8/12/2014

1

A Novel Test of Artificial Recharge in the Mississippi River Alluvial

Aquifer in Arkansas

Michele L. Reba, PhD, PEUSDA-ARS

Delta Water Management Research Unit

USDAPreserving water quality & availability for agriculture

in the Mississippi River Basin

Delta Water Management Research Unit

• Jonesboro, AR

• Arkansas State University

• 2011-Watershed Physical

Processes Unit

• 2014-stand alone unit

Arkansas4.5 million

Nebraska8.4 million

California7.3 million

Texas5.4 million

Water Quantity

Arkansas6.1 M acres farmed4.5 M acres irrigated

Alluvial Aquifer

• 2008 (Mgal/d)– Pumped: 7,022

– Sustainable Yield: 2,987

– Unmet Demand: 4,035

• Agriculture 96%

Source: Arkansas Natural Resources Commission 2011

Approaches Toward Sustainability

• Conservation

• Surface-water diversions

• Technology

• On-farm storage

• Artificial recharge

Potential Storage in Alluvial Aquifer

• Water removed from storage since pumping began: 1.5 trillion cubic ft (or 35 million acre ft)

• Equivalent water depth if applied over area of aquifer: 4 ft

• Years to refill this volume at a rate of 1,000 gallons per minute: 21,000 years

• Depletion is continuing

8/12/2014

2

• Recharge rate

• Cost (installation, equipment, energy, maintenance)

• Long-term performance

• Water-quality of recharge water

• Water-quality changes in aquifer

• Flow of recharged water within aquifer

Artificial Recharge Viability Issues Artificial Recharge in Arkansas

• 1960’s: USGS conducts artificial recharge study at Rice Experimental Station

• USGS concludes that recharge could be done at a finite percentage of pumping rate

• Major factors affecting recharge: – air entrainment

– sediment clogging

– chemistry

• Major deterrent: cost of water treatment

Background • Bryan Huber

– Where idea originated

– Benefits to be derived

– Potential sources of recharge water

– Earlier attempt at recharging aquifer

• Cotton Inc. Core Funding– Groundwater/surface water interaction

– Viability of surface water storage

Objectives

• Field test of viability of alluvial aquifer recharge with groundwater

• Quantify water quality of potential recharge sources

• Quantify efficacy of low-cost filtration techniques

Study Site

• Poinsett County

• Largest rice producing

• Groundwater decline

Description of Recharge Test

• Monitor water levels from 4 observation wells prior to, during, and after recharge

• Pump water from one well and recharge it in another well ½ mile away

• Monitor pumping rate

8/12/2014

3

Recharge Test (Phase 1)

• Pump from well 1

• Inject in well 2 (about ½ mile from pumped well)

• Monitor water levels before, during, and after water injection

• Monitor flow rate, turbidity, and water temperature

Pumping well

Recharge well

Flow meter

Turbidity sensor

Riser pipe

Test results

• Average recharge rate: 565 gallons per minute

• Water level rise after 3.8 days: 38 ft (well 2); 0.7 ft (well 2A)

• Head space remaining in recharge well: ~80 ft 47

57

67

77

87

97

1/13 1/14 1/15 1/16 1/17 1/18 1/19 1/20 1/21

Date

Wat

er lev

el a

bove

tran

sducer

in w

ell

2, f

eet

44

44.5

45

45.5

46

46.5

47

Wat

er

leve

l above

tra

nsd

uce

r in

wel

l 2A

, feet

Water level in well 2Water level in well 2A

8/12/2014

4

44

45

46

47

48

49

50

51

52

53

54

1/17 1/18 1/18 1/19 1/19 1/20 1/20 1/21 1/21

Date

Wat

er

lev

el a

bo

ve t

ran

sd

uce

r in

wel

l 2,

fee

t

Water level in well 2

Water level in well 2A

Slope of recovery curve inWell 2

Well 2

Well 2A

Well 2A Residual Water-Level Buildup

Well 2 Residual Water-Level Buildup

0

1

2

3

4

5

6

7

8

1 10 100 1000 10000

Time since recharge stopped, minutes

Res

idu

al w

ater

-lev

el r

ise,

fee

t

S= (2.5- 1.2) ft = 1.3 ft

T = 264 Q/S = 264 x 565 gpm/1.3 ft = 114,700 gpd/ft = 15,340 ft2/day

Test Summary

• Recharge well accepted water readily at average rate of 565 gallons per minute

• Maximum water level rise was 38 feet

• Water level rise at 330 feet was 0.7 ft after 3.8 days of injection

• Transmissivity estimate was comparable to values from tests in other wells

• Air entrainment not a large impediment to recharge

• Recharge rate could be increased substantially

Water Quality

• Expense of water treatment

• Wetlands

• Filtration

• Reservoir construction – 2000-2009: 111

– 2012: 30

– 2013: 54

Study Site

• 5 Ditch/Reservoirs

• Henry/Hilleman Silt loam

• Nutrients

• Sediment

70 ac1980s

140 ac1980s

40 ac2000s

40 ac2000s

70 ac2010s

8/12/2014

5

Preliminary Results• Statistically significant difference in means

p-value < 0.01– Phosphates,Turbidity, TS

• Median % Reductions: 15%-70%

• Generalizations– Size of ditch

– Seasonality

0.000

0.100

0.200

0.300

0.400

0.500

0.600

EDCBA

Tota

l S

oli

ds

(g/L

)

Site

Reservoir

Ditch

Filtration Test

Continued Effort

• Filtration testing

• Continued water quality sampling– Sediment

– Nutrients

– Metals

• Inventory of reservoirs

Acknowledgments

• Bryan Huber

• Cotton Inc.

• John Czarnecki(University of Arkansas-Little Rock)

• J.R. Rigby (USDA-ARS)

• Jerry Farris (Arkansas State University)

• Cart Well, Inc.

• Depth to water: ~120 ft.

• Average unsaturated thickness: ~70 ft.

• Assumed specific yield: 0.20

• Storage per acre: 14 acre-ft

• Area of Huber farm: 1400 acres

• Aquifer storage: 19,600 acre-ft

• Time needed to fill at 500 gpm: 24 years!

Aquifer Storage Potential