investigations of playa basins as point source...

Playas and High Plains Recharge; [email protected] Rainwater Basin Joint Venture 2017

INVESTIGATIONS OF PLAYA BASINS AS POINT SOURCE RECHARGE TO THE HIGH

PLAINS AQUIFER

Randy L. STOTLER1, Kait SALLEY1, William C. JOHNSON2, Dakota J. BURT2, and Mark W. BOWEN3

1 Department of Geology, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045

2 Department of Geography and Atmospheric Science, University of Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045

3 Geography and Urban Planning, University of Wisconsin Oshkosh, 800 Algoma Blvd, Oshkosh, WI 54901



Introduction

• High Plains (Ogallala) aquifer and Playas

• Types of recharge

– Diffuse

– Focused

• Timing of recharge

– Environmental tracers

– Agricultural contaminants


Buried playa (Kearny County)

“buffalo wallow” (Haskell County)

>22,000 playas in Kansas



4

From USGS Circular 1333

Note: Sandhills lakes not included in this assessment


Portals to the High Plains Aquifer?


Goal of this phase of playa research is one of determining if playas indeed serve as point sources for recharge of the High Plains Aquifer (in Kansas)

Approaches Vadose zone geochemistry and other proxies of water flux Groundwater modeling Surface water balance analyses Related issues, e.g., accelerated sedimentation of playa basins


Ehmke Playa


Temporal and Spatial Changes


Playa instrumentation


Tower array (recording every 10 minutes)

Wind velocity and direction Temperature and humidity Solar radiation (pyranometer) Rain Radiation (net) Surface water level (acoustic) Still and video imagery

Sub-surface sensors (upper 3 m)

Soil heat flux (thermocouples and heat flux plates) Temperature, EC, water content Water potential sensors


Instrumented pit profile characterization

0

50

100

150

200

250

0 50 100

L*

0 1 2 3

a*

0 5 10 15

b*

AMS 14C ages (cal yrs BP)

3320 ± 30

3835 ± 30

4145 ± 30

5300 ± 30


Dust collection


Drone-based monitoring


What about accelerated sedimentation?


Vegetation Buffers

Courtesy of Dave Haukos KSU

Sedimentation and playa function?


210Pb sediment dating half life = 22.2 years atmospheric deposition

Full-core analyses: Color imagery Geochemistry (XRF) Magnetic susceptibility Gray-scale imagery L*a*b* and Munsell colors Micromorphology Particle size distribution Stable isotopes

Crack filling?


Chemical tracers: Chloride Bromide Nitrate Isotope analyses: δ2H and δ18O, 3H

(wet and dry atmospheric fallout)

(precipitation and plant-soil interactions)

Vadose Zone Geochemistry

(groundwater source and age)


Vadose Zone

Core is sealed in the field, and returned to the lab for fluid extraction


Sample Preparation


PROJECT STATUS

1. Instrument station active

2. Waiting for sufficient rainfall to inundate playa

3. Hydraulic conductivity studies and infiltration tests

4. Continuous coring of the vadose zone underway

• Chemostratigraphy (tracers - Cl, Nitrates; isotopes – 13C, 15N, 18O, 3H) • Lithostratigraphy (physical and chemical characterization) • Magnetostratigraphy (susceptibility, IRM) • Pedostratigraphy (modern and buried soils)


Regional Results



Vadose Zone Chemistry

22

Nitrate concentration (μg-N/g)

Tritium concentration (TU)

McMahon et al., 2006


Playas and High Plains Recharge; [email protected] Rainwater Basin Joint Venture 2017 23

GMD #3

GMD #4

GMD #5

GMD #1

GMD #2

Rangeland vadose zone; recharge = 5 mm/yr Irrigated farmland vadose zone; recharge = 40-50 mm/yr Irrigated farmland vadose zone; recharge = 100 mm/yr



Regional Study

• Environmental tracers – Stable isotopes: climate

– Tritium (3H), CFCs: recharge since 1950

– Radiocarbon (14C): recharge 500 – 35,000 years ago

• Agricultural contaminants – Recharge since 1950s

• Nitrate

• Pesticides

• Fertilizers

• New data and literature review

24

Tritium and CFCs in HPA groundwater

Red = detect

Blue = non-detect


Playa Recharge Pathways

25

From PLJV



Chemical Transit


Summary

• Playas provide: – Important recharge pathways to HPA

– Chemical transit rates increase

• Sedimentation issues

• Results vary playa to playa – (size, geology, climate, etc.)

• Work on-going to upscale results from individual playas to regional HPA


Thank You . . .

Funding and other support: EPA, KU, KGS, UW-Oshkosh, Conoco-Phillips, PLJV, US Fish & Wildlife, NRCS, KWO

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