Todd Caldwell is a research hydrologist in the Nevada Water Science Center in Carson City, NV.
Todd specializes in field investigations and numerical modeling of unsaturated zone processes and remotely-sensed soil moisture. His research focuses on in situ soil moisture and evapotranspiration monitoring, near-surface geophysics, and scaling hydraulic properties of soils and sediments.
Professional Experience
2019 - pres: Hydrologist, USGS Nevada Water Science Center
2012 - 2019: Research Scientist, Bureau of Economic Geology, University of Texas at Austin
2001 - 2012: Research Professor, Desert Research Institute, Reno, NV
2000 - 2001: Hydrologist, Pacific Northwest National Lab, Richland, WA
Education and Certifications
Ph.D., Hydrogeology, University of Nevada, Reno
M.S., Hydrogeology, University of Nevada, Reno
B.S., Earth and Planetary Sciences, University of New Mexico
Science and Products
Quantifying watershed controls on fine sediment particles and nutrient loading to Lake Tahoe using data mining and machine learning
Since the late 1980’s, the USGS has collected discharge, sediment, and water quality data at seven major drainages under the Lake Tahoe Interagency Monitoring Program (LTIMP). Recently, continuous, real-time measurements of turbidity were added to the LTIMP. These data can be combined with in situ, model simulations, and remotely-sensed datasets available from the USGS, National Aeronautics and...
Daily average soil moisture and ancillary data from the Noah land surface model in the National Land Data Assimilation version 2 extracted for GAGES-II watersheds, 1980 to 2020
This U.S Geological Survey data release contains soil moisture, actual evapotranspiration, precipitation, and potential evapotranspiration by watershed for the United States from 1980 to 2020. Hourly values from NASA's North American Land Data Assimilation System Phase 2 (NLDAS-2) Noah model were aggregated to daily values and extracted by Geospatial Attributes of Gages for Evaluating Streamflow,
U.S. Streamflow Drought During the Last Century: annual drought and low flow metrics, annual climate, and trends for the periods 1921-2020, 1951-2020 and 1981-2020
This dataset contains annual flow metrics quantifying drought and low streamflows for USGS GAGES-2 gages in the contiguous U.S. satisfying data completeness checks for the periods 1921-2020, 1951-2020, and 1981-2020. The dataset also contains annual climate variables from the USGS Monthly Water Balance Model (MWBM). The dataset provides trend analysis outputs for annual drought and low flow metric
Documentation of VS2DH Seepage Models: Surface Infiltration and Unsaturated Zone Characterization in Support of Managed Aquifer Recharge, Washoe County, Nevada
Two-dimensional variably saturated heat and flow models (VS2DH) were used to examine seepage rates along the Birdspring drainage for the purpose of exploring the drainage channel for use in an managed aquifer recharge project. Six transect models were separately calibrated to sediment temperatures observed during episodic runoff events during water year 2017 and 2018. The models were calibrated to
Supplemental Data: Surface Infiltration and Unsaturated Zone Characterization in Support of Managed Aquifer Recharge in Bedell Flat, Washoe County, Nevada
This USGS data release presents tabular data and photos used to determine (1) the duration of flow, subsurface temperature, and concurrent infiltration along an ephemeral channel and (2) vertical change of soil moisture, texture, and pore-water chemistry in the unsaturated zone at selected locations. The data were collected to investigate the feasibility of managed aquifer recharge (MAR) for aquif
Evolving radon diffusion through earthen barriers at uranium waste disposal sites
Field measurements of Rn-222 fluxes from the tops and bottoms of compacted clay radon barriers were used to calculate effective Rn diffusion coefficients (DRn) at four uranium waste disposal sites in the western United States to assess cover performance after more than 20 years of service. Values of DRn ranged from 7.4 × 10−7 to 6.0 × 10−9 m2/s, averaging 1.42 × 10−7. Water saturation (SW) from so
Authors
Mark Fuhrmann, Todd Caldwell, William J. Likos, W. Jodi Waugh, Morgan M. Williams, Craig H. Benson
Working toward a National Coordinated Soil Moisture Monitoring Network: Vision, progress, and future directions
Soil moisture is a critical land surface variable, impacting the water, energy, and carbon cycles. While in situ soil moisture monitoring networks are still developing, there is no cohesive strategy or framework to coordinate, integrate, or disseminate these diverse data sources in a synergistic way that can improve our ability to understand climate variability at the national, state, and local le
Authors
C. Bruce Baker, Michael H. Cosh, John Bolten, Mark Brusberg, Todd Caldwell, Stephanie Connolly, Iliyana Dobreva, Nathan Edwards, Peter E. Goble, Tyson E. Ochsner, Steven M. Quiring, Michael Robotham, Marina Skumanich, Mark Svoboda, W. Alex White, Molly Woloszyn
In situ soil moisture sensors in undisturbed soils
Soil moisture directly affects operational hydrology, food security, ecosystem services, and the climate system. However, the adoption of soil moisture data has been slow due to inconsistent data collection, poor standardization, and typically short record duration. Soil moisture, or quantitatively volumetric soil water content (SWC), is measured using buried, in situ sensors that infer SWC from a
Authors
Todd Caldwell, Michael H. Cosh, Steven R. Evett, Nathan Edwards, Heather Hofman, Bradley Illston, Tilden P. Meyers, Marina Skumanich, Kent Sutcliffe
Basis for technical guidance to evaluate evapotranspiration covers
This report provides technical guidance to evaluate evapotranspiration (ET) cover design criteria with emphasis on applications to long-term disposal sites such as Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA) sites. Water balance covers, also known as ET covers, reduce percolation by storing precipitation then allowing vegetation to cycle it back to the atmosphere. For long-term (o
Authors
Todd Caldwell, Jena Huntington, Gwendolyn Elizabeth Davies, S. Tabatabai, M. Fuhrmann
Going beyond low flows: Streamflow drought deficit and duration illuminate distinct spatiotemporal drought patterns and trends in the U.S. during the last century
Streamflow drought is a recurring challenge, and understanding spatiotemporal patterns of past droughts is needed to manage future water resources. We examined regional patterns in streamflow drought metrics and compared these metrics to low flow timing and magnitude using long-term daily records for 555 minimally disturbed watersheds. For each streamgage, we calculated streamflow drought duration
Authors
John C. Hammond, Caelan E. Simeone, Jory Seth Hecht, Glenn A. Hodgkins, Melissa Lombard, Gregory J. McCabe, David M. Wolock, Michael Wieczorek, Carolyn G Olson, Todd Caldwell, Robert W. Dudley, Adam N. Price
Evapotranspiration covers at uranium mill tailings sites
Waste isolation is a key strategy for mitigating risk from municipal solid waste (MSW) and hazardous waste streams. Conventional covers at MSW facilities are designed for a 30-yr post-closure period where compacted soils and geosynthetics are used to minimize percolation into buried waste. Recently, evapotranspiration (ET) covers have shown beneficial use for MSW management. Evapotranspiration cov
Authors
Todd Caldwell, Sarah Tabatabai, Jena Huntington, Gwendolyn Elizabeth Davies, Mark Fuhrmann
Surface infiltration and unsaturated zone characterization in support of managed aquifer recharge in Bedell Flat, Washoe County, Nevada
Aquifer storage and recovery (ASR) expands the portfolio of public water supply and improves resiliency to drought and future water demand. This study investigated the feasibility of ASR in the Bedell Flat Hydrographic Area using land-based methods including in-channel managed aquifer recharge (MAR) and rapid infiltration basins (RIB). Bedell Flat, one of two flow-through groundwater basins near R
Authors
Todd Caldwell, Ramon C. Naranjo, David Smith, Christian Kropf
Developing a strategy for the national coordinated soil moisture monitoring network
Soil moisture is a critical land surface variable, affecting a wide variety of climatological, agricultural, and hydrological processes. Determining the current soil moisture status is possible via a variety of methods, including in situ monitoring, remote sensing, and numerical modeling. Although all of these approaches are rapidly evolving, there is no cohesive strategy or framework to integrate
Authors
Micheal Cosh, Todd Caldwell, Bruce M. Baker, John D. Bolton, Nathan Edwards, Peter Goble, Heather Hofman, Tyson Ochsner, Steven Quiring, Charles W. Schalk, Marina Skumanich, Mark Svoboda, Molly Woloszyn
Soil moisture product validation good practices protocol, version 1.0
The Global Climate Observing System (GCOS) included soil moisture in the list of Essential
Climate Variables (ECVs) to express its important role in Earth’s water, energy and carbon cycle.
