Katherine J Knierim, Ph.D. PG
Katherine (Kathy) Knierim is a hydrologist with the Lower Mississippi-Gulf Water Science Center in Little Rock, Arkansas. Her research focuses on groundwater quality.
I have worked on a diversity of projects throughout my career with the USGS and maintain a focus on groundwater. I contributed to the Ozark Plateaus Groundwater Availability project, which developed a groundwater flow model of the Ozark Plateaus Regional Aquifer System (https://www.usgs.gov/publications/ozark-plateaus-regional-aquifer-study-documentation-a-groundwater-flow-model). I was a team member and lead modeler for a National Water Quality Assessment Project which used machine learning to predict groundwater quality in the Mississippi Embayment Regional Aquifer System (https://www.sciencebase.gov/catalog/item/5e8de0e282cee42d13468793). I also led the Mississippi Alluvial Plain Project Water Quality task, which collected groundwater age tracers to characterize the age and recharge rates of one of the Nation's most heavily pumped groundwater aquifers.
I'm currently a team member for a national groundwater quality project, where we are using machine learning to predict salinity. I'm also working collaboratively with the Geology, Energy & Minerals Science Center to characterize lithium in the Smackover Formation (https://www.usgs.gov/centers/geology-energy-and-minerals-science-center/science/oil-and-gas-waters-project). Additionally, I work with local and State partners to help leverage USGS expertise to answer questions about water quality and availability.
Professional Experience
Hydrologist, U.S. Geological Survey, Little Rock, AR 2015 - current
Education and Certifications
Doctor of Philosophy in Environmental Dynamics, University of Arkansas, Fayetteville, AR, 2015
Master of Science in Geology, University of Arkansas, Fayetteville, AR, 2009
Bachelor of Science with University Honors in Geology, Bowling Green State University, Bowling Green, OH, 2007
Affiliations and Memberships*
Geological Society of America, Hydrogeology Division
Science and Products
Lithium observations, machine-learning predictions, and mass estimates from the Smackover Formation brines in southern Arkansas
Global demand for lithium, the primary component of lithium-ion batteries, greatly exceeds known supplies and this imbalance is expected to increase as the world transitions away from fossil fuel energy sources. The goal of this work was to calculate the total lithium mass in brines of the Reynolds oolite unit of the Smackover Formation in southern Arkansas using predicted lithium concentrations f
U.S. Geological Survey National Produced Waters Geochemical Database (ver. 3.0, December 2023)
During hydrocarbon production, water is typically co-produced from the geologic formations producing oil and gas. Understanding the composition of these produced waters is important to help investigate the regional hydrogeology, the source of the water, the efficacy of water treatment and disposal plans, potential economic benefits of mineral commodities in the fluids, and the safety of potential
Machine-learning model predictions and rasters of groundwater salinity in the Mississippi Alluvial Plain
Groundwater from the Mississippi River Valley alluvial aquifer (MRVA), coincident with the Mississippi Alluvial Plain (MAP), is a vital resource for agriculture and drinking-water supplies in the central United States. Water availability can be limited in some areas of the aquifer by high concentrations of salinity, measured as specific conductance. Boosted regression trees (BRT), a type of ensemb
Datasets for the 2015 potentiometric surface and water-level changes (2011-2013, 2013-2015) in the Sparta-Memphis aquifer, in Arkansas
These datasets provide the locations of and groundwater-level altitudes from 273 wells that were used to construct a 2015 potentiometric contour surface of the Sparta-Memphis aquifer. Measurements were made from January through June 2015 and represent synoptic conditions. All wells were cased completely in and screened in the Sparta-Memphis aquifer. Groundwater-level data are also available from t
Machine-learning model predictions and rasters of arsenic and manganese in groundwater in the Mississippi River Valley alluvial aquifer
Groundwater from the Mississippi River Valley alluvial aquifer (MRVA) is a vital resource for agriculture and drinking-water supplies in the central United States. Water availability can be limited in some areas of the aquifer by high concentrations of trace elements, including manganese and arsenic. Boosted regression trees, a type of ensemble-tree machine-learning method, were used to predict ma
