IGW-NET · Users' Reference Manual

Learn IGW-NET by workflow, then use it as a reference.

A searchable, chapter-based guide for building, running, interpreting, calibrating, and extending groundwater models in MAGNET4WATER.

Start with first model Browse all chapters
New userBuild your first modelFastest route to a working simulation. PractitionerCalibrate to field dataObserved heads, multipliers, and model checking. Advanced modelerRegional-to-local nestingCarry boundary conditions into refined submodels. TroubleshootingCommon pitfallsSymptoms, causes, fixes, and cross references.
Getting Started Core Workflow Advanced Modeling Reference Resources

Part I · Getting Started

3 chapters
Chapter 01 · Part I · Getting Started What IGW-NET Is and When to Use It The platform's philosophy, capabilities, and limits. What IGW-NET does well, what other tools do better, and how to decide if it's the right fit for your problem. Chapter 02 · Part I · Getting Started Account Setup and Platform Navigation Creating a MAGNET4WATER account, logging in, understanding the main menus, and orienting yourself in the modeling environment. Chapter 03 · Part I · Getting Started Your First Model — A Guided Walkthrough Ten minutes from "I just logged in" to "I have a working steady-state groundwater flow simulation on my screen." The fastest path to confidence.

Part II · Core Workflow

5 chapters
Chapter 04 · Part II · Core Workflow Step 1 — Defining the Model Domain Drawing rectangles, drawing polygons, importing from text files, importing from shapefiles. How to choose the right domain size; what "nested model" means and when it matters; how the domain's shape affects everything downstream. Chapter 05 · Part II · Core Workflow Step 2 — Assigning Aquifer Attributes The conceptual heart of IGW-NET. Top and bottom elevation, hydraulic conductivity, porosity, storage, recharge, and surface drainage — what each parameter means, how to choose good values, when to use Data Center rasters versus your own data, and the four most common mistakes. Chapter 06 · Part II · Core Workflow Step 3 — Adding Features (Zones, Lines, Wells) The three types of conceptual features and when to reach for each. How zones are not just polygons, how lines are not just lines, and what the Zone Attributes menu's five tabs actually do. Chapter 07 · Part II · Core Workflow Step 4 — Running the Simulation What happens when you click SIMULATE. Projection prompts explained. Monitoring convergence. Reading error messages. What to do when the solver fails — and why it usually isn't what you think. Chapter 08 · Part II · Core Workflow Step 5 — Interpreting the Results Head contours, velocity vectors, cross-sections, water balance, 3D surface plots. Reading what the model is telling you, and recognizing when it's telling you something suspicious.

