The Distribution of Permeable Zones Within the Ogallala in the Southwest Kansas Groundwater

Management District 3

PRESENTED BY

P. ALLEN MACFARLANE and NICHOLAS SCHNEIDERGEOHYDROLOGY SECTION

KANSAS GEOLOGICAL SURVEY

Saturated Thickness: The Key to Assessment of Regional Aquifer Conditions

Practical Saturated Thickness (PST): A Better Measure of Ground-Water Availability

Definition: The saturated portion of a heterogeneous aquifer that yields water to pumping wells at significant rates.

Silt/clay

Water Table

Land SurfaceWell

Bedrock

SaturatedThickness

Practical SaturatedThickness

Research Objectives

• Update the bedrock surface elevation map using the data generated from drilling since about 1980.

• Use drillers’ logs of test holes and holes drilled for production wells to analyze in 2-D and 3-D the distribution of permeable, water-yielding zones.

Setting

Arkansas R.

Cimarron R.

StudyArea

“…a heterogeneous complex of clastic deposits.”

“Throughout this heterogeneous assortment of sediments there is virtually no distinctive bed that can be traced appreciable distances in the field.”

Frye et al. (1956)

Lithologies & Their Distribution

Data Point Type & Distribution

Methodology for Determining Permeable Fraction Distribution

• Interpretation of the drillers’ logs.

• Evaluation and selection of the drillers’ logs.

• Database development using Excel for input into RockWorks® 2004.

• Production of 2-D and 3-D images using ARC-GIS & RockWorks® 2004.

• Georeferencing and well-site surface elevation.

Methodology Issues

• Non uniformity in the drillers’ use of terminology.

• Amount of detail in the log.

• Reported well-log location accuracy.

• Lack of subsurface stratigraphic control.

Permeable Fraction Calculation

Aggregate Water-yielding Fraction Distribution

52%

N = 7,317

Permeable Sediment Percentage of Total Thickness

Subregional & Local Study Areas

Strip SubregionCentral GMD3Subregion

NE HaskellArea

Northeast Haskell Index Well & Local Area

2,220 ft 2,260

2,300

2,340

2,380

2,420

2,460

2,500

2,540

2,580

2,620

NE Haskell Co.Well

BedrockElevation

NE Haskell Local Area

NE Haskell Co.

Well

0

400 ft

NW SEPermeable

Fraction

NE Haskell Local Area

0

400 ft

NE Haskell Co.Well

NE SW

PermeableFraction

The Central GMD 3 Subregion

Water-yielding Fraction

a. b. c.

d. e.

N

The Strip Subregion

Water-yielding Fraction

Closest point, smoothed Closest point, unsmoothedwith high fidelity

The Strip Subregion - Model Comparisons

2006 Saturated Water-Yielding Zone Fraction

What Do These Visualizations Tell Us About the Distribution & Continuity of Permeable Units in

the Cenozoic Deposits in GMD 3?

• Laterally and vertically continuous high permeability pathways and confining layers can be discerned at local to subregional scales using the interval data from the drillers’ logs.

• In general, the valleys incised into bedrock are as likely to be filled with higher-percentage, water-yielding sediment as they are to be filled with moderate to lower percentage, water-yielding sediment.

• On the whole only about half of the Cenozoic sequence consists sediment capable of yielding or transmitting significant amounts of water to high-capacity wells in GMD 3.

• At subregional and regional scales, the sequence generally contains a higher percentage of water-yielding sediment in central part of the GMD than in the eastern part.