Machine-learning model predictions and rasters of dissolved oxygen probability, iron concentration, and redox conditions in groundwater in the Mississippi River Valley alluvial and Claiborne aquifers
Groundwater is a vital resource in the Mississippi embayment physiographic region (Mississippi embayment) of the central United States and can be limited in some areas by high concentrations of trace elements. The concentration of trace elements in groundwater is largely driven by oxidation-reduction (redox) processes. Redox processes are a group of biotically driven reactions in which energy is d
Simulated groundwater residence times in two principal aquifers of the Mississippi embayment physiographic region
Groundwater residence times and flow path lengths were simulated for two major aquifers of the Mississippi embayment region using particle tracking (Pollock, 2012; Starn and Belitz, 2018) in a regional groundwater-flow model (Haugh and others, 2020). The Mississippi embayment physiographic region includes two principal aquifer systems: the surficial aquifer system, which is dominated by the Quater
Prediction grids of pH for the Mississippi River Valley Alluvial and Claiborne Aquifers
Groundwater is a vital resource to the Mississippi embayment region of the central United States. Regional and integrated assessments of water availability that link physical flow models and water quality in principal aquifer systems provide context for the long-term availability of these water resources. An innovative approach using machine learning was employed to predict groundwater pH across d
Machine-learning model predictions and groundwater-quality rasters of specific conductance, total dissolved solids, and chloride in aquifers of the Mississippi embayment
Groundwater is a vital resource in the Mississippi embayment of the central United States. An innovative approach using machine learning (ML) was employed to predict groundwater salinity - including specific conductance (SC), total dissolved solids (TDS), and chloride (Cl) concentrations - across three drinking-water aquifers of the Mississippi embayment. A ML approach was used because it accommod
Carbonate geochemistry dataset of the soil and an underlying cave in the Ozark Plateaus, central United States
The nature of carbon (C) cycling in the vadose zone where groundwater is in contact with abundant gas-filled voids is poorly understood. The objective of this study was to trace C cycling in a karst landscape using stable-C isotopes, with emphasis on a shallow groundwater flow path through the soil, to an underlying cave, and to the spring outlet of a cave stream in the Ozark Plateaus of northwest
Groundwater withdrawal rates from the Ozark Plateaus aquifer system, 1900 to 2010
Groundwater is an often overlooked freshwater resource compared to surface water, but groundwater is used widely across the United States, especially during periods of drought. If groundwater models can successfully simulate past conditions, they may be used to evaluate potential future pumping scenarios or climate conditions, thus providing a valuable planning tool for water-resource managers. Qu
Machine-learning predictions of redox conditions in groundwater in the Mississippi River Valley alluvial and Claiborne aquifers, south-central United States
Machine-learning models developed by the U.S. Geological Survey were used to predict iron concentrations and the probability of dissolved oxygen (DO) concentrations exceeding a threshold of 1 milligram per liter (mg/L) in groundwater in aquifers of the Mississippi embayment physiographic region. DO and iron concentrations are driven by and reflect the oxidation-reduction (redox) conditions in grou
Predicted pH of groundwater in the Mississippi River Valley alluvial and Claiborne aquifers, south-central United States
Regional aquifers in the Mississippi embayment are the principal sources of water used for public and domestic supply, irrigation, and industrial uses throughout the region. An understanding of how water quality varies spatially, temporally, and with depth are critical aspects to ensuring long-term sustainable use of these resources. A boosted regression tree (BRT) model was used by the U.S. Geolo
Filter Total Items: 15
Machine-learning predictions of groundwater specific conductance in the Mississippi Alluvial Plain, south-central United States, with evaluation of regional geophysical aerial electromagnetic data as explanatory variables
The Mississippi Alluvial Plain, located in the south-central United States, is undergoing long-term groundwater-level declines within the surficial Mississippi River Valley alluvial aquifer (hereinafter referred to as “alluvial aquifer”), which has raised concerns about future groundwater availability. In some parts of the alluvial aquifer, groundwater availability for common uses such as irrigati