Part III · Advanced Modeling

12 chapters
Chapter 09 · Part III · Advanced Modeling Transient Simulation — Modeling Time Moving from steady-state to time-dependent flow. Time steps, stress periods, initial conditions, and time-varying inputs. When transient is worth the complexity and when it isn't. Chapter 10 · Part III · Advanced Modeling Vertical Layering — When 2D Is Not Enough Computational sublayers vs. conceptual geologic layers — the distinction that trips up almost everyone. When to use each, how many you need, and what happens when you get it wrong. Chapter 11 · Part III · Advanced Modeling Particle Tracking — The Everyday Transport Tool The first-line transport analysis for most practical questions. Forward tracking for impact zones, backward tracking for capture zones and wellhead protection areas. Zone, line, rectangle, polygon, and well-based particle placement. Advection-plus-random-walk for visualizing dispersion. No additional calibration parameters — particles use the flow field you already have. Chapter 12 · Part III · Advanced Modeling Contaminant Transport — Plume Concentration Modeling When particle tracking isn't enough. Every source pathway (internal and external) and the "water flowing IN" rule. The five physical processes — advection, dispersion, diffusion, sorption, decay. Multi-species and chain reactions (BTEX, PCE/TCE). Dual-domain transport for fractured media. SEAWAT for variable-density problems. 2D vs 3D and the water-table-as-top workflow. Chapter 13 · Part III · Advanced Modeling Nested Modeling — Regional Context, Local Detail The natural application of the xyz-to-ijk framing from Ch. 1. Draw a rectangular zone, check Submodel Domain and Boundary Condition from Parent Model, simulate — the child gets regional flow as BCs while resolving local features at finer grid. Supports hierarchies (submodels inside submodels) for multi-scale problems. Also covers MODFLOW-6 unstructured refined grid as the feature-specific alternative. Chapter 14 · Part III · Advanced Modeling Surface Water as Boundary Conditions for Groundwater How GW models handle SW as a boundary condition — the three levels of representation (DEM-as-drain, explicit head-dependent lines, coupled modeling), the physics of head-dependent flux, where stage comes from (DEM as water-surface snapshot), stream-order hierarchy, hydrography datasets (NHD, HydroSHEDS), the climate gradient (Michigan ~5–10% losing reaches vs Arizona where SW is often a source to GW), and the central pitfall: DEM-based stages on small streams can produce head-dependent flux into the aquifer 10× larger than rainfall. Why small streams must be one-way drains. Naturally leads to Ch. 15 on coupled lake-aquifer modeling. Chapter 15 · Part III · Advanced Modeling Coupled Lake-Aquifer Modeling — When Stage Becomes a Solution When SW-as-BC is no longer enough. Explicit lake-aquifer coupling with stage as a solution variable, not an input. Lakes with significant storage, wetland systems, and the Barron Lake integrated case study. Beyond head-dependent flux: when SW and GW together are the system. Chapter 16 · Part III · Advanced Modeling The Watershed Solver — Overland Flow, Infiltration, and Runoff IGW-NET's in-platform watershed processes subsystem. When to enable it; the Overland Flow Options dialogs (Land Use, Climate, Soil Type); the Manning's n gotcha (stored everywhere, active only when the solver is on); seasonal rainfall patterns; infiltration-as-recharge coupling; runoff delivery to coupled lakes (Ch. 15); and the SwaNET two-platform architecture with UTM projection handshake. SwaNET sees the basin; IGW-NET sees the aquifer; surface truth meets subsurface truth. Chapter 17 · Part III · Advanced Modeling T-PROGS — 3D Geology from Boreholes Realistic heterogeneous 3D aquifer K fields from borehole data via transition probability geostatistics. The four-class typology (AQ, MAQ, PCM, CM) makes T-PROGS parametrically tractable — four scalar K values characterize a full 3D heterogeneous field. Regional zonation when geology varies (N zones × 4 = 4N parameters). The Barron Lake 4-material pattern as example. Automated water-well lithology coverage for approximately 10 US states, plus all Canadian provinces. Chapter 18 · Part III · Advanced Modeling Calibration — Reconciling the Model with Reality Static Water Levels from regional well databases as primary observations; filtering via the Well Data Processing Tool; K multiplier and Recharge multiplier with Calib checkboxes in Multiplying Factors; reading the calibration chart (observed vs. simulated scatter); the manual calibration loop; Automatic Calibration with UCODE parameter estimation; multi-target calibration for coupled models (Barron Lake: lake stages + well heads jointly); K-recharge non-uniqueness and why head-only calibration is dangerous; common pitfalls including overfitting, local minima, and trusting a perfect fit. Chapter 19 · Part III · Advanced Modeling Stochastic Modeling — Heterogeneity, Uncertainty, and Recursive Statistics Both single-realization simulation (what heterogeneity does to flow) and ensemble Monte Carlo (uncertainty quantification). Sequential Gaussian Simulation for continuous random fields alongside T-PROGS (Ch. 17) for categorical materials. IGW-NET's recursive ensemble-statistics architecture — running mean, variance, and probability distributions updated per realization using Welford's algorithm without storing the ensemble, making 2D/3D stochastic analysis computationally tractable at full resolution. Macrodispersion, probabilistic capture zones, parameter uncertainty from UCODE as stochastic input, and the critical limitation that stochastic analysis does not quantify structural uncertainty. Chapter 20 · Part III · Advanced Modeling MODFLOW Integration — IGW-NET and the Industry-Standard Engines The multi-engine architecture: native IGW solver + industry-standard USGS engines (MODFLOW 6, MODFLOW 2005, MODFLOW-USG, MODFLOW-NWT + MT3DMS + SEAWAT + UCODE) under the hood. Automatic engine selection (MF6 DISV for unstructured/refined grids from Ch. 13; native IGW for standard structured flow). Feature-to-package mapping (wells→WEL, DEM drain→DRN, streams→RIV, coupled lakes→LAK, etc.). What doesn't transfer (Watershed Solver, interactive tools). Export workflow for regulatory submission, external validation, and handoff to MODFLOW-ecosystem tools.