Soil moisture has a major impact on agriculture, land surface hydrology, weather, and climate
forecasting. This document is a community-based effort to provide recommendations on good
practices for the validatio
Authors
Carsten Montzka, Michael H. Cosh, Bagher Bayat, Ahmad Al Bitar, Aaron Berg, Rajat Bindlish, Heye Reemt Bogena, John D. Bolton, Francois Cabot, Todd Caldwell, Steven Chan, Andreas Colliander, Wade Crow, Narendra Das, Gabrielle De Lannoy, Wouter Dorigo, Steven R. Evett, Alexander Gruber, Sebastian Hahn, Thomas Jagdhuber, Scott F. Jones, Yann Kerr, Seung-bum Kim, Christian Koyama, Mehmed Kurum, Ernesto Lopez-Baeza, Francesco Mattia, Kaighin A. McColl, Susanne Mecklenburg, Binayak Mohanty, Peggy O´Neill, Dani Or, Thierry Pellarin, George P. Petropoulos, Maria Piles, Rolf H. Reichle, Nemesio Rodriguez-Fernandez, Christoph Rüdiger, Tracy Scanlon, Robert C. Schwartz, Daniel Spengler, Prashant K. Srivastava, Swati Suman, Robin van der Schalie, Wolfgang Wagner, Urs Wegmüller, Jean-Pierre Wigneron, Fernando Camacho, Jaime Nickeson
Uncertainty of reference pixel soil moisture averages sampled at SMAP core validation sites
Despite extensive efforts to maximize ground coverage and improve upscaling functions within core validation sites (CVS) of the NASA Soil Moisture Active/Passive (SMAP) mission, spatial averages of point-scale soil moisture observations often fail to accurately capture the true average of the reference pixels. Therefore, some level of pixel-scale sampling error from in situ observations must be co
Authors
Fan Chen, W.T Crow, M.H. Cosh, A. Colliander, J. Asanuma, A. Berg, D.D. Bosch, Todd Caldwell, C. Holifield-Collins, J. Martínez-Fernández, H. McNairn, P.J. Starks, Z. Su, J.P. Walker
Non-USGS Publications**
Caldwell, T. G., B. D. Wolaver, T. Bongiovanni, J. P. Pierre, S. Robertson, C. Abolt, and B. R. Scanlon (2020), Spring discharge and thermal regime of a groundwater dependent ecosystem in an arid karst environment, Journal of Hydrology, 10.1016/j.jhydrol.2020.124947.
Colliander, A., T. J. Jackson, A. Berg, D. D. Bosch, T. Caldwell, S. Chan, M. H. Cosh, C. H. Collins, J. Martínez-Fernández, H. McNairn, J. H. Prueger, P. J. Starks, J. P. Walker, and S. H. Yueh (2020), Effect of Rainfall Events on SMAP Radiometer-Based Soil Moisture Accuracy Using Core Validation Sites, Journal of Hydrometeorology, 21, 255-264, 10.1175/jhm-d-19-0122.1.
Chaubell, M. J., J. Asanuma, A. A. Berg, D. D. Bosch, T. Caldwell, M. H. Cosh, C. H. Collins, J. Martinez-Fernandez, M. Seyfried, P. J. Starks, Z. Su, S. H. Yueh, M. Thibeault, J. Walker, R. S. Dunbar, A. Colliander, F. Chen, S. K. Chan, D. Entekhabi, R. Bindlish, and P. E. O'Neill (2020), Improved SMAP Dual-Channel Algorithm for the Retrieval of Soil Moisture, IEEE Transactions on Geoscience and Remote Sensing, 1-12, doi: 10.1109/tgrs.2019.2959239.
Gholoubi, A., H. Emami, and T. Caldwell (2019), Deforestation effects on soil aggregate stability quantified by the high energy moisture characteristic method, Geoderma, 355, 113919, 10.1016/j.geoderma.2019.113919.
Mayes, K. B., G. R. Wilde, M. E. McGarrity, B. Wolaver, and T. G. Caldwell (2019), Watershed-Scale Conservation of Native Fishes in the Brazos River Basin, Texas, in Multispecies and Watershed Approaches to Freshwater Fish Conservation, edited by D. C. Dauwalter, T. Birdson and G. P. Garret, pp. 315–343, American Fisheries Society Symposia 91, Bethesda, MD.
Robertson, S., B. Wolaver, T. G. Caldwell, T. Birdson, R. Smith, T. Hardy, J. Lewey, and J. Joplin (2019), A multidisciplinary approach to developing the science and public support needed to maintain instream flows in the Devils River Basin, Texas, in Multispecies and Watershed Approaches to Freshwater Fish Conservation, edited by D. C. Dauwalter, T. Birdson and G. P. Garret, pp. 293–314, American Fisheries Society Symposia 91, Bethesda, MD.
Das, N. N., D. Entekhabi, R. S. Dunbar, M. J. Chaubell, A. Colliander, S. Yueh, T. Jagdhuber, F. Chen, W. Crow, P. E. O'Neill, J. P. Walker, A. Berg, D. D. Bosch, T. Caldwell, M. H. Cosh, C. H. Collins, E. Lopez-Baeza, and M. Thibeault (2019), The SMAP and Copernicus Sentinel 1A/B microwave active-passive high resolution surface soil moisture product, Remote Sensing of Environment, 233, 111380, 10.1016/j.rse.2019.111380.
Caldwell, T. G., T. Bongiovanni, M. H. Cosh, T. J. Jackson, A. Colliander, C. J. Abolt, R. Casteel, T. Larson, B. R. Scanlon, and M. H. Young (2019), The Texas Soil Observation Network: A comprehensive soil moisture dataset for remote sensing and land surface model validation, Vadose Zone Journal, 18:100034, doi:10.2136/vzj2019.04.0034.
Sun, A. Y., Y. L. Xia, T. G. Caldwell, and Z. C. Hao (2018), Patterns of precipitation and soil moisture extremes in Texas, US: A complex network analysis, Advances in Water Resources, 112, 203-213, 10.1016/j.advwatres.2017.12.019.
Kolassa, J., R. H. Reichle, Q. Liu, S. H. Alemohammad, P. Gentine, K. Aida, J. Asanuma, S. Bircher, T. Caldwell, A. Colliander, M. Cosh, C. Holifield Collins, T. J. Jackson, J. Martínez-Fernández, H. McNairn, A. Pacheco, M. Thibeault, and J. P. Walker (2018), Estimating surface soil moisture from SMAP observations using a Neural Network technique, Remote Sensing of Environment, 204, 43-59, doi: 10.1016/j.rse.2017.10.045.