Authors
Courtney D. Killian, Katherine J. Knierim
Potentiometric surfaces (2013, 2015), groundwater quality (2010–15), and water-level changes (2011–13, 2013–15) in the Sparta-Memphis aquifer in Arkansas
The Sparta-Memphis aquifer, present across much of eastern Arkansas, is the second most used groundwater resource in the State, with the Mississippi River Valley alluvial aquifer being the primary groundwater resource. The U.S. Geological Survey, in cooperation with Arkansas Department of Agriculture-Natural Resources Division, Arkansas Geological Survey, Natural Resources Conservation Service, Un
Authors
Anna M. Nottmeier, Katherine J. Knierim, Phillip D. Hays
Salinity and total dissolved solids measurements for natural waters: An overview and a new salinity method based on specific conductance and water type
The total concentration of dissolved constituents in water is routinely quantified by measurements of salinity or total dissolved solids (TDS). However, salinity and TDS are operationally defined by their analytical methods and are not equivalent for most waters. Furthermore, multiple methods are available to determine salinity and TDS, and these methods have inherent differences. TDS is defined a
Authors
R. Blaine McCleskey, Charles A. Cravotta, Matthew P. Miller, Fred D. Tillman, Paul Stackelberg, Katherine J. Knierim, Daniel Wise
Mapped predictions of manganese and arsenic in an alluvial aquifer using boosted regression trees
Manganese (Mn) concentrations and the probability of arsenic (As) exceeding the drinking-water standard of 10 μg/L were predicted in the Mississippi River Valley alluvial aquifer (MRVA) using boosted regression trees (BRT). BRT, a type of ensemble-tree machine-learning model, were created using predictor variables that affect Mn and As distribution in groundwater. These variables included iron (Fe
Authors
Katherine J. Knierim, James A. Kingsbury, Kenneth Belitz, Paul Stackelberg, Burke J. Minsley, James R. Rigby
Airborne geophysical surveys of the lower Mississippi Valley demonstrate system-scale mapping of subsurface architecture
The Mississippi Alluvial Plain hosts one of the most prolific shallow aquifer systems in the United States but is experiencing chronic groundwater decline. The Reelfoot rift and New Madrid seismic zone underlie the region and represent an important and poorly understood seismic hazard. Despite its societal and economic importance, the shallow subsurface architecture has not been mapped with the sp
Authors
Burke J. Minsley, James R. Rigby, Stephanie R. James, Bethany L. Burton, Katherine J. Knierim, Michael Pace, Paul A. Bedrosian, Wade Kress
The impact of ventilation patterns on calcite dissolution rates within karst conduits
Erosion rates in streams vary dramatically over time, as differences in streamflow and sediment load enhance or inhibit erosion processes. Within cave streams, and other bedrock channels incising soluble rocks, changes in water chemistry are an important factor in determining how erosion rates will vary in both time and space. Prior studies in surface streams, springs, and caves suggest that varia
Authors
Matthew D. Covington, Katherine J. Knierim, Holly H Young, Josue Rodriguez, Hannah Gnoza
Using boosted regression tree models to predict salinity in Mississippi embayment aquifers, central United States
High salinity limits groundwater use in parts of the Mississippi embayment. Machine learning was used to create spatially continuous and three‐dimensional predictions of salinity across drinking‐water aquifers in the embayment. Boosted regression tree (BRT) models, a type of machine learning, were used to predict specific conductance (SC) and chloride (Cl), and total dissolved solids (TDS) was cal
Authors
Katherine J. Knierim, James A. Kingsbury, Connor J. Haugh, Katherine Marie Ransom
Groundwater availability in the Ozark Plateaus aquifer system
Executive SummaryThe study described in this report, initiated by the U.S. Geological Survey in 2014, was designed to evaluate fresh groundwater resources within the Ozark Plateaus, central United States, as an area within a broader national assessment of groundwater availability. The goals of the Ozark study were to evaluate historical effects of human activities on water levels and groundwater a
Authors
Brian R. Clark, Leslie L. Duncan, Katherine J. Knierim
Encylopedia of Caves
For many people, a visit to a cave is a wondrous event directing our minds to ponder the mysteries presented by these unique places
and inspiring questions: How old is the cave? What was the role of water in forming the cave and where did the water come from?
