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Scott J Ikard

I am a licensed Professional Engineer with thirteen years of professional research and project engineering experience in geophysics, hydrogeology, and hydrology, with auxiliary experiences in fluvial geomorphology, civil, and geotechnical engineering.

Currently, I am a Hydrologist in the Geophysics unit of the United States Geological Survey's Texas Water Science Center, in Austin, Texas. I plan and perform applied research studies and projects that broadly encompass proposals development, geophysical and hydrologic survey planning, instrumentation, data acquisition, data processing, and publication of surface, waterborne, airborne, and borehole hydrogeophysical data. The goals of my applied work frequently include delineation and correlation of aquifer systems, geophysical assessments of local and regional surface and ground water exchange-flow patterns, quantification and uncertainty analysis of hydraulic and geophysical properties of the vadose zone, confined and unconfined aquifers throughout the world.

 

United States Geological Survey. GS1315-11 Hydrologist/Geophysicist. Austin, Texas 06/2014 – Present

  • Oversight, site selection, planning and preparation, and coordination of groundwater conservation districts, river authorities, municipal and government agencies, and public stakeholders in research-drilling and near-surface hydrogeophysical projects.
  • Planning, implementation, and oversight of waterborne and land-based geophysical field surveys using time and frequency domain electromagnetics, self-potential mapping, electric resistance tomography, seismic refraction, dilution gaging, water-level monitoring, differential global positioning systems, Calibrated surface and borehole geophysical and hydrologic instruments, and performed troubleshooting of logging instruments and data acquisition systems in the field.
  • Performed field acquisition, pre-processing, inversion, and post-processing of vertical electrical soundings and transient electromagnetic soundings, as well as surface self-potential and electrical resistivity tomography data, to map alluvial and deep confined aquifers and produce conceptual hydro-stratigraphic models for groundwater flow modeling.
  • Developed data-processing codes and algorithms for (a) automated hydro-stratigraphic interpretation and geo-electric correlations from geophysical well logs and drillers logs, (b) automated baseflow separation and recession analysis, (c) digital signal processing, (d) groundwater flow modeling, particle tracking, parameter estimation and uncertainty analysis, (e) 2D and 3D forward and inverse modeling of self-potential and DC resistivity data using finite elements, finite differences, and linear filter theory.
  • Published innovative, novel research in peer-reviewed journals and USGS reports.

Science and Products

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Hamilton Creek

Investigation of Preferential Groundwater Seepage in the Ellenburger – San Saba Aquifer Using Geoelectric Measurements

The USGS Texas Water Science Center (TXWSC) is completing a geophysical pilot study adjacent to Hamilton Creek in Burnet County, central Texas. The pilot study is intended to test whether electrical geophysical methods can provide information regarding the locations of dissolution cavities and preferential groundwater flow within in the Ellenburger San-Saba aquifer. Data from this study will give...
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Oklahoma-Texas Water Science Center
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Investigation of Preferential Groundwater Seepage in the Ellenburger – San Saba Aquifer Using Geoelectric Measurements

The USGS Texas Water Science Center (TXWSC) is completing a geophysical pilot study adjacent to Hamilton Creek in Burnet County, central Texas. The pilot study is intended to test whether electrical geophysical methods can provide information regarding the locations of dissolution cavities and preferential groundwater flow within in the Ellenburger San-Saba aquifer. Data from this study will give...
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geophysical logging

Geoelectric and Seismic Characterization of the Precambrian Granite Gravel Aquifer, Llano Uplift, Central Texas

The USGS Texas Water Science Center (TXWSC) is testing the suitability of seismic refraction tomography (SRT) and time-domain electromagnetic sounding (TDEM) geophysical methods for mapping the contact boundary between the Granite Gravel aquifer and the underlying crystalline Town Mountain Granite bedrock in southwestern Burnet County. The Granite Gravel aquifer is anticipated to show a contrast...
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Oklahoma-Texas Water Science Center
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Geoelectric and Seismic Characterization of the Precambrian Granite Gravel Aquifer, Llano Uplift, Central Texas

The USGS Texas Water Science Center (TXWSC) is testing the suitability of seismic refraction tomography (SRT) and time-domain electromagnetic sounding (TDEM) geophysical methods for mapping the contact boundary between the Granite Gravel aquifer and the underlying crystalline Town Mountain Granite bedrock in southwestern Burnet County. The Granite Gravel aquifer is anticipated to show a contrast...
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Self-potential, electrical resistivity tomography, and water temperature and electrical conductivity data pertaining to the sources of groundwater at Krause Springs, Spicewood, Texas, February 4–15, 2019