Das, N. N., D. Entekhabi, R. S. Dunbar, A. Colliander, F. Chen, W. Crow, T. J. Jackson, A. Berg, D. D. Bosch, T. Caldwell, M. H. Cosh, C. H. Collins, E. Lopez-Baeza, M. Moghaddam, T. Rowlandson, P. J. Starks, M. Thibeault, J. P. Walker, X. L. Wu, P. E. O'Neill, S. Yueh, and E. G. Njoku (2018), The SMAP mission combined active-passive soil moisture product at 9 km and 3 km spatial resolutions, Remote Sensing of Environment, 211, 204-217, doi:10.1016/j.rse.2018.04.011.
Colliander, A., T. J. Jackson, S. K. Chan, P. O'Neill, R. Bindlish, M. H. Cosh, T. Caldwell, J. P. Walker, A. Berg, H. McNairn, M. Thibeault, J. Martinez-Fernandez, K. H. Jensen, J. Asanuma, M. S. Seyfried, D. D. Bosch, P. J. Starks, C. H. Collins, J. H. Prueger, Z. Su, E. Lopez-Baeza, and S. H. Yueh (2018), An assessment of the differences between spatial resolution and grid size for the SMAP enhanced soil moisture product over homogeneous sites, Remote Sensing of Environment, 207, 65-70, doi:10.1016/j.rse.2018.02.006.
Chan, S. K., R. Bindlish, P. O'Neill, T. Jackson, E. Njoku, S. Dunbar, J. Chaubell, J. Piepmeier, S. Yueh, D. Entekhabi, A. Colliander, F. Chen, M. H. Cosh, T. Caldwell, J. Walker, A. Berg, H. McNairn, M. Thibeault, J. Martinez-Fernandez, F. Uldall, M. Seyfried, D. Bosch, P. Starks, C. H. Collins, J. Prueger, R. van der Velde, J. Asanuma, M. Palecki, E. E. Small, M. Zreda, J. Calvet, W. T. Crow, and Y. Kerr (2018), Development and assessment of the SMAP enhanced passive soil moisture product, Remote Sensing of Environment, 204, 931-941, doi: 10.1016/j.rse.2017.08.025.
Caldwell, T. G., T. Bongiovanni, M. H. Cosh, C. Halley, and M. H. Young (2018), Field and laboratory evaluation of the CS655 soil water content sensor, Vadose Zone Journal, 17, 170214, doi:10.2136/vzj2017.12.0214.
Bindlish, R., M. H. Cosh, T. J. Jackson, T. Koike, H. Fujii, S. K. Chan, J. Asanuma, A. Berg, D. D. Bosch, T. Caldwell, C. H. Collins, H. McNairn, J. Martinez-Fernandez, J. Prueger, T. Rowlandson, M. Seyfried, P. Starks, M. Thibeault, R. Van der Velde, J. P. Walker, and E. J. Coopersmith (2018), GCOM-W AMSR2 soil moisture product validation using core validation sites, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 11, 209-219, doi:10.1109/Jstars.2017.2754293.
Abolt, C., T. Caldwell, B. Wolaver, and H. Pai (2018), Unmanned aerial vehicle-based monitoring of groundwater inputs to surface waters using an economical thermal infrared camera, Optical Engineering, 57, 9, 053113, doi:10.1117/1.Oe.57.5.053113.
Young, M. H., J. H. Andrews, T. G. Caldwell, and K. Saylam (2017), Airborne LiDAR and Aerial Imagery to Assess Potential Burrow Locations for the Desert Tortoise (Gopherus agassizii), Remote Sensing, 9, ARTN 458, doi:10.3390/rs9050458.
Reichle, R. H., G. J. M. De Lannoy, Q. Liu, J. V. Ardizzone, A. Colliander, A. Conaty, W. Crow, T. J. Jackson, L. A. Jones, J. S. Kimball, R. D. Koster, S. P. Mahanama, E. B. Smith, A. Berg, S. Bircher, D. Bosch, T. G. Caldwell, M. Cosh, A. Gonzalez-Zamora, C. D. H. Collins, K. H. Jensen, S. Livingston, E. Lopez-Baeza, J. Martinez-Fernandez, H. McNairn, M. Moghaddam, A. Pacheco, T. Pellarin, J. Prueger, T. Rowlandson, M. Seyfried, P. Starks, Z. B. Su, M. Thibeault, R. van der Velde, J. Walker, X. L. Wu, and Y. J. Zeng (2017), Assessment of the SMAP Level-4 Surface and Root-Zone Soil Moisture Product Using In Situ Measurements, Journal of Hydrometeorology, 18, 2621-2645, 10.1175/Jhm-D-17-0063.1.
Ouellette, J. D., J. T. Johnson, A. Balenzano, F. Mattia, G. Satalino, S.-B. Kim, R. S. Dunbar, A. Colliander, M. H. Cosh, T. G. Caldwell, J. P. Walker, and A. A. Berg (2017), A time-series approach to estimating soil moisture from vegetated surfaces using L-band radar backscatter, IEEE Transactions on Geoscience and Remote Sensing, 55, 3186-3193, doi:10.1109/TGRS.2017.2663768.
Kolassa, J., R. Reichle, Q. Liu, M. Cosh, D. Bosch, T. Caldwell, A. Colliander, C. Holifield Collins, T. Jackson, S. Livingston, M. Moghaddam, and P. Starks (2017), Data assimilation to extract soil moisture information from SMAP observations, Remote Sensing, 1179, doi:10.3390/rs9111179, 1179, doi:10.3390/rs9111179.
Kim, S. B., J. J. van Zyl, J. T. Johnson, M. Moghaddam, L. Tsang, A. Colliander, R. S. Dunbar, T. J. Jackson, S. Jaruwatanadilok, R. West, A. Berg, T. Caldwell, M. H. Cosh, D. C. Goodrich, S. Livingston, E. Lopez-Baeza, T. Rowlandson, M. Thibeault, J. P. Walker, D. Entekhabi, E. G. Njoku, P. E. O'Neill, and S. H. Yueh (2017), Surface soil moisture retrieval using the L-band synthetic aperture radar onboard the Soil Moisture Active-Passive satellite and evaluation at core validation sites, IEEE Transactions on Geoscience and Remote Sensing, 55, 1897-1914, doi:10.1109/Tgrs.2016.2631126.
Degre, A., M. J. van der Ploeg, T. Caldwell, and H. P. A. Gooren (2017), Comparison of Soil Water Potential Sensors: A Drying Experiment, Vadose Zone Journal, 16, 10.2136/vzj2016.08.0067.
Colliander, A., T. J. Jackson, R. Bindlish, S. Chan, N. Das, S. B. Kim, M. H. Cosh, R. S. Dunbar, L. Dang, L. Pashaian, J. Asanuma, K. Aida, A. Berg, T. Rowlandson, D. Bosch, T. Caldwell, K. Caylor, D. Goodrich, H. al Jassar, E. Lopez-Baeza, J. Martinez-Fernandez, A. Gonzalez-Zamora, S. Livingston, H. McNairn, A. Pacheco, M. Moghaddam, C. Montzka, C. Notarnicola, G. Niedrist, T. Pellarin, J. Prueger, J. Pulliainen, K. Rautiainen, J. Ramos, M. Seyfried, P. Starks, Z. Su, Y. Zeng, R. van der Velde, M. Thibeault, W. Dorigo, M. Vreugdenhil, J. P. Walker, X. Wu, A. Monerris, P. E. O'Neill, D. Entekhabi, E. G. Njoku, and S. Yueh (2017), Validation of SMAP surface soil moisture products with core validation sites, Remote Sensing of Environment, 191, 215-231, doi:10.1016/j.rse.2017.01.021.
