Using a Small Sub-sample to Project State-wide Agricultural Irrigation Water Use in 2000

Abstract

The Agricultural Water: Potential Use and Management Program in Georgia program (Ag. Water Pumping) began instrumenting and collecting agricultural water use data in 1999. As of October 2000, at least 407 permitted agricultural withdrawals, and more than 600 individual sites are in the monitoring program across the state of Georgia. This represents, however, just a small subset of the more than 19,000 permitted sites in the state. In order to scale-up this subset to represent an estimate of total statewide agricultural irrigation water, the already collected data of the Ag Water Pumping project were used to estimate monthly average use amounts per crop type. Then, based on agricultural statistics data, the total amount of irrigated acreage for each crop in the state was estimated. These two sets of estimates were combined to project the total amount of agricultural irrigation water for the whole state. An initial rough estimate, based on permit numbers of agricultural irrigators who have the capacity to pump or withdraw 4.4 1/sec (100,000 gallons/day) from either surface or ground water, showed that if there are 22,000 such sites in the state then water use would be 330,000 M gallons/year for the whole state or 1,012,425 Acre- ft/year. The value arrived at using the actually measured Ag Water Pumping subset and scaling up was 489,000 M gallons/year or 1,501,457 Acre-ft/year. It is encouraging that this initial analysis to scale-up refined data has given a total state water use amount which is not radically different from the extremely gross estimate based on the number of permits and their allotted flow rates. Further analysis and additional data are needed to provide a legitimate estimate of agricultural water use in the state of Georgia.