This data release contains self-potential (SP), electrical resistivity tomography (ERT), and water temperature and conductivity data measured during a geophysical survey at the Krause Springs property in Spicewood, Texas. The geophysical survey was completed February 4–15, 2019, over approximately 3.1 acres on the western side of the property adjacent to the main visitor parking lot and entrance f
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Oklahoma-Texas Water Science Center

Waterborne Self-potential Data, Surface-water Temperature and Conductivity Logging data, and Electric Resistivity Tomography Data Measured at East Fork Poplar Creek, Oak Ridge, Tennessee, January-March 2022.

Geophysical data were collected on January 13, 2022, from a reach of East Fork Poplar Creek in Oak Ridge, Tennessee to gain a better understanding of surface water/groundwater exchanges. This data release contains the following types of data: waterborne self-potential (WaSP), and surface -water temperature and conductivity data collected by the U.S. Geological Survey (USGS) from 220-meter (m) long
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Oklahoma-Texas Water Science Center

Historical (1940–2006) and recent (2019–20) aquifer slug test datasets used to model transmissivity and hydraulic conductivity of the Mississippi River Valley alluvial aquifer from recent (2018–20) airborne electromagnetic (AEM) survey d

The Mississippi River Valley alluvial aquifer (“alluvial aquifer”) is one of the most extensively developed aquifers in the United States. The alluvial aquifer is present at the land surface in parts of southeastern Missouri, northeastern Louisiana, western Mississippi, western Tennessee and Kentucky near the Mississippi River, and throughout eastern Arkansas. Historical (1940–2006) and recent (20
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Oklahoma-Texas Water Science Center

Waterborne Gradient Self-potential, Temperature, and Conductivity Logging of the Upper part of the Delaware River between Hancock and Port Jervis, New York, June-July 2021

This data release contains waterborne gradient self-potential (SP), surface-water temperature, surface-water conductivity and specific conductance, and surface-water nitrate concentration data measured continuously in the upper part of the Delaware River along approximately 123 kilometers (km) between Hancock and Port Jervis, New York. All of the data were measured from a kayak between June 27 and
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Oklahoma-Texas Water Science Center, Pennsylvania Water Science Center

Waterborne Gradient Self-potential, Temperature, and Conductivity Logging of Lake Travis, Texas, near the Bee Creek Fault, March-April 2020

This data release provides gradient self-potential (SP), conductivity, and temperature measurements made during an investigation of surface-water and groundwater exchange in Lake Travis near Austin, Texas, where the Colorado River is incised into two zones of the Cretaceous-age Trinity aquifer (the lower-zone, and several hydrostratigraphic units of the middle zone). The voltage, temperature, and
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Oklahoma-Texas Water Science Center

Investigation of Scale-dependent Groundwater/Surface-water Exchange in Rivers by Gradient Self-Potential Logging: Numerical Model and Field Experiment Data, Quashnet River, Massachusetts, October 2017 (ver. 2.0, November 2020)

This data release contains waterborne self-potential (SP) logging data measured during 48 laboratory experiments and three field experiments that were performed to develop an efficient, accurate method for detecting (in the laboratory) and geolocating (in the field) focused vertical groundwater discharge (surface-water gains) and recharge (surface-water losses) in a river. The experimental procedu
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Oklahoma-Texas Water Science Center

650-m Profiles of Self-Potential, Contact Resistance, and Electric Resistance Tomography Measurements Adjacent to Hamilton Creek, Burnet County, Texas, July 2017 - January 2018

This data release consists of three different types of geoelectric data measured along three curvilinear profiles during two separate geophysical surveys completed on July 9, 2017 and January 9, 2018. The datasets include three self-potential (SP) profiles, two spatially-coincident electric contact-resistance (CR) profiles, and two spatially-coincident electric resistance tomography (ERT) tomogram
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Oklahoma-Texas Water Science Center

Data Used to Assess the Hydrogeologic Framework with Emphasis on the Ogallala and Edwards-Trinity Aquifers, in and Near Gaines, Terry, and Yoakum Counties, Texas, 2018