How is the cave connected to the surface environment? These are intriguing questions to ask, and karst scientists use isotope
geochemistry t
Authors
Katherine J. Knierim, Phillip D. Hays
The Ozark Plateaus Regional Aquifer Study—Documentation of a groundwater-flow model constructed to assess water availability in the Ozark Plateaus
Recent short-term drought conditions have emphasized the need to better understand the delicate balance between abundance, sustainability, and scarcity of groundwater in the Ozark Plateaus aquifer system. In 2014, the U.S. Geological Survey began construction of a groundwater-flow model as a tool for the assessment of groundwater availability in the Ozark Plateaus aquifer system. The model was dev
Authors
Brian R. Clark, Joseph M. Richards, Katherine J. Knierim
Challenges for creating a site-specific groundwater-use record for the Ozark Plateaus aquifer system (central USA) from 1900 to 2010
Hydrologic budgets to determine groundwater availability are important tools for water-resource managers. One challenging component for developing hydrologic budgets is quantifying water use through time because historical and site-specific water-use data can be sparse or poorly documented. This research developed a groundwater-use record for the Ozark Plateaus aquifer system (central USA) from 19
Authors
Katherine J. Knierim, Anna M. Nottmeier, Scott C. Worland, Drew A. Westerman, Brian R. Clark
Carbon cycling in the mantled karst of the Ozark Plateaus, central United States
The nature of carbon (C) cycling in the unsaturated zone where groundwater is in contact with abundant gas-filled voids is poorly understood. The objective of this study was to trace inorganic-C cycling in a karst landscape using stable-C isotopes, with emphasis on a shallow groundwater flow path through the soil, to an underlying cave, and to the spring outlet of a cave stream in the Ozark Platea
Authors
Katherine J. Knierim, Erik D. Pollock, Matthew D. Covington, Phillip D. Hays, Kristofor R. Brye
Non-USGS Publications**
Knierim, K.J., Hays, P.D., and Bowman, D., 2015, Quantifying the variability in Escherichia coli (E. coli) throughout storm events at a karst spring in northwestern Arkansas, United States: Environmental Earth Sciences, v. 74, p. 4607–4623, doi: 10.1007/s12665-015-4416-5.
Knierim, K., Turner, H., and Davis, R.K., 2015, Two-Stage Exams Improve Student Learning in an Introductory Geology Course: Logistics, Attendance, and Grades: Journal of Geoscience Education, v. 63, p. 157–164, doi: 10.5408/14-051.1
Knierim, K.J. and Hays, P.D., 2014, PECCI Code (PythonTM Estimation for Carbon Concentration and Isotopes) for calculating the concentration and stable carbon isotopic composition of dissolved inorganic carbon (DIC) in precipitation for northwestern Arkansas: Arkansas Water Resources Center MSC Publication 370, 26 p.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Lithium observations, machine-learning predictions, and mass estimates from the Smackover Formation brines in southern Arkansas
Global demand for lithium, the primary component of lithium-ion batteries, greatly exceeds known supplies and this imbalance is expected to increase as the world transitions away from fossil fuel energy sources. The goal of this work was to calculate the total lithium mass in brines of the Reynolds oolite unit of the Smackover Formation in southern Arkansas using predicted lithium concentrations f
U.S. Geological Survey National Produced Waters Geochemical Database (ver. 3.0, December 2023)
During hydrocarbon production, water is typically co-produced from the geologic formations producing oil and gas. Understanding the composition of these produced waters is important to help investigate the regional hydrogeology, the source of the water, the efficacy of water treatment and disposal plans, potential economic benefits of mineral commodities in the fluids, and the safety of potential
Machine-learning model predictions and rasters of groundwater salinity in the Mississippi Alluvial Plain
Groundwater from the Mississippi River Valley alluvial aquifer (MRVA), coincident with the Mississippi Alluvial Plain (MAP), is a vital resource for agriculture and drinking-water supplies in the central United States. Water availability can be limited in some areas of the aquifer by high concentrations of salinity, measured as specific conductance. Boosted regression trees (BRT), a type of ensemb
