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User's Guide to the Variably Saturated Flow

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User's Guide to the Variably Saturated Flow User’s Guide to the Variably Saturated Flow (VSF) Process for MODFLOW 1.00 0.90 0.80 0.70 0.60 0.50 0.40 Soil saturation, dimensionless Soil saturation, z Constant-headcell x Techniques and Methods 6–A18 U.S. Department of the Interior U.S. Geological Survey User’s Guide to the Variably Saturated Flow (VSF) Process for MODFLOW By R. Brad Thoms, Richard L. Johnson, and Richard W. Healy Techniques and Methods 6–A18 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior Dirk Kempthorne, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: April 2006 Revised and reprinted: November 2006 For sale by U.S. Geological Survey, Information Services Box 25286, Denver Federal Center Denver, CO 80225 For more information about the USGS and its products: Telephone: 1-888-ASK-USGS World Wide Web: http://www.usgs.gov/ Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Thoms, R.B., Johnson, R.L., and Healy, R.W., 2006, User’s guide to the Variably Saturated Flow (VSF) Process for MOD- FLOW: U.S. Geological Survey Techniques and Methods 6–A18, 58 p. Prepared by the U.S. Geological Survey in Lawrence, Kansas (http://ks.water.usgs.gov) iii Preface A new Variably Saturated Flow (VSF) Process was written for use with the U.S. Geological Survey (USGS) MODFLOW–2000 ground-water model. The VSF Process is designed to simulate three- dimensional flow through variably saturated soil media within the vadose zone. The performance of this computer program has been tested in models of hypothetical ground-water flow systems; however, future applications of the programs may reveal errors that were not detected in the test simulations. Users are requested to notify the authors if errors are found in the documentation report or in the computer program. Correspondence regarding the report or program should be sent to: Center for Groundwater Research OGI School of Science & Engineering Oregon Health & Science University 20000 NW Walker Road Beaverton, Oregon 97006–8921 USA Attention: R. Brad Thoms or Richard L. Johnson Although the computer program has been written and used by the USGS, no warranty, expressed or implied, is made by the USGS or the United States Government as to the accuracy and function- ality of the program and related program material. Nor shall the fact of distribution constitute any such warranty, and no responsibility is assumed by the USGS in connection therewith. MODFLOW–2000, the VSF Process, and other ground-water programs are available from the USGS at the following World Wide Web (WWW) addresses: http://water.usgs.gov/software/ http://water.usgs.gov/nrp/gwsoftware/ or by anonymous ftp file transfer from directory /pub/software/ground_water/modflow at ftp address: water.usgs.gov iv v Contents Abstract. 1 Introduction . 1 Authors' Note . 2 Acknowledgments . 2 Overview, Compatibility, and Applicability. 3 Richards' Equation Flow Package . 4 Conceptualization. 4 Governing Equation for Variably Saturated Flow . 5 Soil Characteristic Functions. 6 Program Description . 9 Input Instructions . 10 Output Data . 11 Seepage Face Package . 12 Conceptualization. 12 Program Description . 12 Input Instructions . 13 Output Data . 13 Surface Ponding Package. 14 Conceptualization. 14 Program Description . 14 Input Instructions . 15 Output Data . 16 Surface Evaporation Package. 16 Conceptualization. 16 Program Description . 17 Input Instructions . 18 Output Data . 19 Root Zone Evapotranspiration Package. 19 Conceptualization. 19 Program Description . 20 Input Instructions . 21 Output Data . 23 Adaptive Time-Stepping Package . 23 Conceptualization. 23 Program Description . 23 Input Instructions . 25 Output Data . ..
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