Agricultural Water Consumption in the ACF River Basin: Current Approaches for Quantifying Irrigation in Georgia

Abstract

In the Flint River portion of the Tri-state Apalachicola, Chattahoochee and Flint (ACF) Basin agricultural irrigation is the largest consumer of water; yet, there has been no previous reporting of irrigation withdrawal amounts or times. Effective and fair allocation requires an accurate assessment of current use and needs. Our objective was to project monthly water needs for most of Georgia's crops for wet, dry and normal years using crop growth and water use models and long-term weather records. For normal years, predicted irrigation agreed with the 10 in./yr used in ACF formulas; in dry years it was less than the formula's 18 in./yr. Time of withdrawal varied widely by crop, but no combination of crops would result in the monthly April to August distribution of 2, 17, 42, 25, 14% of total annual irrigation used as an initial basis for negotiations. Farmer supplied data showed an even wider range of irrigation periods than model predictions. Human factors that affect irrigation in ways unrelated to crop water-needs make prediction of irrigation water consumption more difficult. Projected monthly withdrawals for irrigation should be modified to reflect current and projected acreage and water needs by specific crops.