70th SWCS International Annual Conference July 26-29, 2015 Greensboro, NC

1. Simulating system-wide effects of
reducing irrigation withdrawals in the
Apalachicola-Chattahoochee-Flint (ACF)
river basin
By: Steve Leitman
July 2015

2. • about 20,000 sq mile
basin
•¾ basin in Georgia
•1/8 in Alabama and Florida
•median annual flow
about 16,000 cfs

3. Introduction
• For the past several decades water users and
managers in the ACF basin have been locked in
controversy over the use and management of the
watershed and this controversy has led to:
– the creation and subsequent termination of the first river
basin compact in the U.S. since passage of the major
environmental laws in the 1970s circa 2000.
– multiple lawsuits among the three states in the watershed
and the federal government ultimately leading to the State
of Florida filing a lawsuit in the U.S. Supreme Court against
the State of Georgia in 2014.

4. Introduction
• In this presentation I will investigate whether a
reduction in consumptive losses to stream flow in
the Flint River portion of the ACF watershed through
the large scale introduction of water-saving irrigation
devices and practices can have a substantive positive
effect on inflows to the Apalachicola River from the
watershed above Jim Woodruff Dam and thereby
help put an end to this long-term conflict?

5. Introduction
• A large majority of the irrigated acreage in the ACF
basin above Jim Woodruff Dam resides in Georgia. Of
this total acreage:
– 77% occurs in the Flint basin
– 21% in the Spring Creek basin
– 2% in the Chattahoochee basin

6. • about 20,000 sq mile
basin
•¾ basin in Georgia
•1/8 in Alabama and Florida
•median annual flow
about 16,000 cfs

7. Center Pivot irrigation sites in the
vicinity of Camilla, Georgia

8. Introduction
• Between 2007 and 2010
– about 65% of the irrigation water used in Georgia was
from groundwater sources
– 22.5% from surface water sources
– 6% from well-to-surface ponds
– 6.5% from unknown sources
• The source of irrigation water is important because
different sources have different effects on the
streamflow.

9. Introduction
• Surface water withdrawals have a one-to-one affect
on streamflow.
• Groundwater withdrawals are more complicated and
dependent upon:
– whether aquifer and stream are linked in terms of
hydrology
– the properties of the aquifer from which the irrigation well
takes the water
– Distance between irrigation well and the stream
– stage or elevation of the surface of the stream
– In summation, relationship is more like six-to-one.

10. Introduction
• Agricultural irrigation practices which could be
implemented in the ACF basin to reduce irrigation
water consumption include:
– agricultural best management practices such as sod-based
rotation (SBR) (50 to 75%)
– Low pressure drop nozzles (22.5%) and
– the use of high residue cover crops, conservation tillage
and soil moisture sensing (15%).

14. Methods
• To evaluate the effects of changing agricultural
irrigation demands on the ACF system, an existing
systems model of the basin developed in the STELLA
modeling platform was used.
• Model was run with current operating rules (RIOP)
and current volume of consumptive demands.
• Model was run under climate conditions in the
watershed from 1939 to 2008.

15. Methods
• Agricultural irrigation’s effects on streamflow were
increased by 25% (increased demands), held
constant (current demands), reduced by 25%
(moderate decrease), reduced by 50% (large
decrease) and reduced by 100% (rain-fed) to
represent alternative levels of adoption and
implementation of water saving approaches and
technologies.

16. Results
Modeled flow for the Flint River at Bainbridge, Georgia for 2007 - 2008 with
varying levels of agricultural irrigation (cubic meters per second)
0.0
50.0
100.0
150.0
200.0
250.0
300.0
1/1/2007 3/1/2007 5/1/2007 7/1/2007 9/1/2007 11/1/2007 1/1/2008 3/1/2008 5/1/2008 7/1/2008 9/1/2008 11/1/2008
Increased demands current demands moderate decrease largedecrease rain-fed
Flow(cubicmeterspersecond)
Date

17. Results
Modeled flow for the Jim Woodruff outflow to the Apalachicola River for 2007 –
2008 with varying levels of agricultural irrigation (cubic meters per second)
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1/1/2007 3/1/2007 5/1/2007 7/1/2007 9/1/2007 11/1/2007 1/1/2008 3/1/2008 5/1/2008 7/1/2008 9/1/2008 11/1/2008
Increased demands current demands moderate decrease largedecrease rain-fed
Flow(cubicmeterspersecond)
Date

18. • about 20,000 sq mile
basin
•¾ basin in Georgia
•1/8 in Alabama and Florida
•median annual flow
about 16,000 cfs

19. Results
Modeled elevations at Lake Lanier, West Point and W.F. George reservoirs for 2007
and 2008 with varying levels of agricultural irrigation (meters)
314.0
316.0
318.0
320.0
322.0
324.0
326.0
328.0
1/1/2007 4/1/2007 7/1/2007 10/1/2007 1/1/2008 4/1/2008 7/1/2008 10/1/2008
Increased Demands Current Demands Moderate decrease Large decrease Rain-fed
ELEVATION(METERS)
DATE
LAKE LANIER RESERVOIR
186.0
188.0
190.0
192.0
194.0
196.0
1/1/2007 4/1/2007 7/1/2007 10/1/2007 1/1/2008 4/1/2008 7/1/2008 10/1/2008
Increased demands Current demand Moderate decrease Large decrease Rain-fed
WEST POINT RESERVOIR
ELEVATION(METERS)
DATE
50.0
52.0
54.0
56.0
58.0
60.0
1/1/2007 4/1/2007 7/1/2007 10/1/2007 1/1/2008 4/1/2008 7/1/2008 10/1/2008
Increased demands Current demands Moderate decrease large decrease Rain-fed
W.F. GEORGE RESERVOIR
ELEVATION(METERS)
DATE