Clewley, D., J. B. Whitcomb, R. Akbar, A. R. Silva, A. Berg, J. R. Adams, T. Caldwell, D. Entekhabi, and M. Moghaddam (2017), A method for upscaling in situ soil moisture measurements to satellite footprint scale using random forests, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10, 2663-2673.
Abolt, C. J., M. H. Young, and T. G. Caldwell (2017), Numerical Modelling of Ice-Wedge Polygon Geomorphic Transition, Permafrost and Periglacial Processes, 28, 347-355.
Shellito, P. J., E. E. Small, A. Colliander, R. Bindlish, M. H. Cosh, A. A. Berg, D. D. Bosch, T. G. Caldwell, D. C. Goodrich, H. McNairn, J. H. Prueger, P. J. Starks, R. van der Velde, and J. P. Walker (2016), SMAP soil moisture drying more rapid than observed in situ following rainfall events, Geophysical Research Letters, 43, 8068-8075, 10.1002/2016gl069946.
Chan, S. K., R. Bindlish, P. E. O'Neill, E. Njoku, T. Jackson, A. Colliander, F. Chen, M. Burgin, S. Dunbar, J. Piepmeier, S. Yueh, D. Entekhabi, M. H. Cosh, T. Caldwell, J. Walker, X. L. Wu, A. Berg, T. Rowlandson, A. Pacheco, H. McNairn, M. Thibeault, J. Martinez-Fernandez, A. Gonzalez-Zamora, M. Seyfried, D. Bosch, P. Starks, D. Goodrich, J. Prueger, M. Palecki, E. E. Small, M. Zreda, J. C. Calvet, W. T. Crow, and Y. Kerr (2016), Assessment of the SMAP passive soil moisture product, IEEE Transactions on Geoscience and Remote Sensing, 54, 4994-5007.
Zhu, J. T., D. M. Sun, M. H. Young, T. G. Caldwell, and F. Pan (2015), Shrub spatial organization and partitioning of evaporation and transpiration in arid environments, Ecohydrology, 8, 1218-1228.
Rau, B. M., J. C. Chambers, D. A. Pyke, B. A. Roundy, E. W. Schupp, P. Doescher, and T. G. Caldwell (2014), Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems, Rangeland Ecology & Management, 67, 506-521.
Caldwell, T. G., T. Wohling, M. H. Young, D. P. Boyle, and E. V. McDonald (2013), Characterizing Disturbed Desert Soils Using Multiobjective Parameter Optimization, Vadose Zone Journal, 12, 1-23.
Wilcox, B. P., L. Turnbull, M. H. Young, C. J. Williams, S. Ravi, M. S. Seyfried, D. R. Bowling, R. L. Scott, M. J. Germino, T. G. Caldwell, and J. Wainwright (2012), Invasion of shrublands by exotic grasses: ecohydrological consequences in cold versus warm deserts, Ecohydrology, 5, 160-173, 10.1002/eco.247.
Flerchinger, G. N., T. G. Caldwell, J. Cho, and S. P. Hardegree (2012), Simultaneous Heat and Water (Shaw) Model: Model Use, Calibration, and Validation, Transactions of the ASABE, 55, 1395-1411.
Caldwell, T. G., M. H. Young, E. V. McDonald, and J. T. Zhu (2012), Soil heterogeneity in Mojave Desert shrublands: Biotic and abiotic processes, Water Resources Research, 48, W09551, doi: 10.1029/2012wr011963.
Rau, B. M., D. W. Johnson, R. R. Blank, R. J. Tausch, B. A. Roundy, R. F. Miller, T. G. Caldwell, and A. Lucchesi (2011), Woodland expansion’s influence on belowground carbon and nitrogen in the Great Basin U.S, Journal of Arid Environments, 75, 827-835.
Rau, B. M., D. W. Johnson, R. R. Blank, A. Lucchesi, T. G. Caldwell, and E. W. Schupp (2011), Transition From Sagebrush Steppe to Annual Grass (Bromus tectorum): Influence on Belowground Carbon and Nitrogen, Rangeland Ecology & Management, 64, 139-147.
Bacon, S. N., E. V. McDonald, T. G. Caldwell, and G. K. Dalldorf (2010), Timing and distribution of alluvial fan sedimentation in response to strengthening of late Holocene ENSO variability in the Sonoran Desert, southwestern Arizona, USA, Quaternary Research, 73, 425-438.
Young, M. H., T. G. Caldwell, D. G. Meadows, and L. F. Fenstermaker (2009), Variability of soil physical and hydraulic properties at the Mojave Global Change Facility, Nevada: Implications for water budget and evapotranspiration, Journal of Arid Environments, 73, 733-744.
Caldwell, T. G., E. V. McDonald, and M. H. Young (2009), The seedbed microclimate and active revegetation of disturbed lands in the Mojave Desert, Journal of Arid Environments, 73, 563-573.
Caldwell, T. G., D. W. Johnson, W. W. Miller, R. G. Qualls, and R. R. Blank (2009), Prescription Fire and Anion Retention in Tahoe Forest Soils, Soil Science, 174, 594-600.
McDonald, E. V., and T. G. Caldwell (2008), Geochemical characteristics of Iraqi dust and soil samples and related impacts to weapon malfunctions, in Military Geography and Geology: History and Technology, edited by C. P. Nathanail, R. J. Abrahart and R. P. Bradshaw, pp. 258-265, Land Quality Press, Nottingham.
Caldwell, T. G., M. H. Young, J. T. Zhu, and E. V. McDonald (2008), Spatial structure of hydraulic properties from canopy to interspace in the Mojave Desert, Geophysical Research Letters, 35, L19406, doi:10.1029/2008gl035095.
Caldwell, T. G., E. V. McDonald, S. N. Bacon, and G. Stullenbarger (2008), The performance and sustainability of vehicle dust courses for military testing, Journal Of Terramechanics, 45, 213-221.
Bacon, S. N., E. V. McDonald, S. E. Baker, T. G. Caldwell, and G. Stullenbarger (2008), Desert terrain characterization of landforms and surface materials within vehicle test courses at US Army Yuma Proving Ground, USA, Journal Of Terramechanics, 45, 167-183.
Shafer, D. S., M. H. Young, S. F. Zitzer, T. G. Caldwell, and E. V. McDonald (2007), Impacts of interrelated biotic and abiotic processes during the past 125 000 years of landscape evolution in the Northern Mojave Desert, Nevada, USA, Journal of Arid Environments, 69, 633-657.
Caldwell, T. G., E. V. McDonald, and M. H. Young (2006), Soil disturbance and hydrologic response at the National Training Center, Ft. Irwin, California, Journal of Arid Environments, 67, 456-472.
Young, M. H., E. V. McDonald, T. G. Caldwell, S. G. Benner, and D. G. Meadows (2005), Hydraulic properties of a desert soil chronosequence in the Mojave desert, USA, Vadose Zone Journal, 3, 956-963.
Johnson, D. W., J. F. Murphy, R. B. Susfalk, T. G. Caldwell, W. W. Miller, R. F. Walker, and R. F. Powers (2005), The effects of wildfire, salvage logging, and post-fire N-fixation on the nutrient budgets of a Sierran forest, Forest Ecology And Management, 220, 155-165.
Sisson, J. B., G. W. Gee, J. M. Hubbell, W. L. Bratton, J. C. Ritter, A. L. Ward, and T. G. Caldwell (2002), Advances in Tensiometry for Long-Term Monitoring of Soil Water Pressures, Vadose Zone Journal, 1, 310-315.
Gee, G. W., A. L. Ward, T. G. Caldwell, and J. C. Ritter (2002), A vadose zone water fluxmeter with divergence control, Water Resources Research, 38, ARTN 1141, doi:10.1029/2001wr000816.
