Data Requirements for Groundwater Modelling

National Institute of HydrologyNational Institute of HydrologyRoorkee Roorkee –– 247667 (India)247667 (India)

C. P. KumarScientist ‘F’

All Lecture Notes and Powerpoint Presentations can be accessed at http://www.angelfire.com/nh/cpkumar/publication/

Google Search: Publications of C. P. Kumar

Presentation OutlinePresentation Outline

Groundwater in Hydrologic Cycle

Why Groundwater Modelling is needed?

Data Requirements for Groundwater Modelling

Boundary Conditions

Groundwater Modelling Software

Difference between MODFLOW and MIKE SHE

Online Discussion Groups

Groundwater in Hydrologic Cycle

Types of Terrestrial WaterTypes of Terrestrial Water

Ground waterGround water

SoilSoilMoistureMoisture

SurfaceWater

Unsaturated Zone / Zone of Aeration / Vadose (Soil Water)

Pores Full of Combination of Air and Water

Zone of Saturation (Ground water)

Pores Full Completely with Water

Groundwater

Important source of clean waterMore abundant than Surface Water

Linked to SW systems

Sustains flows in streams

Baseflow

Pollution

Groundwater Concerns

Groundwater miningSubsidence

Problems with groundwater

Ø Groundwater overdraft / mining / subsidence

Ø Waterlogging

Ø Seawater intrusion

Ø Groundwater pollution

Why Groundwater Modelling is needed?

Groundwater

• An important component of water resource systems.

• Extracted from aquifers through pumping wells and supplied for domestic use, industry and agriculture.

• With increased withdrawal of groundwater, the quality of groundwater has been continuously deteriorating.

• Water can be injected into aquifers for storage and/or quality control purposes.

Management of a groundwater system, means making such decisions as:

• The total volume that may be withdrawn annually from the aquifer.

• The location of pumping and artificial recharge wells, and their rates.

• Decisions related to groundwater quality.

Groundwater contamination by:

Ø Hazardous industrial wastes

Ø Leachate from landfills

Ø Agricultural activities such as the use of fertilizers and pesticides

v MANAGEMENT means making decisions to achieve goals without violating specified constraints.

v Good management requires information on the response of the managed system to the proposed activities.

v This information enables the decision-maker, to compare alternative actions and to ensure that constraints are not violated.

v Any planning of mitigation or control measures, once contamination has been detected in the saturated or unsaturated zones, requires the prediction of the path and the fate of the contaminants, in response to the planned activities.

v Any monitoring or observation network must be based on the anticipated behavior of the system.

v A tool is needed that will provide this information.

v The tool for understanding the system and its behavior and for predicting this response is the model.

v Usually, the model takes the form of a set of mathematical equations, involving one or more partial differential equations. We refer to such model as a mathematical model.

v The preferred method of solution of the mathematical model of a given problem is the analytical solution.

v The advantage of the analytical solution is that the same solution can be applied to various numerical values of model coefficients and parameters.

v Unfortunately, for most practical problems, because of the heterogeneity of the considered domain, the irregular shape of its boundaries, and the non-analytic form of the various functions, solving the mathematical models analytically is not possible.

v Instead, we transform the mathematical model into a numerical one, solving it by means of computer programs.

ALL GROUNDWATER HYDROLOGY WORK IS MODELING

A Model is a representation of a system.

Modeling begins when one formulates a concept of ahydrologic system, continues with application of, forexample, Darcy's Law or the Theis equation to theproblem, and may culminate in a complex numericalsimulation.

What is a Model?