More than 11,500 well records, such as geophysical logs, drilling descriptions, and published hydrogeologic framework information, were evaluated to help characterize the framework of hydrogeologic units in and near Gaines, Terry, and Yoakum Counties, Texas. Additional geophysical data were collected to improve the spatial coverage across the study area and to reduce uncertainty with regard to hyd
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Oklahoma-Texas Water Science Center

14.86 km Profiles of the Electric and Self-potential Fields Measured in the Lower Guadalupe River Channel, Texas Interior Gulf Coastal Plain, September 2016

This data release consists of three geophysical data sets measured in the lower Guadalupe River channel, south-central Texas, and one supplementary geophysical data set measured in a laboratory. The lower Guadalupe River is incised into the outcrop of the Carrizo-Wilcox aquifer in south-central Texas. The river and the aquifer are hydraulically connected across the outcrop, although the connectivi
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Oklahoma-Texas Water Science Center
Filter Total Items: 14

A model of transmissivity and hydraulic conductivity from electrical resistivity distribution derived from airborne electromagnetic surveys of the Mississippi River Valley Alluvial Aquifer, Midwest USA

Groundwater-flow models require the spatial distribution of the hydraulic conductivity parameter. One approach to defining this spatial distribution in groundwater-flow model grids is to map the electrical resistivity distribution by airborne electromagnetic (AEM) survey and establish a petrophysical relation between mean resistivity calculated as a nonlinear function of the resistivity layering a
Authors
Scott Ikard, Burke J. Minsley, James Robert Rigby, Wade Kress
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Lower Mississippi-Gulf Water Science Center, Geology, Geophysics, and Geochemistry Science Center, Oklahoma-Texas Water Science Center

Geoelectric survey of the Granite Gravel aquifer, Llano Uplift, Central Texas, to determine locations for water wells

An electrical geophysical survey was completed within a small area of the Llano Uplift of central Texas to determine locations to install two water wells in the Granite Gravel aquifer (GGA). Electrical resistivity tomography (ERT) was performed along two 188-m long profiles that intersected at the approximate center of a 100-m by 100-m self-potential (SP) map. The ERT survey was completed to map t
Authors
Scott Ikard, David S. Wallace, Andrew Teeple, Gregory Stanton
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Waterborne gradient Self-Potential (WaSP) logging in the Rio Grande to map localized and regional surface and groundwater exchanges across the Mesilla Valley

The Rio Grande is the primary source of recharge to the Mesilla Basin/Conejos-Médanos aquifer system (“Mesilla Basin aquifer system”) in the Mesilla Valley of New Mexico and Texas. The Mesilla Basin aquifer system is the primary source of water supply to several large cities along the United States–Mexico border. Identifying gaining and losing reaches of the Rio Grande in the Mesilla Valley is the
Authors
Scott Ikard, Andrew Teeple
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Oklahoma-Texas Water Science Center

Investigation of scale-dependent groundwater/surface-water exchange in rivers by gradient self-potential logging: Numerical modeling and field experiments

Exchanges of groundwater and surface-water are fundamental to a wide range of water-supply and water-quality management issues but challenging to map beyond the reach scale. Waterborne gradient self-potential (SP) measurements are directly sensitive to water flow through riverbed sediments and can be used to infer exchange locations, direction (gain versus loss), scale, and relative changes, but t
Authors
Scott Ikard, Martin A. Briggs, John W. Lane
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Water Resources Mission Area

Effects of climate and land-use change on thermal springs recharge—A system-based coupled surface-water and groundwater-flow model for Hot Springs National Park, Arkansas

A three-dimensional hydrogeologic framework of the Hot Springs anticlinorium beneath Hot Springs National Park, Arkansas, was constructed to represent the complex hydrogeology of the park and surrounding areas to depths exceeding 9,000 feet below ground surface. The framework, composed of 6 rock formations and 1 vertical fault emplaced beneath the thermal springs, was discretized into 19 layers, 4
Authors
Rheannon M. Hart, Scott J. Ikard, Phillip D. Hays, Brian R. Clark
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Water Resources Mission Area, Science and Decisions Center, Lower Mississippi-Gulf Water Science Center

Gradient self-potential logging in the Rio Grande to identify gaining and losing reaches across the Mesilla Valley