Caldwell, T. G., D. W. Johnson, W. W. Miller, and R. G. Qualls (2002), Forest floor carbon and nitrogen losses due to prescription fire, Soil Science Society of America Journal, 66, 262-267.
Johnson, D. W., R. B. Susfalk, R. A. Dahlgren, T. G. Caldwell, and W. W. Miller (2001), Nutrient fluxes in a snow-dominated, semi-arid forest: Spatial and temporal patterns, Biogeochemistry, 55, 219-245.
**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
- Science
Quantifying watershed controls on fine sediment particles and nutrient loading to Lake Tahoe using data mining and machine learning
Since the late 1980’s, the USGS has collected discharge, sediment, and water quality data at seven major drainages under the Lake Tahoe Interagency Monitoring Program (LTIMP). Recently, continuous, real-time measurements of turbidity were added to the LTIMP. These data can be combined with in situ, model simulations, and remotely-sensed datasets available from the USGS, National Aeronautics and... - Data
Daily average soil moisture and ancillary data from the Noah land surface model in the National Land Data Assimilation version 2 extracted for GAGES-II watersheds, 1980 to 2020
This U.S Geological Survey data release contains soil moisture, actual evapotranspiration, precipitation, and potential evapotranspiration by watershed for the United States from 1980 to 2020. Hourly values from NASA's North American Land Data Assimilation System Phase 2 (NLDAS-2) Noah model were aggregated to daily values and extracted by Geospatial Attributes of Gages for Evaluating Streamflow,U.S. Streamflow Drought During the Last Century: annual drought and low flow metrics, annual climate, and trends for the periods 1921-2020, 1951-2020 and 1981-2020
This dataset contains annual flow metrics quantifying drought and low streamflows for USGS GAGES-2 gages in the contiguous U.S. satisfying data completeness checks for the periods 1921-2020, 1951-2020, and 1981-2020. The dataset also contains annual climate variables from the USGS Monthly Water Balance Model (MWBM). The dataset provides trend analysis outputs for annual drought and low flow metricDocumentation of VS2DH Seepage Models: Surface Infiltration and Unsaturated Zone Characterization in Support of Managed Aquifer Recharge, Washoe County, Nevada
Two-dimensional variably saturated heat and flow models (VS2DH) were used to examine seepage rates along the Birdspring drainage for the purpose of exploring the drainage channel for use in an managed aquifer recharge project. Six transect models were separately calibrated to sediment temperatures observed during episodic runoff events during water year 2017 and 2018. The models were calibrated toSupplemental Data: Surface Infiltration and Unsaturated Zone Characterization in Support of Managed Aquifer Recharge in Bedell Flat, Washoe County, Nevada
This USGS data release presents tabular data and photos used to determine (1) the duration of flow, subsurface temperature, and concurrent infiltration along an ephemeral channel and (2) vertical change of soil moisture, texture, and pore-water chemistry in the unsaturated zone at selected locations. The data were collected to investigate the feasibility of managed aquifer recharge (MAR) for aquif - Publications
Evolving radon diffusion through earthen barriers at uranium waste disposal sites
Field measurements of Rn-222 fluxes from the tops and bottoms of compacted clay radon barriers were used to calculate effective Rn diffusion coefficients (DRn) at four uranium waste disposal sites in the western United States to assess cover performance after more than 20 years of service. Values of DRn ranged from 7.4 × 10−7 to 6.0 × 10−9 m2/s, averaging 1.42 × 10−7. Water saturation (SW) from soAuthorsMark Fuhrmann, Todd Caldwell, William J. Likos, W. Jodi Waugh, Morgan M. Williams, Craig H. BensonWorking toward a National Coordinated Soil Moisture Monitoring Network: Vision, progress, and future directions
Soil moisture is a critical land surface variable, impacting the water, energy, and carbon cycles. While in situ soil moisture monitoring networks are still developing, there is no cohesive strategy or framework to coordinate, integrate, or disseminate these diverse data sources in a synergistic way that can improve our ability to understand climate variability at the national, state, and local leAuthorsC. Bruce Baker, Michael H. Cosh, John Bolten, Mark Brusberg, Todd Caldwell, Stephanie Connolly, Iliyana Dobreva, Nathan Edwards, Peter E. Goble, Tyson E. Ochsner, Steven M. Quiring, Michael Robotham, Marina Skumanich, Mark Svoboda, W. Alex White, Molly WoloszynIn situ soil moisture sensors in undisturbed soils
Soil moisture directly affects operational hydrology, food security, ecosystem services, and the climate system. However, the adoption of soil moisture data has been slow due to inconsistent data collection, poor standardization, and typically short record duration. Soil moisture, or quantitatively volumetric soil water content (SWC), is measured using buried, in situ sensors that infer SWC from aAuthorsTodd Caldwell, Michael H. Cosh, Steven R. Evett, Nathan Edwards, Heather Hofman, Bradley Illston, Tilden P. Meyers, Marina Skumanich, Kent SutcliffeBasis for technical guidance to evaluate evapotranspiration covers
This report provides technical guidance to evaluate evapotranspiration (ET) cover design criteria with emphasis on applications to long-term disposal sites such as Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA) sites. Water balance covers, also known as ET covers, reduce percolation by storing precipitation then allowing vegetation to cycle it back to the atmosphere. For long-term (oAuthorsTodd Caldwell, Jena Huntington, Gwendolyn Elizabeth Davies, S. Tabatabai, M. FuhrmannGoing beyond low flows: Streamflow drought deficit and duration illuminate distinct spatiotemporal drought patterns and trends in the U.S. during the last century
Streamflow drought is a recurring challenge, and understanding spatiotemporal patterns of past droughts is needed to manage future water resources. We examined regional patterns in streamflow drought metrics and compared these metrics to low flow timing and magnitude using long-term daily records for 555 minimally disturbed watersheds. For each streamgage, we calculated streamflow drought durationAuthorsJohn C. Hammond, Caelan E. Simeone, Jory Seth Hecht, Glenn A. Hodgkins, Melissa Lombard, Gregory J. McCabe, David M. Wolock, Michael Wieczorek, Carolyn G Olson, Todd Caldwell, Robert W. Dudley, Adam N. PriceEvapotranspiration covers at uranium mill tailings sites