20. Results
Performance metric for floodplain inundation in the Apalachicola River from
varying levels of agricultural irrigation

21. Results
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
x 1.25 x 1.0 x0.75 x 0.5 x 0.0
Annualspawninghabitat(hectares)innundated2.4-6metersfor>=
30daysduringMar-May
Performance metrics for sturgeon habitat availability from varying levels of
agricultural irrigation

22. Results
Frequency of years that flow was below important threshold values and median
number of consecutive days flow was below important threshold values for mussel
habitat in the Apalachicola River from varying levels of agricultural irrigation.

23. Results
Comparison of the relative distribution of irrigation withdrawal’s effects on streamflow
and reservoir elevation for the period of record and in two drought years.
JWOUTFLOW RESERVOIRS JWOUTFLOW RESERVOIRS JWOUTFLOW RESERVOIRS
increaseinirrigation 90.4% 9.6% 36.8% 63.2% 67.4% 32.6%
moderatedecreaseinirrigation 63.2% 36.8% 27.5% 72.5% 44.1% 55.9%
largerdecreaseinirrigation 74.1% 25.9% 40.4% 59.6% 64.5% 35.5%
noirrigation 90.9% 9.1% 59.3% 40.7% 95.4% 4.6%
periodofrecord 2007 2008

24. Conclusions
• The results showed that decreasing the volume of
irrigation withdrawal can have non-intuitive effects
on the ACF basin because of the rules for
management of the storage reservoirs.
• Demand savings incurred upstream do not always
directly translate to elevated flows downstream.

25. Conclusions
• In the ACF basin there is not a water supply problem
in normal rainfall years, only during drought years.
• Results showed that in years when there is a lesser
need for support from the federal storage reservoirs,
nearly all of the water savings from decreasing the
effects of consumptive withdrawals for agricultural
irrigation in the Flint basin would translate into
increased flow in the Apalachicola River.

26. Conclusions
Modeled elevations at Lake Lanier, West Point and W.F. George reservoirs for 2005
and 2006 with varying levels of agricultural irrigation (meters)
314.0
316.0
318.0
320.0
322.0
324.0
326.0
328.0
1/1/2005 4/1/2005 7/1/2005 10/1/2005 1/1/2006 4/1/2006 7/1/2006 10/1/2006
Increased Demands Current Demands Moderate decrease Large decrease Rain-fed
ELEVATION(METERS)
DATE
LAKE LANIER RESERVOIR
186.0
188.0
190.0
192.0
194.0
196.0
1/1/2005 4/1/2005 7/1/2005 10/1/2005 1/1/2006 4/1/2006 7/1/2006 10/1/2006
Increased demands Current demand Moderate decrease Large decrease Rain-fed
WEST POINT RESERVOIR
ELEVATION(METERS)
DATE
50.0
52.0
54.0
56.0
58.0
60.0
1/1/2005 4/1/2005 7/1/2005 10/1/2005 1/1/2006 4/1/2006 7/1/2006 10/1/2006
Increased demands Current demands Moderate decrease large decrease Rain-fed
W.F. GEORGE RESERVOIR
ELEVATION(METERS)
DATE

27. Conclusions
• But in years when there is a larger need for
augmentation support from the federal storage
reservoirs, such as in drought years, a considerable
percentage of the water savings would translate into
higher elevations at the federal storage reservoirs
• In evaluating flow metrics used to translate flow
changes to environmental effects it was found that
changes to flow would occur at a time and rate
which could affect federally listed mussel species but
not sturgeon spawning or floodplain inundation.

28. Conclusions
• During drought years, under current reservoir
operating rules (RIOP), significant decreases in
agricultural irrigation withdrawals results in:
1) supplemental releases not being made from the
upstream storage reservoirs in the Chattahoochee basin
and consequently,
2) higher elevations especially at Lake Lanier as well as,
3) having some of the increased flow in the Flint basin
resulting in increased flow in the Apalachicola River.

29. Conclusions
• The results of this study show that adopting
alternative agricultural practices that reduce
irrigation water demands could have substantial
effects in the ACF basin.
• Based on ongoing research on agricultural irrigation
practices in the ACF basin at both the NFREC and the
Stripling Irrigation Park, it seems plausible that
irrigation demands could be decreased substantially
in the future if alternative practices are implemented
at a large scale.

30. Conclusions
• The extent of this effect is dependent on the level at
which these practices are implemented and whether
it is a normal year or a drought year.
• The findings from this study suggest it may be
beneficial to
– pursue means and policies that would implement water
saving agricultural practices,
– conduct a systematic review of reservoir operations and
management in order to share increased flow from
reduced consumptive extractions in a manner that is
understood and acceptable to basin constituents.

31. Conclusions
• If the intent is to remedy flow related problems in
the Apalachicola River and Bay during droughts
through reducing agricultural irrigation water use,
then the plan for managing the federal storage
reservoirs will have to be modified.
• The Corps of Engineers, Mobile District is in the
process of revising the Water Control Manual for the
basin at the present time.

32. Conclusions
• The obvious question is: What has to be done
to get broader implementation of
conservation practices such as sod-based
rotation?
• Questions?