Irrigation and Certificate of Use Compliance in the Wiregrass Region of Alabama

Abstract

Alabama passed the Water Resources Act of 1993 that included a Certificate of Use (CoU) program for users that have the capacity to withdraw 100,000 gallons per day or more. However, there is concern that some irrigation users do not apply for a CoU for various reasons. The primary focus of this study is on center pivot (CP) irrigation systems used for crop production; but other types of irrigation (e.g., golf courses, turfgrass farms, greenhouses) will also be considered. The objectives of the study are 1) to estimate CoU compliance for irrigation users in each sector and 2) to estimate water use for each agricultural sector from monthly reports provided by the CoU holders. Center pivot irrigation systems were visually identified on NAIP imagery for 2011, 2013, and 2015. Landowner data (owner name, mailing address, and parcel size) were linked to each CP by utilizing the online GIS portals of the counties in the study area. Certificate of Use holder data were then linked to the appropriate CPs for computing the compliance rate. The number of CPs for crop production increased each year: 2011 (425), 2013 (533), and 2015 (638); however, CoU compliance rate decreased each year from 27.5% in 2011 to 24.8% in 2013 to 22.7% in 2015. Approximately 49.1% of CP CoU holders submitted monthly withdrawal reports over the three years being investigated. These data were used to compute the reported amount withdrawn each year, and to estimate the unreported amount and total amount. A major decline in withdrawals in 2013 and increased withdrawals again in 2015 was likely related to variations in precipitation.