Water use in the West is changing, and nowhere is that being felt as acutely as the Imperial Irrigation District, a 450,000-acre, 12-month growing season district in Southern California where longstanding agricultural water users are under intense pressure to transfer water to the region's ever-thirsty and ever-expanding urban areas. In 2003, the District entered into 37 transfer agreements (IID, 2007), referred to collectively as the Quantification Settlement (QSA) and related agreements. The QSA committed the District to a massive efficiency conservation program that would up roughly 10 percent of its water for transfer to San Diego and others. The heart of the QSA calls for the District to generate more than 300,000 acre-feet of water through a combination of District and voluntary on-farm efficiency conservation savings. In 2007, IID completed their Efficiency Conservation Definite Plan (Definite Plan) that outlined strategies for both delivery system and on-farm water savings. The pertinent terms of the water transfer agreements and their implication to development of the Definite Plan are discussed and the elements of the Definite Plan are presented. The paper concludes with an assessment of lessons learned and discussion of key technical and other issues encountered.