Part IV · Reference

5 chapters
Chapter 21 · Part IV · Reference Menu Reference — Every Button, Organized by Tier Dense reference catalog of IGW-NET's interface organized around the four-tier tool structure — Conceptual Model Tools (build), Simulation Tools (run), Analysis Tools (interpret), Other Tools (manage). Every toolbar button documented with purpose, the chapter where the underlying workflow is taught, and cross-reference to realtime help for operational details. Designed for lookup rather than sequential reading. Chapter 22 · Part IV · Reference Common Pitfalls & Gotchas Reference The consolidated troubleshooting reference. Unit and value traps, boundary-condition traps, grid and discretization traps, calibration and solver traps, workflow and integration traps. Each entry names the symptom, the cause, and the fix with a cross-reference to the chapter that covers the mechanism in depth. Bookmark this one. Chapter 23 · Part IV · Reference Data Center Reference — Spatial Data That Feeds IGW-NET Parser-backed catalog of Data Center datasets: DEM / elevation (USGS NED 1m/10m/30m, ASTER, SRTM); hydraulic conductivity (GLHYMPS 2.0, USGS Glacial K, Michigan state datasets, USA/Canada T); aquifer thickness (Rock Top MI, Global AQ Thickness, US & Canada compilations); recharge (Global w/MI Patch, USGS Long-term Mean, NASA IMERG, Europe/Africa); borehole lithology and SWLs covering approximately 10 US states, plus all Canadian provinces; streams and lakes auto-loaded from Global Database. Global Database vs DataNET distinction, and the metadata gap (dataset IDs are stored in model files; names are resolved via parser catalogs). Chapter 24 · Part IV · Reference Solver Options Reference — gmSolverID Position Map Parser-backed reference for solver configuration. The gmSolverID position map (positions 0-3 for flow solver / max iterations / tolerance / damping; colon-separated transport options; positions 17-20 for density flow / auto-calibration / Monte Carlo / MFsolverStr MODFLOW variant). Flow solver variants (Hybrid SOR default, PCG, SIP, SOR, MODFLOW 6 IMS). Convergence parameters and the triad (iterations → tolerance → damping). Transport solver choice (Magnet native vs MT3D). Convergence troubleshooting escalation ladder — when numerical adjustments don't work, the problem is structural. Chapter 25 · Part IV · Reference Error Messages & Diagnostics — Triage by Symptom Triage guide organized by symptom class rather than error code. The triage workflow (verify defaults first, identify symptom class, diagnose specifically). Convergence failures (max iterations, oscillation, NaN). Water table issues including the 10×-rainfall pitfall. Mass balance diagnostics. Wrong flow direction — prescribed BCs vs structural error hidden behind head-only calibration. No solution / empty output. Transport and particle-tracking issues. Extensive cross-references to Ch. 14 §14.7 (10×-rainfall), Ch. 18 §18.1.3 (structure-first), Ch. 20 (NWT for wetting/drying), Ch. 24 (solver ladder).

Part V · Resources

4 chapters
Chapter 26 · Part V · Resources Help Resources — A Map to the Documentation Ecosystem Map of the full IGW-NET documentation ecosystem. Three primary pillars (Users' Manual for concepts, Realtime Help with approximately 179 operational reference pages, Platform Reference for parser-backed field detail). Interactive learning resources (28 Quick Tutorials, Concept Pages, video tutorials). Real-world examples (Mancelona TCE, Barron Lake case studies). Ecosystem context (MAGNET4WATER Observatory spanning approximately 43 countries and approximately 143 cities, Global Model Network, five-platform architecture). Support channels (in-app feedback, community forums, direct support). Chapter 27 · Part V · Resources Learning Paths — Sequences Tailored to Your Role Curated learning sequences through the manual for different user types. Universal Starter Path (4-6 hours, for everyone). Then role-specific paths: academic (graduate student, teaching faculty with 14-week course sequence); professional (contamination consultant, water-supply planner, regulatory reviewer); research (stochastic methods and uncertainty); platform-switcher (MODFLOW/GMS users transitioning). Each path lists specific chapters in recommended order with concise rationale, tutorials to complete, case studies to read, and time estimates. Chapter 28 · Part V · Resources Glossary — Terminology for IGW-NET and Groundwater Modeling Alphabetical glossary with 133 entries covering both classical groundwater modeling terminology (head, K, advection, capture zone, dispersion) and IGW-NET-specific terms (Global Base Model, DataNET, MFsolverStr, four-tier tool organization, AQ/MAQ/PCM/CM, recursive statistics, compute-render-discard, 10×-rainfall pitfall). 100% coverage of key concepts from Parts I-IV. Each entry cross-referenced to the chapter where the term is explained in depth. Chapter 29 · Part V · Resources Collaborative Workflows — IGW-NET in the Ecosystem The closing chapter. The MAGNET4WATER Observatory as integrated information layer (approximately 43 countries, approximately 143 cities). Model Publishing workflow (three images + video animation + name + description). Global Model Network discovery and adaptation. Team workflow patterns (primary-reviewer, distributed, consulting, research) with nested-modeling as natural division of labor. DataNET for specialized data sharing with filename prefix detection. Cross-platform integration (IGW-NET with SwaNET, StormNET, ConduitNET). Closing reflection on the 13 foundational principles that span the manual and a final invitation to do good modeling work.