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12/9/2015
1
Field scale, edge-of-field monitoring of surface water quality in the lower mississippi river
basinMichele L. Reba, PhD, PE
USDA-Agricultural Research Service
Delta Water Management Research Unit
Outline
• Motivation
• MRBI Edge-of-field monitoring
• Related research studies
4.804 M ac
8.297 M ac
7.862 M ac
4.489 M ac
2012 Census
4.461 M ac
5.010 M ac
8.559 M ac
8.016 M ac
2007 Census
Arkansas
Texas
California
Nebraska
Alluvial Aquifer
• 2012 (Mgal/d)• Pumped: 8,036
• Sustainable Yield: 3,374
• Unmet Demand: 4,462
• Agriculture 98%
Source: Arkansas Natural Resources Commission 2015
Clark et al. (2011)
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Water Quality
• Excess Nutrients• Nitrogen
• Phosphorus
• Hypoxia• < 2 ppm DO
• Sparrow model• (Rebich et al., 2011)
• 32% N
• 50% P
Figure source: www.usepa.gov
Motivation
• Irrigation is key to reducing production variability
• Irrigate smarter
• Reduce inputs• Improve profit
• Reduce excess nutrients
• Challenge• Agro-economic
• Environmental
Mississippi River Basin Healthy watersheds Initiative (MRBI)
• 13 states
• Facilitate implementation of conservation practices• Avoid, control & trap
nutrient runoff• Maintain productivity
• Programs• Cooperative Conservation
Partnership Initiative (CCPI)• Wetlands Reserve
Enhancement Program (WREP)
• Arkansas
• Conservation Practices
Conservation Practices
• Monitoring
• Nutrient management
• Water management
• Irrigation management
• Cover crops
• Conservation tillage
• Grassed ways
• Riparian buffer
• Surface water storage
• Shallow water development for wildlife
Collaborators Statewide Network
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Study Sites Edge-of-Field Data Collection
• Velocity
• Depth
• Turbidity
• Water sample• Sediment
• Nutrients
• Event trigger
• Remote upload
Nutrient Analysis
• Sediment• TSS (APHA 2005 method 2540 D)• Suspended sediment cnc. (ASTM Method D3977-97)
• Nitrate• APHA (2005) method 4500-NO3-E • Cd reduction & analyzed as NO2 colorimetric reaction• MDL: 0.02 mg N/L, Range: 0.2 – 5 mg N/L
• Orthophosphate• APHA (2005) method 4500-P E • Ascorbic acid method• MDL: 0.01 mg/L, Range: 0.05 – 1.0 mg P/L
Little River Ditches MRBICaraway, AR
• Cotton
• One pair
• Two 75-acre
• Sandy Loam
Cover cropCase study
• 2011/2012 and 2012/2013 fallow season
• P & K Fall application (Oct)
• Plant cover crop wheat (Nov)
• Terminate cover crop • (3-4 weeks before planting, ~early
April)
• Plant cotton (early May)
• Nitrogen: liquid knife 120 units N per acre (early June)
• Harvest (October)
Photo Credit: Dr. Tina Gray Teague
0.0
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Dis
solv
ed P
O4
(mg/
L)
Event Date
Conservation
Conventional
Dissolved PO4
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Susp
ende
d Se
dim
ent C
once
ntat
ion
(g/L
)
Event Date
Conservation
Conventional
Suspended Sediment CNC
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P04 Dis Total P N03 Dis N02 Dis Total N
mg/
L
Conservation
Conventional
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30.0
P04 Dis Total P N03 Dis N02 Dis Total N Sediment
Conservation
Conventional
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Conservation P04 Conventional P04 Conservation N03 Conventional N03 Conservation N02 Conventional N02
mg/
L
NutrientsCaraway 2012 & 2013 Winter
0
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Conservation Sediment Conventional Sediment
g/ L
SedimentCaraway 2012 & 2013 Winter
• No statistical difference in any comparisons by t-test and Wilcoxon Rank-Sum test• Reduction in variability at conservation field
Cotton Study Sites2014
• Sandy Loam• Variable
• 38 acre field split
• Year 1 of 2 years of baseline
• 2012/2013 winter cover crops
• Practices• Oat cover crop (Nov)
• Oat terminated (April)
• Tillage-do all
• Liquid N 35 lb/ac, Broadcast N 110 lb/ac, KO2 41 lb/ac (June 19)
• Harvest (Oct 22)
• Terra Till
• Winter wheat cover crop (Nov)
• Sharkey Clay
• 3 field pair (40-acre)
• Year 1 of 2 years of baseline
• Rice/soybean rotation
• Practices• Pre-plant N 30 lb/ac• Tandom disk till• Pre-flood N 86 lb/ac• Harvest 190 lb/ac (XL 753)• Burn stubble
Rice Study Sites2014
Nutrients 2014
0.000
0.100
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0.700
DISSOLVED PO4(lb/ac)
TOTAL P (lb/ac) DISSOLVED NO3(lb/ac)
DISSOLVED NO2(lb/ac)
TOTAL N (lb/ac)
Loa
d (l
b/ac
)
COTTON-CONTROL COTTON-TREATMENT RICE-CONTROL
RICE-TREATMENT 1 RICE-TREATMENT 2
• No statistical difference in any comparisons for paired events by t-test and Wilcoxon Rank-Sum test • Sum of total N: 2 & 4.5% of applied N in rice (25 and 29 samples)
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Ghg reduction irrigation mngmt
Site
• 4 new MRBI sites
• Rice/soybean
• NE Arkansas
Alternate Wetting & Drying
• GHG benefit
• Reduce water use
• Sustain yield & milling quality
CEAP Watershed
In-stream Water Quality Study
• Monitor nutrients and sediments year round in-stream (drainage ditches).
