Agricultural Water Consumption in the ACT/ACF River Basins: Approaches for Projecting Irrigated Acreage and Amounts

Abstract

Accurate assessment of current and future irrigation in the ACT/ACF river basins requires quantification of agricultural irrigation. Irrigated acreage is difficult to measure and project. No systematic monitoring of agricultural water application rates or irrigation volume occurs. Secondary sources must be combined with irrigation acreage estimates to derive irrigation water-use. Several sources and techniques available for determining irrigated acreage and water-use were compared. These approaches included surveys of farmers and experts, physical checks at random. locations, manual and computer analysis of remotely sensed images, crop models, and farmer-reported irrigation intentions. Four counties in Southwest Georgia with predominantly fixed irrigation systems were evaluated. There was good agreement among acres and irrigation volumes determined from surveys, physical checks, models, and image analysis. The four county total irrigation volume averaged 63.5 mgd for these approaches. The Comprehensive Basins Study and the DNR-EPD permitted irrigation volumes were higher than these four approaches by 65% and 160%, respectively. Where mobile irrigation systems are in use differences were greater. Each method has its flaws, gaps, and overlaps.