Datasets for the 2015 potentiometric surface and water-level changes (2011-2013, 2013-2015) in the Sparta-Memphis aquifer, in Arkansas
These datasets provide the locations of and groundwater-level altitudes from 273 wells that were used to construct a 2015 potentiometric contour surface of the Sparta-Memphis aquifer. Measurements were made from January through June 2015 and represent synoptic conditions. All wells were cased completely in and screened in the Sparta-Memphis aquifer. Groundwater-level data are also available from t
Machine-learning model predictions and rasters of arsenic and manganese in groundwater in the Mississippi River Valley alluvial aquifer
Groundwater from the Mississippi River Valley alluvial aquifer (MRVA) is a vital resource for agriculture and drinking-water supplies in the central United States. Water availability can be limited in some areas of the aquifer by high concentrations of trace elements, including manganese and arsenic. Boosted regression trees, a type of ensemble-tree machine-learning method, were used to predict ma
Machine-learning model predictions and rasters of dissolved oxygen probability, iron concentration, and redox conditions in groundwater in the Mississippi River Valley alluvial and Claiborne aquifers
Groundwater is a vital resource in the Mississippi embayment physiographic region (Mississippi embayment) of the central United States and can be limited in some areas by high concentrations of trace elements. The concentration of trace elements in groundwater is largely driven by oxidation-reduction (redox) processes. Redox processes are a group of biotically driven reactions in which energy is d
Simulated groundwater residence times in two principal aquifers of the Mississippi embayment physiographic region
Groundwater residence times and flow path lengths were simulated for two major aquifers of the Mississippi embayment region using particle tracking (Pollock, 2012; Starn and Belitz, 2018) in a regional groundwater-flow model (Haugh and others, 2020). The Mississippi embayment physiographic region includes two principal aquifer systems: the surficial aquifer system, which is dominated by the Quater
Prediction grids of pH for the Mississippi River Valley Alluvial and Claiborne Aquifers
Groundwater is a vital resource to the Mississippi embayment region of the central United States. Regional and integrated assessments of water availability that link physical flow models and water quality in principal aquifer systems provide context for the long-term availability of these water resources. An innovative approach using machine learning was employed to predict groundwater pH across d
Machine-learning model predictions and groundwater-quality rasters of specific conductance, total dissolved solids, and chloride in aquifers of the Mississippi embayment
Groundwater is a vital resource in the Mississippi embayment of the central United States. An innovative approach using machine learning (ML) was employed to predict groundwater salinity - including specific conductance (SC), total dissolved solids (TDS), and chloride (Cl) concentrations - across three drinking-water aquifers of the Mississippi embayment. A ML approach was used because it accommod
Carbonate geochemistry dataset of the soil and an underlying cave in the Ozark Plateaus, central United States
The nature of carbon (C) cycling in the vadose zone where groundwater is in contact with abundant gas-filled voids is poorly understood. The objective of this study was to trace C cycling in a karst landscape using stable-C isotopes, with emphasis on a shallow groundwater flow path through the soil, to an underlying cave, and to the spring outlet of a cave stream in the Ozark Plateaus of northwest
Groundwater withdrawal rates from the Ozark Plateaus aquifer system, 1900 to 2010
Groundwater is an often overlooked freshwater resource compared to surface water, but groundwater is used widely across the United States, especially during periods of drought. If groundwater models can successfully simulate past conditions, they may be used to evaluate potential future pumping scenarios or climate conditions, thus providing a valuable planning tool for water-resource managers. Qu
Machine-learning predictions of redox conditions in groundwater in the Mississippi River Valley alluvial and Claiborne aquifers, south-central United States