• Validate model simulations of nutrients and sediment transport in irrigated agricultural land in the Little River Ditches (080202040804) and Lower St. Francis (080202031301) basin using both EOF and in-stream monitoring (ISM) data.
• Develop an improved understanding of nutrient and sediment transport, transformations and the hydrology in an irrigated landscape.
In-stream Water Quality Study
Little River Drainage Basin HUC 080202040804Approximately 10,000 acres (4047 Ha)Ditch no. 14-Buffalo Creek Ditch
Little River Ditches Basin
W1W9W5
W7
W3
Inlet ditchIn-stream stationsEOF stations
In-stream Water Quality Study
Lower St. Francis Basin HUC 080202031301Approximately 5,000 acres (2023 Ha)Ditch no. 1-St. Francis River
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M2 M8
M10
M6
Inlet ditchIn-stream stationsEOF stations
M4
Lower St. Francis Basin Instrumentation
Per watershed• 3 Isco autosamplers• 3 area-velocity sensors and modules• 2 trolls (water depth sensors)• 3 to 5 DS5X sondes• 2 OBS 500 sensors
× 2
Edge-of field (5)
Nutrients
Grab,eventLab
NO3, NO2, TN, TP, SP
Sediments
Grab, eventLab
SSC, TDS, TSS
ContinuousOBS300
Turbidity
Flow
ContinuousISCO
Rainfall, H, V, Q
In-stream (10)
Nutrients
Grab, weeklyLab
NO3, NO2, TN, TP, SP
ContinuousSonde
pH, NO3, NH4, DO, T
Sediments
Grab, weeklyLab
SSC, TDS, TSS
ContinuousSonde
TDS, Turbidity
Flow
ContinuousIsco
H, V, Q
ModelingAPEX, AnnAGNPS
Autosampler Area-velocity sensor
Sondedeployed in ditch
Laboratory calibration of sonde
monitoring Select Data: Turbidity and nitrate
Low
er S
t. F
ranc
is B
asin
0
10
20
30
4/6 5/6 6/5 7/5 8/4 9/3 10/3Nit
rate
, mg
N
/l
Date
DownstreamUpstream
Select Data: Nitrate (grab) and nitrate (15 min)
Grab samples
Sondemeasurement
Low
er S
t. F
ranc
is B
asin
0
1
2
3
4
4/6 5/6 6/5 7/5 8/4 9/3 10/3
Nit
rate
, mg
N
/L
Date
DownstreamMidstreamUpstream
Ceap effort
• Nearly 1 full year of data
• Modeling• AnnAGNPS
• APEX
• Sampling strategies• Grab
• Passive
• Continuous
• Biological analysis
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summary
• Edge-of-field measurements • Cover crops
• No statistical difference
• Baseline Year 1• No statistical difference• Off season spikes
• Additional analysis
• Long-term view
• State-wide network
• Future effort• Inform in-stream impacts• Co-benefits of management
Thank you
• Collaborators/Contributors• Nadine Straitt (funded through CIG-Daniels)
• Dr. Niroj Aryal (funded through CEAP watersheds)
• Delta Water Management Research Unit
• Arkansas State University• Dr. Tina Gray Teague
• Ecotoxicology Res. Lab
• Conservation Districts
• Producers
Michele L. Reba, PhD, PEResearch Hydrologist
USDA-ARSDelta Water Management Research Unit