Waste isolation is a key strategy for mitigating risk from municipal solid waste (MSW) and hazardous waste streams. Conventional covers at MSW facilities are designed for a 30-yr post-closure period where compacted soils and geosynthetics are used to minimize percolation into buried waste. Recently, evapotranspiration (ET) covers have shown beneficial use for MSW management. Evapotranspiration covAuthorsTodd Caldwell, Sarah Tabatabai, Jena Huntington, Gwendolyn Elizabeth Davies, Mark FuhrmannSurface infiltration and unsaturated zone characterization in support of managed aquifer recharge in Bedell Flat, Washoe County, Nevada
Aquifer storage and recovery (ASR) expands the portfolio of public water supply and improves resiliency to drought and future water demand. This study investigated the feasibility of ASR in the Bedell Flat Hydrographic Area using land-based methods including in-channel managed aquifer recharge (MAR) and rapid infiltration basins (RIB). Bedell Flat, one of two flow-through groundwater basins near RAuthorsTodd Caldwell, Ramon C. Naranjo, David Smith, Christian KropfDeveloping a strategy for the national coordinated soil moisture monitoring network
Soil moisture is a critical land surface variable, affecting a wide variety of climatological, agricultural, and hydrological processes. Determining the current soil moisture status is possible via a variety of methods, including in situ monitoring, remote sensing, and numerical modeling. Although all of these approaches are rapidly evolving, there is no cohesive strategy or framework to integrateAuthorsMicheal Cosh, Todd Caldwell, Bruce M. Baker, John D. Bolton, Nathan Edwards, Peter Goble, Heather Hofman, Tyson Ochsner, Steven Quiring, Charles W. Schalk, Marina Skumanich, Mark Svoboda, Molly WoloszynSoil moisture product validation good practices protocol, version 1.0
The Global Climate Observing System (GCOS) included soil moisture in the list of Essential Climate Variables (ECVs) to express its important role in Earth’s water, energy and carbon cycle. Soil moisture has a major impact on agriculture, land surface hydrology, weather, and climate forecasting. This document is a community-based effort to provide recommendations on good practices for the validatioAuthorsCarsten Montzka, Michael H. Cosh, Bagher Bayat, Ahmad Al Bitar, Aaron Berg, Rajat Bindlish, Heye Reemt Bogena, John D. Bolton, Francois Cabot, Todd Caldwell, Steven Chan, Andreas Colliander, Wade Crow, Narendra Das, Gabrielle De Lannoy, Wouter Dorigo, Steven R. Evett, Alexander Gruber, Sebastian Hahn, Thomas Jagdhuber, Scott F. Jones, Yann Kerr, Seung-bum Kim, Christian Koyama, Mehmed Kurum, Ernesto Lopez-Baeza, Francesco Mattia, Kaighin A. McColl, Susanne Mecklenburg, Binayak Mohanty, Peggy O´Neill, Dani Or, Thierry Pellarin, George P. Petropoulos, Maria Piles, Rolf H. Reichle, Nemesio Rodriguez-Fernandez, Christoph Rüdiger, Tracy Scanlon, Robert C. Schwartz, Daniel Spengler, Prashant K. Srivastava, Swati Suman, Robin van der Schalie, Wolfgang Wagner, Urs Wegmüller, Jean-Pierre Wigneron, Fernando Camacho, Jaime NickesonUncertainty of reference pixel soil moisture averages sampled at SMAP core validation sites
Despite extensive efforts to maximize ground coverage and improve upscaling functions within core validation sites (CVS) of the NASA Soil Moisture Active/Passive (SMAP) mission, spatial averages of point-scale soil moisture observations often fail to accurately capture the true average of the reference pixels. Therefore, some level of pixel-scale sampling error from in situ observations must be coAuthorsFan Chen, W.T Crow, M.H. Cosh, A. Colliander, J. Asanuma, A. Berg, D.D. Bosch, Todd Caldwell, C. Holifield-Collins, J. Martínez-Fernández, H. McNairn, P.J. Starks, Z. Su, J.P. WalkerNon-USGS Publications**
Caldwell, T. G., B. D. Wolaver, T. Bongiovanni, J. P. Pierre, S. Robertson, C. Abolt, and B. R. Scanlon (2020), Spring discharge and thermal regime of a groundwater dependent ecosystem in an arid karst environment, Journal of Hydrology, 10.1016/j.jhydrol.2020.124947.Colliander, A., T. J. Jackson, A. Berg, D. D. Bosch, T. Caldwell, S. Chan, M. H. Cosh, C. H. Collins, J. Martínez-Fernández, H. McNairn, J. H. Prueger, P. J. Starks, J. P. Walker, and S. H. Yueh (2020), Effect of Rainfall Events on SMAP Radiometer-Based Soil Moisture Accuracy Using Core Validation Sites, Journal of Hydrometeorology, 21, 255-264, 10.1175/jhm-d-19-0122.1.Chaubell, M. J., J. Asanuma, A. A. Berg, D. D. Bosch, T. Caldwell, M. H. Cosh, C. H. Collins, J. Martinez-Fernandez, M. Seyfried, P. J. Starks, Z. Su, S. H. Yueh, M. Thibeault, J. Walker, R. S. Dunbar, A. Colliander, F. Chen, S. K. Chan, D. Entekhabi, R. Bindlish, and P. E. O'Neill (2020), Improved SMAP Dual-Channel Algorithm for the Retrieval of Soil Moisture, IEEE Transactions on Geoscience and Remote Sensing, 1-12, doi: 10.1109/tgrs.2019.2959239.Gholoubi, A., H. Emami, and T. Caldwell (2019), Deforestation effects on soil aggregate stability quantified by the high energy moisture characteristic method, Geoderma, 355, 113919, 10.1016/j.geoderma.2019.113919.Mayes, K. B., G. R. Wilde, M. E. McGarrity, B. Wolaver, and T. G. Caldwell (2019), Watershed-Scale Conservation of Native Fishes in the Brazos River Basin, Texas, in Multispecies and Watershed Approaches to Freshwater Fish Conservation, edited by D. C. Dauwalter, T. Birdson and G. P. Garret, pp. 315–343, American Fisheries Society Symposia 91, Bethesda, MD.Robertson, S., B. Wolaver, T. G. Caldwell, T. Birdson, R. Smith, T. Hardy, J. Lewey, and J. Joplin (2019), A multidisciplinary approach to developing the science and public support needed to maintain instream flows in the Devils River Basin, Texas, in Multispecies and Watershed Approaches to Freshwater Fish Conservation, edited by D. C. Dauwalter, T. Birdson and G. P. Garret, pp. 293–314, American Fisheries Society Symposia 91, Bethesda, MD.Das, N. N., D. Entekhabi, R. S. Dunbar, M. J. Chaubell, A. Colliander, S. Yueh, T. Jagdhuber, F. Chen, W. Crow, P. E. O'Neill, J. P. Walker, A. Berg, D. D. Bosch, T. Caldwell, M. H. Cosh, C. H. Collins, E. Lopez-Baeza, and M. Thibeault (2019), The SMAP and Copernicus Sentinel 1A/B microwave active-passive high resolution surface soil moisture product, Remote Sensing of Environment, 233, 111380, 10.1016/j.rse.2019.111380.Caldwell, T. G., T. Bongiovanni, M. H. Cosh, T. J. Jackson, A. Colliander, C. J. Abolt, R. Casteel, T. Larson, B. R. Scanlon, and M. H. Young (2019), The Texas Soil Observation Network: A comprehensive soil moisture dataset for remote sensing and land surface model validation, Vadose Zone Journal, 