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| Scientific Investigations Report 2006–5009 |

# MODOPTIM: A General Optimization Program for Ground-Water Flow Model Calibration and Ground-Water Management with MODFLOW

 By Keith J. Halford 

**Version 1.0**

##  Abstract

 MODOPTIM is a non-linear ground-water model calibration and management tool that simulates flow with MODFLOW-96 as a subroutine. A weighted sum-of-squares objective function defines optimal solutions for calibration and management problems. Water levels, discharges, water quality, subsidence, and pumping-lift costs are the five direct observation types that can be compared in MODOPTIM. Differences between direct observations of the same type can be compared to fit temporal changes and spatial gradients. Water levels in pumping wells, wellbore storage in the observation wells, and rotational translation of observation wells also can be compared. Negative and positive residuals can be weighted unequally so inequality constraints such as maximum chloride concentrations or minimum water levels can be incorporated in the objective function. Optimization parameters are defined with zones and parameter-weight matrices. Parameter change is estimated iteratively with a quasi-Newton algorithm and is constrained to a user-defined maximum parameter change per iteration. Parameters that are less sensitive than a user-defined threshold are not estimated. MODOPTIM facilitates testing more conceptual models by expediting calibration of each conceptual model. Examples of applying MODOPTIM to aquifer-test analysis, ground-water management, and parameter estimation problems are presented. 

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This report is contained in the following files:

| -  **Scientific Investigations Report 2006-5009.pdf** (1.2 MB) | **For viewing and printing upon download.***(This version of the report is accessible as defined in Section 508 of the Rehabilitation Act of 1973, Amendments of 1998.)* |
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| -  **MODOPTIM_all_v1.1.zip** (28.3 MB)                         | **All files - PDF, speadsheets, codes, and executables for download.**                                                                                                   |
| -  **Modoptim_v1.1_Code+EXE_ONLY.zip** (702 KB)                | **Code and executables.**                                                                                                                                                |

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##  Contents

Abstract

Introduction     Purpose and Scope

The Optimization Problem     Objective Function          Observation Types           Weights     Optimization Parameters           Zonation and Parameter-Weight Matrices          Parameter-Weight Matrices from Iso-Value Contours     Optimization Algorithm           Minimization Algorithms           Parameter Sensitivity and Ranking of Parameters Parameter Scaling     Implementation of Minimization Algorithm in MODOPTIM 

MODOPTIM—Organization and Structure     MODOPTIM and MODFLOW files     Coordinate Systems     Zonation     Parameter-Weight Matrices    Optimization Parameters     Observations        Interpolation of Point Observations        Special Cases for Water-Level Observations           Water-Levels in Pumping Wells           Wellbore Storage in Observation Wells          Rotation of Observation Wells        Subsidence Observations        Flow Observations        Optimization Constraints        Comparison of Observation Differences     Weighting of Observations          Inequality Comparisons          Different Observation Types     Output and Analysis of Results         Parameter Estimates and Optimization Results          Residuals and Sensitivities 
Comparison to Other Programs 

References 

Appendix A. Input structures used in MODOPTIM files 

Appendix B. Input for main optimization file 

Appendix C. Input for composite MODFLOW/MODOPTIM file with parameters to be estimated 

Appendix D. Input for grid discretization file 

Appendix E. Time-variant hydraulic-property package (VAR1) 

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 Send questions or comments about this report to the author, Keith Halford at khalford@usgs.gov, 775.887.7614.For more information about USGS activities in Nevada, visit the **Nevada       Water Science Center home page**.AccessibilityFOIAPrivacyPolicies and Notices
U.S. Department of the Interior, U.S. Geological SurveyPersistent URL: http://pubsdata.usgs.gov/pubs/sir/2006/5009/		Page Contact Information: USGS Publishing NetworkLast modified: Thursday, December 01 2016, 07:00:09 PM