Lab Fellow, Chief Geophysicist
Lab Fellow, Chief Geophysicist


Fred Day-Lewis joined Pacific Northwest National Laboratory (PNNL) in 2021 as a chief geophysicist. Day-Lewis specializes in applied research projects related to subsurface characterization and monitoring, groundwater remediation, groundwater/surface-water exchange, geophysical inverse problems, thermal methods, hydrologic parameter estimation, and petrophysics.

Day-Lewis currently serves as an associate editor for the journal Groundwater and previously served as an associate editor for Water Resources Research, Geosphere, and Hydrogeology journals. He co-edited the American Geophysical Union monograph, Subsurface Hydrology: Data Integration for Properties and Processes. Day-Lewis is a past president of the American Geophysical Union Near Surface Geophysics Section, and past vice president of the Environmental and Engineering Geophysics Society. He was elected Fellow of the Geological Society of America in 2015 for seminal contributions to hydrogeophysics. Prior to coming to PNNL, Day-Lewis worked for the U.S. Geological Survey for 18 years as a research hydrologist.

Research Interest

  • Hydrogeophysics
  • Groundwater/surface-water exchange
  • Real-time geophysical monitoring
  • Predictive data analytics, inverse modeling, and parameter estimation
  • Digital signal processing

Disciplines and Skills

  • Aquifer Testing
  • Control Engineering
  • Digital Signal Processing
  • Environmental Characterization
  • Environmental Data Analysis
  • Environmental Management
  • Environmental Remediation
  • Fiber Optic Sensors
  • Geophysical Monitoring
  • Geophysical Surveys
  • Geophysics
  • Geostatistics
  • Groundwater
  • Groundwater Contamination
  • Groundwater Modeling
  • Hydrogeology
  • Inverse Problems
  • Parameter Estimation
  • Petrophysics
  • Python
  • Real-Time Analysis
  • Time Series Analysis
  • Tomography
  • Watershed Modeling
  • Wavelets


  • PhD in Hydrogeology, Stanford University
  • BS in Hydrology, University of New Hampshire
  • BA in English, University of New Hampshire

Affiliations and Professional Service

  • American Geophysical Union
  • Geological Society of America
  • Society of Exploration Geophysicists
  • National Groundwater Association

Awards and Recognitions

  • Fellow, Geological Society of America



  • Mangel A.R., D.C. Linneman, D. Sirota, J.M. Knox, D.P. Sprinkle, F.D. Day-Lewis, and C.E. Strickland, et al. 2023. Deep Vadose Zone Monitoring Test Bed: FY23 Status Report. PNNL-34956. Richland, WA: Pacific Northwest National Laboratory. Deep Vadose Zone Monitoring Test Bed: FY23 Status Report
  • Robinson J.L., J.T. St. Clair, J.N. Thomle, P. Jaysaval, J. Cambeiro, K.A. Peta, and F.D. Day-Lewis, et al. 2023. "Using multiple geophysical methods to refine a stratigraphic conceptual site model at a nuclear waste site." Environmental Processes 10. PNNL-SA-177749. doi:10.1007/s40710-023-00622-1
  • Thompson J.H., A.R. Mangel, and F.D. Day-Lewis. 2023. "A Geophysical Remediation Monitoring Method Selection Tool (GRM-MST)." Groundwater 61, no. 1:8-10. PNNL-SA-177934. doi:10.1111/gwat.13268


  • Day-Lewis F.D., and T.C. Johnson. 2022. Pore-Scale Simulation of Spectral Induced Polarization. PNNL-33729. Richland, WA: Pacific Northwest National Laboratory. Pore-Scale Simulation of Spectral Induced Polarization
  • Day-Lewis F.D., P.D. Royer, L.A. Placzek, and K.E. Markham. 2022. "A Multi-Scale Temperature-Based Strategy to Map Hydrologic Exchange Flows in Highly Dynamic Systems." Frontiers in Water 10. PNNL-SA-178043. doi:10.3389/feart.2022.1070393
  • McAliley W.A., F.D. Day-Lewis, D.A. Rey, M. Briggs, A.M. Shapiro, and D. Werkema. 2022. "Application of Recursive Estimation to Heat Tracing for Groundwater/Surface-Water Exchange." Water Resources Research 58, no. 6:e2021WR030443. PNNL-SA-165706. doi:10.1029/2021WR030443
  • Robinson J.L., J.N. Thomle, D.P. McFarland, K.A. Deters, M.L. Rockhold, F.D. Day-Lewis, and V.L. Freedman. 2022. "Integration of Large-Scale Electrical Imaging into Geological Framework Development and Refinement." Environmental Processes 9, no. 2:Art. No. 21. PNNL-SA-166767. doi:10.1007/s40710-022-00570-2
  • Singha K., T.C. Johnson, F.D. Day-Lewis, and L. Slater. 2022. "Electrical Imaging for Hydrogeology." In Groundwater Geophysics. Guelph:The Groundwater Project. PNNL-SA-159896.


  • Shapiro A.M., and F.D. Day-Lewis. 2021. "Estimating and Forecasting Time-Varying Groundwater Recharge in Fractured Rock: A State-Space Formulation with Preferential and Diffuse Flow to the Water Table." Water Resources Research 57, no. 9:Article No. e2020WR029110. PNNL-SA-165293. doi:10.1029/2020WR029110


  • Johnson T.C., R. Versteeg, F.D. Day-Lewis, W. Major, and J.W. Lane. 2015. "Time-Lapse Electrical Geophysical Monitoring of Amendment-Based Biostimulation." Groundwater 53, no. 6:920-932. PNNL-SA-115558. doi:10.1111/gwat.12291
  • Singha K., F.D. Day-Lewis, T.C. Johnson, and L.D. Slater. 2015. "Advances in interpretation of subsurface processes with time-lapse electrical imaging." Hydrological Processes 29, no. 6:1549-1576. PNNL-SA-110809. doi:10.1002/hyp.10280


  • Johnson T.C., L. Slater, D. Ntarlagiannis, F.D. Day-Lewis, and M. Elwaseif. 2012. "Monitoring groundwater-surface water interaction using time-series and time-frequency analysis of transient three-dimensional electrical resistivity changes." Water Resources Research 48. PNNL-SA-85275. doi:10.1029/2012WR011893


  • Johnson T.C., R.J. Versteeg, A.L. Ward, F.D. Day-Lewis, and A. Revil. 2010. "Improved hydrogeophysical characterization and monitoring through parallel modeling and inversion of time-domain resistivity andinduced-polarization data." Geophysics 75, no. 4:WA27-WA41. PNNL-SA-69316. doi:10.1190/1.3475513
  • Slater L., D. Ntarlagiannis, F.D. Day-Lewis, K. Mwakanyamale, R.J. Versteeg, A.L. Ward, and C.E. Strickland, et al. 2010. "Use of Electrical Imaging and Distributed Temperature Sensing Methods to Characterize Surface Water-Groundwater Exchange Regulating Uranium Transport at the Hanford 300 Area, Washington." Water Resources Research 46, no. 10:Paper No. W10533. PNNL-SA-69319. doi:10.1029/2010WR009110