According to the U.S. Geological Survey – Estimated Use of Water in the United States in 2005 – there are 60 million irrigated acres across the nation using 144 million acre-feet of freshwater annually. Irrigation from groundwater accounts for 42 percent of this total, or 60 million acre-feet per year. This represents the largest consumptive use of groundwater: 67 percent of fresh groundwater withdrawals nationwide are for irrigation purposes. This illustrates the importance of accurate estimates of irrigation water use, and the need for adoption of best available science, technologies, and information sharing. Presentations will cover a broad spectrum of topics including remote sensing, evapotranspiration calculations, and collaborative efforts involved with a ground-up approach and offer a perspective on the various technologies and methods available to estimate irrigation water use and groundwater withdrawals for irrigation purposes.