This document summarizes a study analyzing historical agroenvironmental conditions in the Lower Mississippi River Basin. The study examined long-term trends in natural resources and the environmental impacts of agriculture using data on land use, precipitation, hydrology, and water quality. The researchers found evidence that intensive groundwater irrigation in agricultural watersheds has altered surface water flows, reducing base flows and increasing low flow events, compared to non-agricultural watersheds. While more analysis is needed, the results suggest tradeoffs between agricultural productivity and hydrologic alteration may need to be considered for sustainable management in the region.

1. Historical Analysis of
Agroenvironmental Conditions in
the Lower Mississippi River Basin
Lindsey Yasarer, Jason Taylor, J.R. Rigby, Martin Locke
USDA-ARS, National Sedimentation Laboratory, Oxford, MS

2. USDA-ARS Long-Term Agroecosystem
Research (LTAR) Network
Partnership among 18 long-term
research sites across the US.
Vision for LTAR Network:
“Transdisciplinary science conducted
over decades on the land in different
regions, geographically scalable,
enhancing the sustainability of agro-
ecosystem goods and services.”
(Walbridge and Shafer, 2011)
Lower Mississippi River Basin LTARhttp://www.tucson.ars.ag.gov/ltar/

3. LTAR Research Questions
1. What factors drive agricultural productivity and its environmental impacts?
2. What are the tradeoffs between productivity, quality, societal preferences, and
ecosystem services?
3. What are the barriers to sustainable intensification?
4. How do we better target our use of resources?
5. What technologies and management strategies are needed for agriculture to be
resilient to extreme events (e.g., weather, disease outbreaks, pest infestations)?
6. What scientific synthesis products are needed for decision making?
http://www.tucson.ars.ag.gov/ltar/

4. Ecosystem Services and Agriculture
Services provided by
agriculture beyond
food, fuel and fiber
Potential disservices
caused by intensive
cropland management
Foley et al. 2005. Global Consequences of Land Use. Science 309, 570.

5. Lower Mississippi River
Basin LTAR
• HUC 2 watershed
• Two dominant ecoregions
o Southeastern USA Plains
o Mississippi Alluvial and Southeast USA
Coastal Plains

6. Study the past if you want to define the future
~ Confucious
Study Goals:
1. Examine long-term trends in natural resources and environmental impacts of
managed agricultural systems
2. Evaluate historical data available in the LMRB to elucidate trends
o Agricultural census data
o Land-use records and geospatial datasets
o Precipitation records
o Hydrology and water quality data

7. Land-use in LMRB
2008 -2016
0
10000
20000
30000
40000
50000
60000
70000
80000
Corn
Cotton
Rice
Sorghum
Soybeans
WinterWheat
OtherCrops
Fallow/Idle
ForestAll
Var.Aquatic
Developed
Grass/Pasture
Shrubland
Area(km2)
2008 2016
Data from USDA Cropland Data Layers:
2008, 2012, 2016
+34%
+12%
-23%
-47%

8. Management Trend: Increase in irrigated
land-use
PERMITTED WATER USE LOCATIONS, MS GROUNDWATER USE IN ARKANSAS
COUNTY
Of 3,000,000 acres farmed, 2,000,000 are irrigated in
Delta (YMD)
USGS (2002)

9. Dominant Water Resource:
Mississippi River Valley Alluvial Aquifer
• Withdrawals of 9290 Million gallons per day
mainly for irrigation
•Ranked 3rd in the nation of total withdrawals
Maupin and Barber. 2000. Estimated Withdrawals from Principal Aquifers in the United States. USGS Circular 1279

10. Research Questions & Preliminary Methods
RESEARCH QUESTIONS
o Is there significant hydrologic
alteration detected at LMRB long-
term hydrologic gauges?
o How does degree of hydrologic
alteration vary between agricultural
and non-agricultural watersheds?
METHOD
o Use Indicators of Hydrologic
Alteration (IHA) software to
evaluate trends using both a time
series analysis and a change point
analysis (1990)

11. Indicators of Hydrologic Alteration (IHA)
o Developed by The Nature Conservancy (version 7.1)
o Examine hydrologic impacts of human activities; develop
environmental flow recommendations; analyze scenarios
o Requires at least 20 years of daily hydrologic data
o Calculates 67 ecologically-relevant statistical parameters
- IHA parameters
- Environmental Flow Component parameters
In this study:
o Base flow index: 7-day minimum flow/mean flow for year
o Extreme Low Flows (frequency)
o Minimum (1-day, 3-day, 7-day)

