Irrigation in the Mississippi Delta: History and Future
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Transcript of Irrigation in the Mississippi Delta: History and Future
Irrigation in the Mississippi Delta: History and Future
Mississippi Delta (not the MS River Delta)
Lower Mississippi River Flood Plain Altered
Mississippi River Flood Plain prior to landscape modifications for agriculture
Land Characterization: Bottomland hardwood wetlands Annual flooding distributes
nutrient-rich matter Artesian conditions in underlying
alluvial aquifer
Logged, drained, channelizedLevees built
Land Characterization: > 80% Agriculture
Row crops Rice Aquaculture
Primary concerns for sustainability: Water Quality Water Availability
Arkansas
Louisiana Mississippi
Alluvial Aquifer
Agriculture / Irrigation 3rd most intensively
used aquifer in US in 2000
MS 2nd largest user behind AR
50-150 ft
Gravel/Sand
Alluvial extent
MS Alluvial aquifer Cone of Depression
0
1000
2000
3000
4000
5000
6000
7000
MRVA - TN MRVA - LA MRVA - MO MRVA - MSMRVA - AR
Estim
ated
With
draw
als i
n M
GD
2000 Estimated Withdrawals
Irrigation a Necessity Irrigation is necessary in the Delta to
reach optimum productivity› 28% of annual precipitation› 4 billion gallons per day
Flow in Delta streams is at or near baseflow during the growing season (May-August)› Unknown amount comprised of irrigation
return flow
The Bogue Phalia (a northwest MS River) at lowest flow in July 2009
Mississippi River Alluvial Aquifer
What are the results of irrigation on water availability?
Declining Water Levels
1/197
1
1/197
7
1/198
3
1/198
9
1/199
5
1/200
1
1/200
750
60
70
80
90
100
110
120
L0027 SUNFLOWER
Wat
er-le
vel a
ltitu
de ,
in fe
et a
bove
sea
leve
l
~1 ft per year decline
Storage and base flow loss
-3,500,000
-3,000,000
-2,500,000
-2,000,000
-1,500,000
-1,000,000
-500,000
0
0
20
40
60
80
100
120
140
160
1955 1958 1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009
CU
MU
LA
TIV
STO
RA
GE
LO
SS W
ITH
IN C
ON
E O
F D
EPR
ESS
ION
AR
EA
, IN
AC
RE
-FE
ET
DIS
CH
AR
GE
, IN
CU
BIC
FE
ET
PE
R S
EC
ON
D
Cumulative Estimated Storage Loss within cone of depression area (acre-ft)
Annual Minimum Daily Discharge of the Big Sunflower River at Sunflower Gage
Annual Minimum Daily Discharge of the Bogue Phalia River near Leland Gage
Why is groundwater important for aquatic ecosystems?
Groundwater/Surface-Water Exchange Benefits:› Sustains baseflow in streams› Bank storage dampens overall flood impacts› Streambank stabilization – supplies moisture
to riparian vegetation› Temperature regulation for aquatic biota› Supplies nutrients and inorganic ions to stream› Buffer the transport of contaminants through
the streambed interface
Stream/Aquifer in Connection Stream/Aquifer not in Connection
Losing Stream
Gaining Stream
-Increased flow in stream-Decreased deposition of fine sediments-NO3 concentrations in stream reduced-Stream recharges alluvial aquifer
-Decreased flow in stream-Increased deposition of fine sediments-NO3 concentrations in stream concentrated-What are the affects on recharge?
GW dilutes NO3 in stream
Anaerobic conditions in aquiferpromote denitrification Disconnected Stream
Why is groundwater important for aquatic ecosystems?
What are the results of irrigation on flow paths through the aquifer?
A Complex System
Recharge 0.307
Mississippi River0.011
Bluff Hills0.052
Underlying Units-0.022
Discharge to wells-2.19
Stream Leakage0.120
Water-Table Conditions in 2007
How have water-level declines changed the condition of the alluvial aquifer?
Mississippi
River-0.002
Bluff Hills0.035
Underlying Units0.095
Recharge 0.066
Stream Leakage-0.192
Confined Conditions in 1870 (Predevelopment)
What are the Effects of Conservation (Management) on these Flow Paths in the Future?
Objectives Employ existing regional flow model to
assess future groundwater supply Develop water use conservation
scenarios that vary in amount and distribution
Assess the effects of amount and location of water use conservation
How will flow in the alluvial change in the future?
MS Delta Conservation Scenarios, 2010 - 2038
Water-Use
Reduction (%)
Delta WideCone of depression
areaConservation Location
0
10
20
30
40
50
60
5% Delta-wide
25% Delta-wide
5% Cone equiva-lent
25% Cone equiva-lent
Cone of Depression Area (approx. extent)
Change in Storage
5% Delta Wide5% Cone Equiva-
lent 25% Delta Wide25% Cone Equivalent
0%
5%
10%
15%
20%
25%
30%
35%
5% 6%
29% 32
%
Perc
ent I
ncre
ase
in S
tora
ge R
elat
ive
to B
ase
scen
ario
Base Flow
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160%
5%
10%
15%
20%
25%
25%Delta-wide 5% Delta-wide25% Cone Equivalent 5% Cone Equivalent
Stress Period (2008-2038)
Perc
ent i
ncre
ase
in b
ase
flow
rela
tive
to
base
sce
nario
How Can We Better Monitor Water Resources?
Real-time coupled groundwater streamgaging stations• Study Objective
• Assess the role of groundwater/surface-water exchange on the transport of nutrients in the northwestern MS
• Assess the feasibility of monitoring groundwater/surface-water exchange at existing streamgaging locations
• Near-stream piezometers installed July 2010 near existing stream gages• Big Sunflower at Clarksdale• Big Sunflower at Sunflower• Big Sunflower at Anguilla
Pressure Transducer: Head Conductance,
and Temperature
41.5’
EastWest
~100’
*not to scale
Deck for access during high
flow
Existing Gage House: Stage , Conductance, and Stream Temperature
DCP to relay transducer
data
Big Sunflower at Sunflower coupled groundwater/surface-water gage
Losing Conditions:Groundwater Level < Stream Stage
Pressure Transducer: Head Conductance,
and Temperature
41.5’
EastWest
~100’
*not to scale
Deck for access during high
flow
Existing Gage House: Stage , Conductance, and Stream Temperature
DCP to relay transducer data
85
90
95
100
105
110
115
Stag
e an
d G
roun
dwat
er L
evel
, in
ft ab
v m
sl
Big Sunflower at Sunflower, MSStageGroundwater Level in near-streampiezometerStreambed Surface
Affects of unsustainable groundwater withdrawals on the MS Delta
Loss of baseflow to streams› Groundwater is pumped into streams to
sustain flow - cost $$ and could exacerbate current water situation
› During the growing season, irrigation return flow can make up most of the water in streams
› Overuse of surface-water for irrigation has resulted in recent fish kills
Affects of unsustainable groundwater withdrawals on the MS Delta
Increased recharge from the surface› Increases the vulnerability of the aquifer to
surface contamination› Recharge is still not sufficient to replace
withdrawals
Affects of unsustainable groundwater withdrawals on the MS Delta
Future concerns over water supply for irrigation› State initiated Conjunctive Water Use task
force› Dissension over who actually is part of the
problem – within the cone of depression versus outside of the cone of depression
› Amount of irrigated acreage increasing each year along with new permits for groundwater and surface-water irrigation
Questions?