The Rio Grande/Río Bravo del Norte (hereinafter referred to as the “Rio Grande”) is the primary source of recharge to the Mesilla Basin/Conejos-Médanos aquifer system in the Mesilla Valley of New Mexico and Texas. The Mesilla Basin aquifer system is the U.S. part of the Mesilla Basin/Conejos-Médanos aquifer system and is the primary source of water supply to several communities along the United St
Authors
Scott Ikard, Andrew Teeple, Delbert Humberson
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Geochemical assessment of the Hueco Bolson, New Mexico and Texas, 2016–17

Understanding groundwater quality in transboundary aquifers like the Hueco Bolson is important for the 2.7 million people along the United States and Mexico border living in and near the combined metropolitan areas of Ciudad Juárez, Mexico, and El Paso, Texas, who rely on groundwater for water supply. To better understand water-quality conditions in the Mexico–New Mexico–Texas transboundary area,
Authors
Patricia B. Ging, Delbert G. Humberson, Scott J. Ikard
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Preferential groundwater seepage in karst terrane inferred from geoelectric measurements

The Ellenburger–San Saba aquifer discharges spring flows into the overlying Hamilton Creek bed in Burnet County, central Texas. The aquifer is susceptible to contamination from surface‐water reservoirs because of the presence of dissolution cavities that are hydraulically connected to the reservoirs in some locations. There is concern that preferential groundwater seepage from reservoirs into the
Authors
Scott Ikard, Emily Pease
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

New insights into surface-water/groundwater exchanges in the Guadalupe River, Texas, from floating geophysical methods

In south-central Texas, the amount of streamflow in the Guadalupe River is a primary concern for local and downstream communities because of municipal, agricultural, wildlife, and recreational uses. Understanding the flow paths and rates of exchange between the surface water in the river and the groundwater in the underlying Carrizo-Wilcox aquifer is vital for understanding the water budget and st
Authors
Scott J. Ikard, J. Ryan Banta, Gregory P. Stanton
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

New insights on scale-dependent surface-groundwater exchange from a floating self-potential Dipole

In south-central Texas the lower Guadalupe River has incised into the outcrop of the Carrizo-Wilcox aquifer. The river and the aquifer are hydraulically connected across the outcrop, although the connectivity is obscured at the surface by alluvium and surface-water and groundwater exchange dynamics are currently poorly understood. To investigate surface-water and groundwater exchange dynamics betw
Authors
Scott Ikard, Andrew P. Teeple, Jason Payne, Gregory P. Stanton, J. Ryan Banta
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Water Resources Mission Area, Oklahoma-Texas Water Science Center

Hydrogeophysical investigations of earthen dams – Two California case studies

Excessive groundwater seepage can be a common engineering concern with earthen dams. The application of geophysical methods, whether for characterization or for long-term monitoring, to help inform mitigation strategies is becoming a more common addition to these investigations. The U.S. Geological Survey (USGS) has completed geophysical investigations at several earthen dams in cooperation with t
Authors
Bethany L. Burton, Paul A. Bedrosian, Burke J. Minsley, Scott Ikard, Michael H. Powers
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Geology, Geophysics, and Geochemistry Science Center

Improving our understanding of hydraulic-electrical relations: A case study of the surficial aquifer in Emirate Abu Dhabi

Transmissivity is a bulk hydraulic property that can be correlated with bulk electrical properties of an aquifer. In aquifers that are electrically-resistive relative to adjacent layers in a horizontally stratified sequence, transmissivity has been shown to correlate with bulk transverse resistance. Conversely, in aquifers that are electrically-conductive relative to adjacent layers, transmissivit
Authors
Scott Ikard, Wade H. Kress
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Water Resources Mission Area, Oklahoma-Texas Water Science Center, International Programs

Non-USGS Publications**

Ikard, S. J., A. Revil, A. Jardani, W. F. Woodruff, M. Parekh, and M. Mooney (2012), Saline pulse test monitoring with the self-potential method to nonintrusively determine the velocity of the pore water in leaking areas of earth dams and embankments, Water Resour. Res., 48, W04201, doi:10.1029/2010WR010247.
Ikard, S. J., Gooseff, M. N., Barrett, J. E. and Takacs‐Vesbach, C. (2009), Thermal characterisation of active layer across a soil moisture gradient in the McMurdo Dry Valleys, Antarctica. Permafrost Periglac. Process., 20: 27-39. doi:10.1002/ppp.634

**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