18:100034, doi:10.2136/vzj2019.04.0034.Sun, A. Y., Y. L. Xia, T. G. Caldwell, and Z. C. Hao (2018), Patterns of precipitation and soil moisture extremes in Texas, US: A complex network analysis, Advances in Water Resources, 112, 203-213, 10.1016/j.advwatres.2017.12.019.Kolassa, J., R. H. Reichle, Q. Liu, S. H. Alemohammad, P. Gentine, K. Aida, J. Asanuma, S. Bircher, T. Caldwell, A. Colliander, M. Cosh, C. Holifield Collins, T. J. Jackson, J. Martínez-Fernández, H. McNairn, A. Pacheco, M. Thibeault, and J. P. Walker (2018), Estimating surface soil moisture from SMAP observations using a Neural Network technique, Remote Sensing of Environment, 204, 43-59, doi: 10.1016/j.rse.2017.10.045.Das, N. N., D. Entekhabi, R. S. Dunbar, A. Colliander, F. Chen, W. Crow, T. J. Jackson, A. Berg, D. D. Bosch, T. Caldwell, M. H. Cosh, C. H. Collins, E. Lopez-Baeza, M. Moghaddam, T. Rowlandson, P. J. Starks, M. Thibeault, J. P. Walker, X. L. Wu, P. E. O'Neill, S. Yueh, and E. G. Njoku (2018), The SMAP mission combined active-passive soil moisture product at 9 km and 3 km spatial resolutions, Remote Sensing of Environment, 211, 204-217, doi:10.1016/j.rse.2018.04.011.Colliander, A., T. J. Jackson, S. K. Chan, P. O'Neill, R. Bindlish, M. H. Cosh, T. Caldwell, J. P. Walker, A. Berg, H. McNairn, M. Thibeault, J. Martinez-Fernandez, K. H. Jensen, J. Asanuma, M. S. Seyfried, D. D. Bosch, P. J. Starks, C. H. Collins, J. H. Prueger, Z. Su, E. Lopez-Baeza, and S. H. Yueh (2018), An assessment of the differences between spatial resolution and grid size for the SMAP enhanced soil moisture product over homogeneous sites, Remote Sensing of Environment, 207, 65-70, doi:10.1016/j.rse.2018.02.006.Chan, S. K., R. Bindlish, P. O'Neill, T. Jackson, E. Njoku, S. Dunbar, J. Chaubell, J. Piepmeier, S. Yueh, D. Entekhabi, A. Colliander, F. Chen, M. H. Cosh, T. Caldwell, J. Walker, A. Berg, H. McNairn, M. Thibeault, J. Martinez-Fernandez, F. Uldall, M. Seyfried, D. Bosch, P. Starks, C. H. Collins, J. Prueger, R. van der Velde, J. Asanuma, M. Palecki, E. E. Small, M. Zreda, J. Calvet, W. T. Crow, and Y. Kerr (2018), Development and assessment of the SMAP enhanced passive soil moisture product, Remote Sensing of Environment, 204, 931-941, doi: 10.1016/j.rse.2017.08.025.Caldwell, T. G., T. Bongiovanni, M. H. Cosh, C. Halley, and M. H. Young (2018), Field and laboratory evaluation of the CS655 soil water content sensor, Vadose Zone Journal, 17, 170214, doi:10.2136/vzj2017.12.0214.Bindlish, R., M. H. Cosh, T. J. Jackson, T. Koike, H. Fujii, S. K. Chan, J. Asanuma, A. Berg, D. D. Bosch, T. Caldwell, C. H. Collins, H. McNairn, J. Martinez-Fernandez, J. Prueger, T. Rowlandson, M. Seyfried, P. Starks, M. Thibeault, R. Van der Velde, J. P. Walker, and E. J. Coopersmith (2018), GCOM-W AMSR2 soil moisture product validation using core validation sites, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 11, 209-219, doi:10.1109/Jstars.2017.2754293.Abolt, C., T. Caldwell, B. Wolaver, and H. Pai (2018), Unmanned aerial vehicle-based monitoring of groundwater inputs to surface waters using an economical thermal infrared camera, Optical Engineering, 57, 9, 053113, doi:10.1117/1.Oe.57.5.053113.Young, M. H., J. H. Andrews, T. G. Caldwell, and K. Saylam (2017), Airborne LiDAR and Aerial Imagery to Assess Potential Burrow Locations for the Desert Tortoise (Gopherus agassizii), Remote Sensing, 9, ARTN 458, doi:10.3390/rs9050458.Reichle, R. H., G. J. M. De Lannoy, Q. Liu, J. V. Ardizzone, A. Colliander, A. Conaty, W. Crow, T. J. Jackson, L. A. Jones, J. S. Kimball, R. D. Koster, S. P. Mahanama, E. B. Smith, A. Berg, S. Bircher, D. Bosch, T. G. Caldwell, M. Cosh, A. Gonzalez-Zamora, C. D. H. Collins, K. H. Jensen, S. Livingston, E. Lopez-Baeza, J. Martinez-Fernandez, H. McNairn, M. Moghaddam, A. Pacheco, T. Pellarin, J. Prueger, T. Rowlandson, M. Seyfried, P. Starks, Z. B. Su, M. Thibeault, R. van der Velde, J. Walker, X. L. Wu, and Y. J. Zeng (2017), Assessment of the SMAP Level-4 Surface and Root-Zone Soil Moisture Product Using In Situ Measurements, Journal of Hydrometeorology, 18, 2621-2645, 10.1175/Jhm-D-17-0063.1.Ouellette, J. D., J. T. Johnson, A. Balenzano, F. Mattia, G. Satalino, S.-B. Kim, R. S. Dunbar, A. Colliander, M. H. Cosh, T. G. Caldwell, J. P. Walker, and A. A. Berg (2017), A time-series approach to estimating soil moisture from vegetated surfaces using L-band radar backscatter, IEEE Transactions on Geoscience and Remote Sensing, 55, 3186-3193, doi:10.1109/TGRS.2017.2663768.Kolassa, J., R. Reichle, Q. Liu, M. Cosh, D. Bosch, T. Caldwell, A. Colliander, C. Holifield Collins, T. Jackson, S. Livingston, M. Moghaddam, and P. Starks (2017), Data assimilation to extract soil moisture information from SMAP observations, Remote Sensing, 1179, doi:10.3390/rs9111179, 1179, doi:10.3390/rs9111179.Kim, S. B., J. J. van Zyl, J. T. Johnson, M. Moghaddam, L. Tsang, A. Colliander, R. S. Dunbar, T. J. Jackson, S. Jaruwatanadilok, R. West, A. Berg, T. Caldwell, M. H. Cosh, D. C. Goodrich, S. Livingston, E. Lopez-Baeza, T. Rowlandson, M. Thibeault, J. P. Walker, D. Entekhabi, E. G. Njoku, P. E. O'Neill, and S. H. Yueh (2017), Surface soil moisture retrieval using the L-band synthetic aperture radar onboard the Soil Moisture Active-Passive satellite and evaluation at core validation sites, IEEE Transactions on Geoscience and Remote Sensing, 55, 1897-1914, doi:10.1109/Tgrs.2016.2631126.Degre, A., M. J. van der Ploeg, T. Caldwell, and H. P. A. Gooren (2017), Comparison of Soil Water Potential Sensors: A Drying Experiment, Vadose Zone Journal, 16, 10.2136/vzj2016.08.0067.Colliander, A., T. J. Jackson, R. Bindlish, S. Chan, N. Das, S. B. Kim, M. H. Cosh, R. S. Dunbar, L. Dang, L. Pashaian, J. Asanuma, K. Aida, A. Berg, T. Rowlandson, D. Bosch, T. Caldwell, K. Caylor, D. Goodrich, H. al Jassar, E. Lopez-Baeza, J. Martinez-Fernandez, A. Gonzalez-Zamora, S. Livingston, H. McNairn, A. Pacheco, M. Moghaddam, C. Montzka, C. Notarnicola, G. Niedrist, T. Pellarin, J. Prueger, J. Pulliainen, K. Rautiainen, J. Ramos, M. Seyfried, P. Starks, Z. Su, Y. Zeng, R. van der Velde, M. Thibeault, W. Dorigo, M. Vreugdenhil, J. P. Walker, X. Wu, A. Monerris, P. E. O'Neill, D. Entekhabi, E. G. Njoku, and S. Yueh (2017), Validation of SMAP surface soil moisture products with core validation sites, Remote Sensing of Environment, 191, 215-231, doi:10.1016/j.rse.2017.01.021.Clewley, D., J. B. Whitcomb, R. Akbar, A. R. Silva, A. Berg, J. R. Adams, T. Caldwell, D. Entekhabi, and M. Moghaddam (2017), A method for upscaling in situ soil moisture measurements to satellite footprint scale using random