Machine-learning models developed by the U.S. Geological Survey were used to predict iron concentrations and the probability of dissolved oxygen (DO) concentrations exceeding a threshold of 1 milligram per liter (mg/L) in groundwater in aquifers of the Mississippi embayment physiographic region. DO and iron concentrations are driven by and reflect the oxidation-reduction (redox) conditions in grou
Predicted pH of groundwater in the Mississippi River Valley alluvial and Claiborne aquifers, south-central United States
Regional aquifers in the Mississippi embayment are the principal sources of water used for public and domestic supply, irrigation, and industrial uses throughout the region. An understanding of how water quality varies spatially, temporally, and with depth are critical aspects to ensuring long-term sustainable use of these resources. A boosted regression tree (BRT) model was used by the U.S. Geolo
Filter Total Items: 15
Machine-learning predictions of groundwater specific conductance in the Mississippi Alluvial Plain, south-central United States, with evaluation of regional geophysical aerial electromagnetic data as explanatory variables
The Mississippi Alluvial Plain, located in the south-central United States, is undergoing long-term groundwater-level declines within the surficial Mississippi River Valley alluvial aquifer (hereinafter referred to as “alluvial aquifer”), which has raised concerns about future groundwater availability. In some parts of the alluvial aquifer, groundwater availability for common uses such as irrigati
Authors
Courtney D. Killian, Katherine J. Knierim
Potentiometric surfaces (2013, 2015), groundwater quality (2010–15), and water-level changes (2011–13, 2013–15) in the Sparta-Memphis aquifer in Arkansas
The Sparta-Memphis aquifer, present across much of eastern Arkansas, is the second most used groundwater resource in the State, with the Mississippi River Valley alluvial aquifer being the primary groundwater resource. The U.S. Geological Survey, in cooperation with Arkansas Department of Agriculture-Natural Resources Division, Arkansas Geological Survey, Natural Resources Conservation Service, Un
Authors
Anna M. Nottmeier, Katherine J. Knierim, Phillip D. Hays
Salinity and total dissolved solids measurements for natural waters: An overview and a new salinity method based on specific conductance and water type
The total concentration of dissolved constituents in water is routinely quantified by measurements of salinity or total dissolved solids (TDS). However, salinity and TDS are operationally defined by their analytical methods and are not equivalent for most waters. Furthermore, multiple methods are available to determine salinity and TDS, and these methods have inherent differences. TDS is defined a
Authors
R. Blaine McCleskey, Charles A. Cravotta, Matthew P. Miller, Fred D. Tillman, Paul Stackelberg, Katherine J. Knierim, Daniel Wise
Mapped predictions of manganese and arsenic in an alluvial aquifer using boosted regression trees
Manganese (Mn) concentrations and the probability of arsenic (As) exceeding the drinking-water standard of 10 μg/L were predicted in the Mississippi River Valley alluvial aquifer (MRVA) using boosted regression trees (BRT). BRT, a type of ensemble-tree machine-learning model, were created using predictor variables that affect Mn and As distribution in groundwater. These variables included iron (Fe
Authors
Katherine J. Knierim, James A. Kingsbury, Kenneth Belitz, Paul Stackelberg, Burke J. Minsley, James R. Rigby
Airborne geophysical surveys of the lower Mississippi Valley demonstrate system-scale mapping of subsurface architecture
The Mississippi Alluvial Plain hosts one of the most prolific shallow aquifer systems in the United States but is experiencing chronic groundwater decline. The Reelfoot rift and New Madrid seismic zone underlie the region and represent an important and poorly understood seismic hazard. Despite its societal and economic importance, the shallow subsurface architecture has not been mapped with the sp
Authors
Burke J. Minsley, James R. Rigby, Stephanie R. James, Bethany L. Burton, Katherine J. Knierim, Michael Pace, Paul A. Bedrosian, Wade Kress
The impact of ventilation patterns on calcite dissolution rates within karst conduits
Erosion rates in streams vary dramatically over time, as differences in streamflow and sediment load enhance or inhibit erosion processes. Within cave streams, and other bedrock channels incising soluble rocks, changes in water chemistry are an important factor in determining how erosion rates will vary in both time and space. Prior studies in surface streams, springs, and caves suggest that varia
