Mapping the Spatio-Temporal Evolution of
Irrigation in the Coastal Plain of Georgia, USA
Marcus D. Williams, Christie M.S. Hawley, Marguerite Madden, and J. Marshall Shepherd
Abstract
This study maps the spatial and temporal evolution of acres
irrigated in the Coastal Plain of Georgia over a 38 year period.
The goal of this analysis is to create a time-series of irrigated
areas in the Coastal Plain of Georgia at a sub-county level.
From 1976 through 2013, Landsat images were obtained and
sampled at four year intervals to manually detect Center-Pivot
irrigation (
CPI
) systems in the analysis region. During the 38
year analysis period there was a 4,500 percent increase in
CPI
systems detected that corresponded to an approximate 2,000
percent increase in total acreage. The bulk of the total acreage
irrigated is contained in southwest Georgia, as seven coun-
ties in the region contained 38 percent of the total acreage
irrigated in 2013. There was substantial growth throughout
the entire Coastal Plain Region, but southwest Georgia was
identified as the most heavily irrigated region of the state.
Introduction
Agriculture has always been critical for sustaining human life
on Earth. Improving technology and agricultural practices
made it possible for world food production to double over a
31 year period between 1960 and 2000 (Tilman, 1999), which
is part of a larger increased agricultural production in the 20
th
Century known as the Green Revolution (Evenson and Gollin,
2003). In the year 2000, approximately 15 million square ki-
lometers of the global land cover was dominated by cropland
(Ramankutty
et al
., 2008). With the current world population
of 7.3 billion, which is expected to reach 11.2 billion by the
year 2100 (UN Department of Economics and Social Affairs)
and the growing demand for biofuel production (Evans, 2009)
the need for agricultural landscapes could potentially in-
crease in the future. One catalyst from the rapid improvement
of agricultural production was the large expansion of irriga-
tion (Tillman
et al
., 2001).
Irrigation can be defined as land areas that receive full
or partial application of water by artificial means to offset
periods of precipitation shortfalls during the growing peri-
od (Ozdogan
et al
., 2010). In 2000, it was estimated that 2.8
million km
2
were irrigated, with this number forecasted to
increase 5.29 million km
2
by 2050 (Tilman, 2001). Irrigation,
much like urbanization, acts to alter the natural landscape
properties such as partitioning latent and sensible heating at
the surface of the Earth which can impact surface temperature
and surface moisture transport. Understanding the extent and
usage of irrigation is imperative in answering questions about
future water resources, as it is estimated that irrigation uses
over 70 percent of the world’s consumption of freshwater
(Boucher, 2004; Velpuri
et al
., 2009). Irrigation accounts for
approximately 60 percent of consumptive use of freshwater
in the United States where estimates show that over 222,577
km
2
of cropland are irrigated (Braneon, 2014; Minchenkov,
2009).
For Georgia, it is estimated that approximately 5.5 billion
gallons of water per day were withdrawn from surface and
ground waters in 2004 (Barnes and Keyes, 2010). Agricultural
water use during 2005 totaled 752 million gallons per day for
irrigation, with the highest rate of irrigation occurring in the
Coastal Plain region of Georgia. The primary crops irrigated in
Georgia are maize, cotton and peanuts as they accounted for
approximately 68 percent of the total irrigated acreage in 2002
(Braneon and Georgakakos, 2014). Agricultural water use in
Georgia is also tied into the ongoing dispute between Georgia,
Florida, and Alabama over water use in the Apalachicola-Chat-
tahoochee-Flint (
ACF
) River Basins known as the “Tri-State”
waters wars. Georgia is the upstream water user and the heavy
agricultural water usage in southwest Georgia impacts the
amount of fresh water that reaches Apalachicola Bay in Florida
which supports a multi-million dollar shellfish industry.
Research has shown that irrigated croplands can impact
land-atmosphere interactions and fresh water supply. Various
modeling and observational studies have demonstrated that
irrigation influences climate at the local, regional, and global
level by enhancing evapotranspiration, altering precipitation
patterns, as well as impacting minimum temperature, maxi-
mum temperature, and diurnal temperature range (Barnston
and Schickedanz, 1984; Greets, 2002; Adegoke
et al
., 2003;
Boucher, 2004; Kueppers, 2007; Lobell and Bonfils, 2008;
DeAngelis
et al
., 2010; Sen Roy
et al
., 2011; Cook
et al
., 2014
Shukla
et al
., 2014, Williams
et al
., 2015) These activities
present a need for accurate and detailed geospatial informa-
tion on irrigated croplands (Pervez and Brown, 2010). In the
United States, most mapping efforts are focused primarily on
the California and the Great Plain regions.
To expand and contribute to existing knowledge on the spa-
tial and temporal changes in irrigation in Georgia, this analysis
maps center pivot irrigation systems (
CPI
systems) through
visual interpretation of Landsat satellite imagery. This shape-
based method of mapping irrigation is commonly done for
local scale mapping efforts.
CPI
systems are easy to identify in
Landsat imagery because of their distinct arc-like appearance.
Landsat was preferred for this analysis because of its greater
spatial coverage and the availability of imagery for more time
periods. In Georgia,
CPI
systems are used to irrigate multiple
crops, and an accurate estimate of the number of
CPI
systems
in the state could lead to better estimation of water use (Boken
et al
., 2004) and help identify potential climatic impacts. The
analysis herein is conducted on a regional scale, with a meth-
odology normally used for local scale studies. The goal was to
Marcus D. Williams and Christie M.S. Hawley are with the
USDA Forest Service, Southern Research Station, Center for
Forest Disturbance; 320 E. Green Street, Athens, GA 30602
(
).
Marguerite Madden and J. Marshall Shepherd are with the
University of Georgia, Department of Geography, 210 Field
St. No. 204, Athens, GA 30602.
Photogrammetric Engineering & Remote Sensing
Vol. 83, No. 1, January 2017, pp. 57–67.
0099-1112/17/57–67
© 2017 American Society for Photogrammetry
and Remote Sensing
doi: 10.14358/PERS.83.1.57
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
January 2017
57