12. Study Sites
Watershed Study Sites

13. Tennessee Watersheds
Agricultural Watershed:
• Loosahatchie River at
Arlington:
• 25% Row crop
• 38% Forest/Shrub
• 25% Pasture/Grass
Non-Agricultural Watershed:
• Hatchie River at Bolivar:
• 6% Row crop
• 64% Forest/Shrub
• 14% Pasture/Grass

14. HATCHIE RIVER LOOSAHATCHIE RIVER
Base Flow Index 1969 -2016 (1990 Breakpoint)
Upland Non-agricultural Upland Agricultural

15. HATCHIE RIVER LOOSAHATCHIE RIVER
Base Flow Index 1969 -2016
p=0.5
r2 = 0.0008
Slope = 0
p=0.5
r2 = 0.004
Slope = 0
Upland Non-agricultural Upland Agricultural

16. HATCHIE RIVER LOOSAHATCHIE RIVER
Frequency of Extreme Low Flows
p=0.5
r2 = 0.007
Slope = 0.0152
p=0.025
r2 = 0.13
Slope = -0.124
Upland Non-agricultural Upland Agricultural

17. Arkansas Watersheds
Agricultural Watersheds:
• Cache River at Egypt
• 69% Row Crop
• 15% Forest/Shrub
• L’Anguille River near Colt
• 70% Row Crop
Non-Agricultural Watersheds:
• Saline River near Rye
• 0% Row Crop
• 73% Forest/Shrub
• Ouachita River at Camden
• 0% Row Crop
• 74% Forest/Shrub

18. Base Flow
Index
1969 -2016
1990
Breakpoint
Arkansas
SALINE RIVER
OUACHITA RIVER
CACHE RIVER
LANGUILLE RIVER
Upland Non-agricultural Lowland agricultural

19. Base Flow Index 1969-2016
SALINE RIVER CACHE RIVER
UplandNon-agricultural Lowlandagricultural
p=0.5
r2 = 0.038
Slope = -0.0003
p=0.001
r2 = 0.42
Slope = -0.0012

20. Frequency of Extreme Low Flows
SALINE RIVER CACHE RIVER
Upland Non-agricultural Lowland agricultural
p=0.25
r2 = 0.062
Slope = 0.07
p=0.001
r2 = 0.36
Slope = 0.14

21. Louisiana Watersheds
Agricultural Watersheds:
• Boeuf River near Girard
• 68% Row Crop
• 13% Other Cropland
• Tensas River at Tendal
• 76% Row Crop
• 12% Water/Wetland
Non-Agricultural Watersheds:
• Comite River near Comite
• 1% Cropland
• 34% Water/Wetland
• 30% Pasture/Grass
• 29% Forest/Shrub
• Amite River near Denham
Springs
• 0% Cropland
• 46% Forest/Shrub
• 27% Water/Wetland

22. Base Flow
Index
1969 -2016
1990
Breakpoint
Louisiana
Upland Non-agricultural Lowland agricultural
AMITE RIVER
COMITE RIVER TENSAS RIVER
BOEUF RIVER

23. Base Flow Index 1969-2016
Upland Non-agricultural Lowland agricultural
p=0.5
r2 = 0.0069
Slope = 0.0004
p=0.001
r2 = 0.51
Slope = -0.0008
COMITE RIVER TENSAS RIVER

24. Frequency of Extreme Low Flows
Upland Non-agricultural Lowland agricultural
p=0.5
r2 = 0.0002
Slope = 0.0045
p=0.05
r2 = 0.09
Slope = 0.06
TENSAS RIVERCOMITE RIVER

25. Overview of Time Series Analysis 1969-2016
State Site Name Base
flow
Frequency
Extreme
Low Flows
TN Hatchie NS NS
AR Saline NS NS
AR Ouachita NS NS
LA Amite NS p=0.025
LA Comite NS NS
State Site Name Base
flow
Frequency
Extreme
Low Flows
TN Loosahatchie* NS
p=0.025
AR Cache
p=0.001 p=0.001
AR Languille
p=0.05
NS
LA Boeuf
p=0.001 p=0.001
LA Tensas
p=0.001 p=0.05
UplandNon-agriculturalWatersheds LowlandAgriculturalWatersheds
* Located in uplands with only 25% agriculture

26. Conclusions
 Evidence of hydrologic alteration related to base flow and low flow events in
lowland agricultural watersheds
 We hypothesize that intensive use of groundwater for irrigation in agricultural
watersheds has altered flow patterns in surface water systems; however, more careful
analysis of water use data is necessary.
Further exploration needed:
 Tradeoffs? Ecosystem services vs. hydrologic alteration
 Ecological impacts of hydrologic alteration
Lindsey Yasarer
Research Hydrologist
National Sedimentation Laboratory
USDA-ARS Oxford, MS
Lindsey.Yasarer@ars.usda.gov