Prepared in cooperation with the U.S. Geological Survey Water Availability and Use Science Program MODFLOW 6 – Description of Input and Output Version mf6.0.0—August 11, 2017 U.S. Department of the Interior U.S. Geological Survey Cover. Binary computer code illustration. Contents Introduction.......................................................................................1 Running a Simulation...............................................................................1 Form of Input Instructions...........................................................................2 Block and Keyword Input.......................................................................2 Specification of Block Information in OPEN/CLOSE File............................................3 File Name Input...............................................................................4 Lengths of Character Variables.................................................................4 Simulation Name File...............................................................................5 Structure of Blocks............................................................................5 Explanation of Variables........................................................................5 Example Input File.............................................................................7 Temporal Discretization (TDIS) Package..............................................................8 Structure of Blocks............................................................................8 Explanation of Variables........................................................................8 Example Input File.............................................................................9 Groundwater Flow (GWF) Model Input............................................................... 10 Information for Existing MODFLOW Users........................................................ 10 Array Input (READARRAY)...................................................................... 15 READARRAY Control Line.................................................................. 15 READARRAY Variable Descriptions.......................................................... 16 READARRAY Examples..................................................................... 17 List Input..................................................................................... 18 Units of Length and Time....................................................................... 19 Steady-State Simulations...................................................................... 20 Volumetric Budget............................................................................. 20 Cell-By-Cell Flows............................................................................. 21 GWF Model Name File......................................................................... 23 Structure of Blocks........................................................................ 23 Explanation of Variables................................................................... 23 Example Input File......................................................................... 24 Structured Discretization (DIS) Input File........................................................ 26 Structure of Blocks........................................................................ 26 Explanation of Variables................................................................... 26 Example Input File......................................................................... 27 Discretization with Vertices (DISV) Input File..................................................... 28 Structure of Blocks........................................................................ 28 Explanation of Variables................................................................... 29 Example Input File......................................................................... 30 i Unstructured Discretization (DISU) Input File..................................................... 32 Structure of Blocks........................................................................ 32 Explanation of Variables................................................................... 33 Example Input File......................................................................... 35 Initial Conditions (IC) Package.................................................................. 36 Structure of Blocks........................................................................ 36 Explanation of Variables................................................................... 36 Example Input File......................................................................... 36 Output Control (OC) Option..................................................................... 37 Structure of Blocks........................................................................ 37 Explanation of Variables................................................................... 37 Example Input File......................................................................... 38 Observation (OBS) Utility for a GWF Model....................................................... 39 Example Observation Input File............................................................. 39 Node Property Flow (NPF) Package............................................................. 40 Structure of Blocks........................................................................ 40 Explanation of Variables................................................................... 40 Example Input File......................................................................... 42 Horizontal Flow Barrier (HFB) Package.......................................................... 43 Structure of Blocks........................................................................ 43 Explanation of Variables................................................................... 43 Example Input File......................................................................... 44 Storage (STO) Package........................................................................ 45 Structure of Blocks........................................................................ 45 Explanation of Variables................................................................... 45 Example Input File......................................................................... 46 Constant-Head (CHD) Package................................................................. 47 Structure of Blocks........................................................................ 47 Explanation of Variables................................................................... 47 Example Input File......................................................................... 49 Available observation types................................................................ 49 Example Observation Input File............................................................. 49 Well (WEL) Package........................................................................... 51 Structure of Blocks........................................................................ 51 Explanation of Variables................................................................... 51 Example Input File......................................................................... 53 Available observation types................................................................ 54 Example Observation Input File............................................................. 54 Drain (DRN) Package.......................................................................... 55 Structure of Blocks........................................................................ 55 Explanation of Variables................................................................... 55 Example Input File......................................................................... 57 Available observation types................................................................ 57 ii Example Observation Input File............................................................. 57 River (RIV) Package........................................................................... 59 Structure of Blocks........................................................................ 59 Explanation of Variables................................................................... 59 Example Input File......................................................................... 61 Available observation types................................................................ 61 Example Observation Input File............................................................. 62 General-Head Boundary (GHB) Package......................................................... 63 Structure of Blocks........................................................................ 63 Explanation of Variables................................................................... 63 Example Input File......................................................................... 65 Available observation types................................................................ 65 Example Observation Input File............................................................. 66 Recharge (RCH) Package – List-Based Input..................................................... 67 Structure of Blocks........................................................................ 67 Explanation of Variables..................................................................