareholder David Bernhardt and of counsel Ryan Smith, as well as Akerman Senterfitt of counsel Joseph Findaro Jr., according to congressional records.