Prepared in cooperation with the Bureau of Reclamation Groundwater Discharge by Evapotranspiration, Dixie Valley, West-Central Nevada, March 2009–September 2011 Professional Paper 1805 Version 1.1, April 2015 U.S. Department of the Interior U.S. Geological Survey Cover: Upper left: Eddy-covariance evapotranspiration station at the sparse vegetation site (site 394348118040205). Photograph taken by Amanda Garcia, U.S. Geological Survey, June 3, 2009. Upper right : Transect measurement tape located near the northwestern playa edge. Photograph taken by Wesley Henson, U.S. Geological Survey, June 17, 2010. Lower left: Sunrise chamber evaporation measurements at the sparse vegetation evapotranspiration site (site 394348118040205). Photograph taken by Jena Huntington, U.S. Geological Survey, April 11, 2010 Lower right: Soil coring on the playa for water content and stable isotope analyses (site 394559118013705). Photograph taken by Amanda Garcia, U.S. Geological Survey, July 8, 2010. Groundwater Discharge by Evapotranspiration, Dixie Valley, West-Central Nevada, March 2009–September 2011 By C. Amanda Garcia, Jena M. Huntington, Susan G. Buto, Michael T. Moreo, J. LaRue Smith, and Brian J. Andraski Prepared in cooperation with the Bureau of Reclamation Professional Paper 1805 Version 1.1, April 2015 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Acting Director U.S. Geological Survey, Reston, Virginia First release: 2014 Revised: April 2015 (ver. 1.1) For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Garcia, C.A., Huntington, J.M., Buto, S.G., Moreo, M.T., Smith, J.L., and Andraski, B.J., 2015, Groundwater discharge by evapotranspiration, Dixie Valley, west-central Nevada, March 2009–September 2011 (ver. 1.1, April 2015): U.S. Geological Survey Professional Paper 1805, 90 p., http://dx.doi.org/10.3133/pp1805. ISSN 2330-7102 (online) iii Contents Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................2 Purpose and Scope ..............................................................................................................................4 Description of Study Area ............................................................................................................................4 General Hydrology ................................................................................................................................4 Water Use ..............................................................................................................................................7 Vegetation ..............................................................................................................................................7 Groundwater Discharge by Evapotranspiration—Site Scale ................................................................8 Surface Energy Budget ........................................................................................................................8 Eddy-Covariance Method, Data Collection, and Monitoring .........................................................9 Site Selection and Description ..................................................................................................9 Dense Vegetation Site ......................................................................................................11 Sparse Vegetation Site ....................................................................................................11 Playa 1 Site ........................................................................................................................11 Playa 2 Site ........................................................................................................................14 Instrumentation and Site Maintenance .................................................................................14 Data Correction, Filtering, and Gap-Filling Procedures .....................................................15 Net Radiation .....................................................................................................................16 Volumetric Water Content ...............................................................................................17 Turbulent Fluxes ................................................................................................................17 Precipitation ......................................................................................................................19 Source Area of Measurements ...............................................................................................20 Energy-Balance Closure ...........................................................................................................21 Vegetation, Soil Physics, and Groundwater Monitoring .....................................................23 Evapotranspiration .............................................................................................................................24 Environmental Variables Affecting Evapotranspiration ......................................................24 Precipitation and Air Temperature .................................................................................24 Vegetation and Surface Characteristics .......................................................................26 Near-Surface Soil-Water Content and Electrical Conductivity ................................27 Soil Physics ........................................................................................................................28 Water Content and Water Storage Trends ..........................................................28 Soil Temperature and Hydraulic Head Trends ....................................................30 Liquid-Water Fluxes .................................................................................................34 Water-Level Fluctuations.................................................................................................36 Energy-Balance Closure and Trends ......................................................................................38 Eddy-Covariance Evapotranspiration and Trends ................................................................41 Groundwater Discharge by Evapotranspiration ..................................................................45 Uncertainty..................................................................................................................................46 Available Energy ...............................................................................................................46 Turbulent Fluxes and Evapotranspiration ....................................................................46 Precipitation .....................................................................................................................48 iv Contents—Continued Groundwater Discharge by Evapotranspiration—Site Scale—Continued Water Sourcing ..................................................................................................................................48 Chamber Evaporation ................................................................................................................48 Stable Isotopes ..........................................................................................................................50 Groundwater Evapotranspiration Partitioning .....................................................................51 Chamber Evaporation and Evapotranspiration Partitioning ......................................51 Source Water ....................................................................................................................54 Groundwater Discharge by Evapotranspiration—Basin Scale ...........................................................59 Groundwater Discharge Area ..........................................................................................................59 Evapotranspiration Units ..................................................................................................................59 Satellite Image Processing .....................................................................................................61 Atmospheric Correction ..................................................................................................62 Calculation and Evaluation of Vegetation Indexes ......................................................62 Brightness