forests, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 10, 2663-2673.Abolt, C. J., M. H. Young, and T. G. Caldwell (2017), Numerical Modelling of Ice-Wedge Polygon Geomorphic Transition, Permafrost and Periglacial Processes, 28, 347-355.Shellito, P. J., E. E. Small, A. Colliander, R. Bindlish, M. H. Cosh, A. A. Berg, D. D. Bosch, T. G. Caldwell, D. C. Goodrich, H. McNairn, J. H. Prueger, P. J. Starks, R. van der Velde, and J. P. Walker (2016), SMAP soil moisture drying more rapid than observed in situ following rainfall events, Geophysical Research Letters, 43, 8068-8075, 10.1002/2016gl069946.Chan, S. K., R. Bindlish, P. E. O'Neill, E. Njoku, T. Jackson, A. Colliander, F. Chen, M. Burgin, S. Dunbar, J. Piepmeier, S. Yueh, D. Entekhabi, M. H. Cosh, T. Caldwell, J. Walker, X. L. Wu, A. Berg, T. Rowlandson, A. Pacheco, H. McNairn, M. Thibeault, J. Martinez-Fernandez, A. Gonzalez-Zamora, M. Seyfried, D. Bosch, P. Starks, D. Goodrich, J. Prueger, M. Palecki, E. E. Small, M. Zreda, J. C. Calvet, W. T. Crow, and Y. Kerr (2016), Assessment of the SMAP passive soil moisture product, IEEE Transactions on Geoscience and Remote Sensing, 54, 4994-5007.Zhu, J. T., D. M. Sun, M. H. Young, T. G. Caldwell, and F. Pan (2015), Shrub spatial organization and partitioning of evaporation and transpiration in arid environments, Ecohydrology, 8, 1218-1228.Rau, B. M., J. C. Chambers, D. A. Pyke, B. A. Roundy, E. W. Schupp, P. Doescher, and T. G. Caldwell (2014), Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems, Rangeland Ecology & Management, 67, 506-521.Caldwell, T. G., T. Wohling, M. H. Young, D. P. Boyle, and E. V. McDonald (2013), Characterizing Disturbed Desert Soils Using Multiobjective Parameter Optimization, Vadose Zone Journal, 12, 1-23.Wilcox, B. P., L. Turnbull, M. H. Young, C. J. Williams, S. Ravi, M. S. Seyfried, D. R. Bowling, R. L. Scott, M. J. Germino, T. G. Caldwell, and J. Wainwright (2012), Invasion of shrublands by exotic grasses: ecohydrological consequences in cold versus warm deserts, Ecohydrology, 5, 160-173, 10.1002/eco.247.Flerchinger, G. N., T. G. Caldwell, J. Cho, and S. P. Hardegree (2012), Simultaneous Heat and Water (Shaw) Model: Model Use, Calibration, and Validation, Transactions of the ASABE, 55, 1395-1411.Caldwell, T. G., M. H. Young, E. V. McDonald, and J. T. Zhu (2012), Soil heterogeneity in Mojave Desert shrublands: Biotic and abiotic processes, Water Resources Research, 48, W09551, doi: 10.1029/2012wr011963.Rau, B. M., D. W. Johnson, R. R. Blank, R. J. Tausch, B. A. Roundy, R. F. Miller, T. G. Caldwell, and A. Lucchesi (2011), Woodland expansion’s influence on belowground carbon and nitrogen in the Great Basin U.S, Journal of Arid Environments, 75, 827-835.Rau, B. M., D. W. Johnson, R. R. Blank, A. Lucchesi, T. G. Caldwell, and E. W. Schupp (2011), Transition From Sagebrush Steppe to Annual Grass (Bromus tectorum): Influence on Belowground Carbon and Nitrogen, Rangeland Ecology & Management, 64, 139-147.Bacon, S. N., E. V. McDonald, T. G. Caldwell, and G. K. Dalldorf (2010), Timing and distribution of alluvial fan sedimentation in response to strengthening of late Holocene ENSO variability in the Sonoran Desert, southwestern Arizona, USA, Quaternary Research, 73, 425-438.Young, M. H., T. G. Caldwell, D. G. Meadows, and L. F. Fenstermaker (2009), Variability of soil physical and hydraulic properties at the Mojave Global Change Facility, Nevada: Implications for water budget and evapotranspiration, Journal of Arid Environments, 73, 733-744.Caldwell, T. G., E. V. McDonald, and M. H. Young (2009), The seedbed microclimate and active revegetation of disturbed lands in the Mojave Desert, Journal of Arid Environments, 73, 563-573.Caldwell, T. G., D. W. Johnson, W. W. Miller, R. G. Qualls, and R. R. Blank (2009), Prescription Fire and Anion Retention in Tahoe Forest Soils, Soil Science, 174, 594-600.McDonald, E. V., and T. G. Caldwell (2008), Geochemical characteristics of Iraqi dust and soil samples and related impacts to weapon malfunctions, in Military Geography and Geology: History and Technology, edited by C. P. Nathanail, R. J. Abrahart and R. P. Bradshaw, pp. 258-265, Land Quality Press, Nottingham.Caldwell, T. G., M. H. Young, J. T. Zhu, and E. V. McDonald (2008), Spatial structure of hydraulic properties from canopy to interspace in the Mojave Desert, Geophysical Research Letters, 35, L19406, doi:10.1029/2008gl035095.Caldwell, T. G., E. V. McDonald, S. N. Bacon, and G. Stullenbarger (2008), The performance and sustainability of vehicle dust courses for military testing, Journal Of Terramechanics, 45, 213-221.Bacon, S. N., E. V. McDonald, S. E. Baker, T. G. Caldwell, and G. Stullenbarger (2008), Desert terrain characterization of landforms and surface materials within vehicle test courses at US Army Yuma Proving Ground, USA, Journal Of Terramechanics, 45, 167-183.Shafer, D. S., M. H. Young, S. F. Zitzer, T. G. Caldwell, and E. V. McDonald (2007), Impacts of interrelated biotic and abiotic processes during the past 125 000 years of landscape evolution in the Northern Mojave Desert, Nevada, USA, Journal of Arid Environments, 69, 633-657.Caldwell, T. G., E. V. McDonald, and M. H. Young (2006), Soil disturbance and hydrologic response at the National Training Center, Ft. Irwin, California, Journal of Arid Environments, 67, 456-472.Young, M. H., E. V. McDonald, T. G. Caldwell, S. G. Benner, and D. G. Meadows (2005), Hydraulic properties of a desert soil chronosequence in the Mojave desert, USA, Vadose Zone Journal, 3, 956-963.Johnson, D. W., J. F. Murphy, R. B. Susfalk, T. G. Caldwell, W. W. Miller, R. F. Walker, and R. F. Powers (2005), The effects of wildfire, salvage logging, and post-fire N-fixation on the nutrient budgets of a Sierran forest, Forest Ecology And Management, 220, 155-165.Sisson, J. B., G. W. Gee, J. M. Hubbell, W. L. Bratton, J. C. Ritter, A. L. Ward, and T. G. Caldwell (2002), Advances in Tensiometry for Long-Term Monitoring of Soil Water Pressures, Vadose Zone Journal, 1, 310-315.Gee, G. W., A. L. Ward, T. G. Caldwell, and J. C. Ritter (2002), A vadose zone water fluxmeter with divergence control, Water Resources Research, 38, ARTN 1141, doi:10.1029/2001wr000816.Caldwell, T. G., D. W. Johnson, W. W. Miller, and R. G. Qualls (2002), Forest floor carbon and nitrogen losses due to prescription fire, Soil Science Society of America Journal, 66, 262-267.Johnson, D. W., R. B. Susfalk, R. A. Dahlgren, T. G. Caldwell, and W. W. Miller (2001), Nutrient fluxes in a snow-dominated, semi-arid forest: Spatial and temporal patterns, Biogeochemistry, 55, 219-245.**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.