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MODFLOW-2000, The U.S. Geological Survey Modular Ground-Water Model - User Guide to Modularization Concepts and the Ground-Water Flow Process

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MODFLOW-2005 : the U.S. Geological Survey modular ground-water model--the ground-water flow process

Mathematical models have become indispensable tools for studying vadose zone flow and transport processes. We reviewed the history of development, the main processes involved, and selected applications of HYDRUS and related models and software packages developed collaboratively by several groups in the United States, the Czech Republic, Israel, Belgium, and the Netherlands. Our main focus was on modeling tools developed jointly by the U.S. Salinity Laboratory of the USDA, Agricultural Research Service, and the University of California, Riverside. This collaboration during the past three decades has resulted in the development of a large number of numerical [e.g., SWMS_2D, HYDRUS-1D, HYDRUS-2D, HYDRUS (2D/3D), and HP1] as well as analytical (e.g., CXTFIT and STANMOD) computer tools for analyzing water flow and solute transport processes in soils and groundwater. The research also produced additional programs and databases (e.g., RETC, Rosetta, and UNSODA) for quantifying unsaturated soil hydraulic properties. All of the modeling tools, with the exception of HYDRUS-2D and HYDRUS (2D/3D), are in the public domain and can be downloaded freely from several websites.

Development and Applications of the HYDRUS and STANMOD Software Packages and Related Codes

A number of changes have been made to the U.S. Geological Survey modular finite-difference ground-water flow model, which is commonly known as MODFLOW. Existing MODFLOW input files will work with the revised model. Also, the basic structure and computational methods of the model have been maintained. Those familiar with the original model should have no difficulty adapting to the revised model. Some of the most significant changes are: 1. All files are opened with Fortran OPEN statements. The user must prepare an additional file that specifies the model files to be opened. 2. The array-reading subroutines have been enhanced to make it easier to prepare the array control records. When using the new control record, all the parameters are read using free format; however, the original fixed-format control records can still be used if desired. 3. For input not read with array-reading subroutines, an option to use free format has been added. This avoids the need to place data values in specified columns of input records, and thus will prevent the common error of entering data in incorrect columns. If this option is not used, data are read using the original fixed format fields. 4. The capability to produce an output listing that is 80 columns wide (rather than 132) has been added in order to facilitate printing on 8.5-inch wide paper and viewing on a video display screen. All the miscellaneous output has been reduced to 80 columns, and several new formats that are 80 columns wide have been added to the array-printing subroutines. 5. A new method for specifying output control has been added. This new method uses words rather than numeric codes for specifying the various output options. New options have also been added such as the ability to save calculated heads in formatted files and save budget data in more compact unformatted files. The old method of specifying output control can still be used. 6. Budget calculations have been changed to double precision, which improves the accuracy of budget calculations. Inaccuracy of budget calculations was sometimes noticeable in the original model when a grid of 100,000 or more cells was used or when a large conductance was used in a head-dependent stress term. 1U.S. Geological Survey, Reston, VA 2McDonald Morrissey Associates, Reston, VA

/pdf/user-s-documentation-for-modflow-96-an-update-to-the-u-s-4j3m9ieefz.pdf

User's documentation for MODFLOW-96, an update to the U.S. Geological Survey modular finite-difference ground-water flow model

A major research plan entitled “Integrated research on the ecohydrological process of the Heihe River Basin” was launched by the National Natural Science Foundation of China in 2010. One of the key aims of this research plan is to establish a research platform that integrates observation, data management, and model simulation to foster twenty-first-century watershed science in China. Based on the diverse needs of interdisciplinary studies within this research plan, a program called the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) was implemented. The overall objective of HiWATER is to improve the observability of hydrological and ecological processes, to build a world-class watershed observing system, and to enhance the applicability of remote sensing in integrated ecohydrological studies and water resource management at the basin scale. This paper introduces the background, scientific objectives, and experimental design of HiWATER. The instrumental setting and airborne mission plans a...

Heihe Watershed Allied Telemetry Experimental Research (HiWATER): Scientific Objectives and Experimental Design

The history of MODFLOW.

The U.S. Geological Survey Modular Ground-Water Flow Model, commonly referred to as MODFLOW, simulates ground-water flow through porous media using the finite-difference method. The region being modeled is divided into a grid of cells, and each cell is defined to be either no-flow, variable-head, or constant-head. The model calculates a value for head at all variable-head cells whereas head at constant-head cells is specified by the user. Cells are designated as no-flow cells if they contain impermeable material or are unsaturated, and accordingly the flow of water is not simulated in such cells. As originally published, MODFLOW could simulate the desaturation of variable-head model cells, which resulted in their conversion to no-flow cells, but could not simulate the resaturation of cells. That is, a no-flow cell could not be converted to variable head. However, such conversion is desirable in many situations. For example, one might wish to simulate pumping that desaturates some cells followed by the recovery of water levels after pumping is stopped. An option that allows cells to convert from noflow to variable-head has been added to the model. In this option, a cell is converted to variable head based on the head at neighboring cells. The option is written in FORTRAN 77 and is fully compatible with the existing model. This report documents the new option, including a description of the concepts, detailed input instructions, and a listing of the code. Example problems illustrate the practical applications of the option. Although solution of the modified flow equations can be difficult for the model solvers, the example problems show that it is possible to solve a variety of complex problems.

/pdf/a-method-of-converting-no-flow-cells-to-variable-head-cells-1cyu3p0rux.pdf

Michael G. McDonald

Papers

MODFLOW-2000, The U.S. Geological Survey Modular Ground-Water Model - User Guide to Modularization Concepts and the Ground-Water Flow Process

The history of MODFLOW.

A method of converting no-flow cells to variable-head cells for the U. S. Geological Survey modular finite-difference ground-water flow model

Models of ground water systems--not just tools but components in a scientific approach.

DISCUSSION OF “Technical Note on MODFLOW Notation” by R. Stillwater, C. Kraeger‐Rovey, and P. Scott