Authors
Matthew D. Covington, Katherine J. Knierim, Holly H Young, Josue Rodriguez, Hannah Gnoza
Using boosted regression tree models to predict salinity in Mississippi embayment aquifers, central United States
High salinity limits groundwater use in parts of the Mississippi embayment. Machine learning was used to create spatially continuous and three‐dimensional predictions of salinity across drinking‐water aquifers in the embayment. Boosted regression tree (BRT) models, a type of machine learning, were used to predict specific conductance (SC) and chloride (Cl), and total dissolved solids (TDS) was cal
Authors
Katherine J. Knierim, James A. Kingsbury, Connor J. Haugh, Katherine Marie Ransom
Groundwater availability in the Ozark Plateaus aquifer system
Executive SummaryThe study described in this report, initiated by the U.S. Geological Survey in 2014, was designed to evaluate fresh groundwater resources within the Ozark Plateaus, central United States, as an area within a broader national assessment of groundwater availability. The goals of the Ozark study were to evaluate historical effects of human activities on water levels and groundwater a
Authors
Brian R. Clark, Leslie L. Duncan, Katherine J. Knierim
Encylopedia of Caves
For many people, a visit to a cave is a wondrous event directing our minds to ponder the mysteries presented by these unique places
and inspiring questions: How old is the cave? What was the role of water in forming the cave and where did the water come from?
How is the cave connected to the surface environment? These are intriguing questions to ask, and karst scientists use isotope
geochemistry t
Authors
Katherine J. Knierim, Phillip D. Hays
The Ozark Plateaus Regional Aquifer Study—Documentation of a groundwater-flow model constructed to assess water availability in the Ozark Plateaus
Recent short-term drought conditions have emphasized the need to better understand the delicate balance between abundance, sustainability, and scarcity of groundwater in the Ozark Plateaus aquifer system. In 2014, the U.S. Geological Survey began construction of a groundwater-flow model as a tool for the assessment of groundwater availability in the Ozark Plateaus aquifer system. The model was dev
Authors
Brian R. Clark, Joseph M. Richards, Katherine J. Knierim
Challenges for creating a site-specific groundwater-use record for the Ozark Plateaus aquifer system (central USA) from 1900 to 2010
Hydrologic budgets to determine groundwater availability are important tools for water-resource managers. One challenging component for developing hydrologic budgets is quantifying water use through time because historical and site-specific water-use data can be sparse or poorly documented. This research developed a groundwater-use record for the Ozark Plateaus aquifer system (central USA) from 19
Authors
Katherine J. Knierim, Anna M. Nottmeier, Scott C. Worland, Drew A. Westerman, Brian R. Clark
Carbon cycling in the mantled karst of the Ozark Plateaus, central United States
The nature of carbon (C) cycling in the unsaturated zone where groundwater is in contact with abundant gas-filled voids is poorly understood. The objective of this study was to trace inorganic-C cycling in a karst landscape using stable-C isotopes, with emphasis on a shallow groundwater flow path through the soil, to an underlying cave, and to the spring outlet of a cave stream in the Ozark Platea
Authors
Katherine J. Knierim, Erik D. Pollock, Matthew D. Covington, Phillip D. Hays, Kristofor R. Brye
Non-USGS Publications**
Knierim, K.J., Hays, P.D., and Bowman, D., 2015, Quantifying the variability in Escherichia coli (E. coli) throughout storm events at a karst spring in northwestern Arkansas, United States: Environmental Earth Sciences, v. 74, p. 4607–4623, doi: 10.1007/s12665-015-4416-5.
Knierim, K., Turner, H., and Davis, R.K., 2015, Two-Stage Exams Improve Student Learning in an Introductory Geology Course: Logistics, Attendance, and Grades: Journal of Geoscience Education, v. 63, p. 157–164, doi: 10.5408/14-051.1
Knierim, K.J. and Hays, P.D., 2014, PECCI Code (PythonTM Estimation for Carbon Concentration and Isotopes) for calculating the concentration and stable carbon isotopic composition of dissolved inorganic carbon (DIC) in precipitation for northwestern Arkansas: Arkansas Water Resources Center MSC Publication 370, 26 p.
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government