• A model is anything that represents an approximation of a field situation

• Models include:– Mathematical models

• Numerical• Analytical

– Physical models• Sand tank

• A model is a simplified version of a real system and the phenomena that take place within it

TYPES OF MODELSCONCEPTUAL MODEL: QUALITATIVE DESCRIPTION OF SYSTEM "a cartoon of the system in your mind"

MATHEMATICAL MODEL: MATHEMATICAL DESCRIPTION OF SYSTEM

SIMPLE - ANALYTICAL (provides a continuous solution over the model domain)

COMPLEX - NUMERICAL (provides a discrete solution - i.e. values are calculated at only a few points)

ANALOG MODEL e.g. ELECTRICAL CURRENT FLOW through a circuit board with resistors to represent hydraulic conductivity and capacitors to represent storage coefficient

PHYSICAL MODEL e.g. SAND TANK which poses scaling problems

NOT THIS MODEL

THIS MODEL

Although groundwater flow models can't be as detailed or as complex as the real system, models are useful in at least four ways:

• Models integrate and assure consistency among aquifer properties, recharge, discharge, and groundwater levels.

• Models can be used to estimate flows and aquifer characteristics for which direct measurements are not available.

• Models can be used to simulate response of the aquifer under hypothetical conditions.

• Models can identify sensitive areas where additional hydrologic information could improve understanding.

Groundwater models are used to predict the effects of hydrologicalchanges on the behavior of the aquifer and are often namedgroundwater simulation models. Groundwater models are nowadaysused in various water management plans.

The mathematical or the numerical models are usually based on thereal physics of the groundwater flow. These mathematical equationsare solved using numerical codes such as MODFLOW, FEFLOW etc.

Governing Equations

• Flow Model

• Transport Model

RthS

zhhK

zyhhK

yxhhK

x zyx -¶¶

=÷øö

çèæ

¶¶

¶¶

+÷÷ø

öççè

涶

¶¶

+÷øö

çèæ

¶¶

¶¶

( ) Mcn

ccnq

tcRcv

xxcD

x e

bs

e

sdi

iiij

i

+÷÷ø

öççè

æ++-

¶¶

=¶¶

-÷÷ø

öççè

涶

¶¶ 'r

l

Dispersion Advection Sorption Source/Sink

First OrderDecay

MatrixDiffusion

Fluid continuity Storage Sources/sinks

Groundwater Flow Modelling: An Example

Predicting heads (and flows) in a confined aquifer

Solutions to the flow equationsMost groundwater flow models are solutions of some form of the ground water flow equation

x

xx

ho

x0

h(x)

x

Kq

“e.g., unidirectional, steady-state flow within a confined aquifer

The partial differential equation needs to be solved to calculate head as a function of position and time, i.e., h=f(x,y,z,t)

h(x,y,z,t)?

Darcy’s Law Integrated

Processes we might want to model

• Groundwater flow

- calculate both heads and flow

• Solute transport – requires information on flow (velocities)

- calculate concentrations

Numerical Solution of Equations

Numerically -- H or C is approximated at each point of a computational domain (may be a regular grid or irregular)

– May require intensive computational effort to get the desired resolution

– Subject to numerical difficulties such as convergence problems and numerical dispersion

– Generally, flow and transport are solved in separate independent steps (except in density-dependent or multi-phase flow situations)

Model Grids

Finite Element GridFinite Difference Grid

(K.J. Halford, 1991)

Calibration,Validation, and Sensitivity Analysis

– Calibration is the process of making the model match real-world data. Involves making several model runs, varying parameters until the ‘best fit’ is achieved.

– Validation is the process of confirming the validity of your calibration by using the model to fit an independent set of data.

– Sensitivity Analysis is the process of changing parameters to see the effects on the model results. The most sensitive parameters need to be checked for accuracy to ensure the best model.

Modeling ProtocolDefine Purpose

Write or Choose Code

Collect Field Data Conceptual Model

Mathematical Model

Numerical or Analytical

Verify Code

Model Design

Calibration

Prediction/Sensitivity Analysis

Verification

Presentation of Results

Postaudit

No

YesField Data

YesNo

Collect Field Data

Data Requirements for

Groundwater Modelling

Ø The success of any groundwater study, to a large measure, depends upon the availability and accuracy of measured/recorded data required for that study.

Ø Therefore, identifying the data needs and collection/monitoring of required data form an integral part of any groundwater exercise.

Ø The first phase of any groundwater study consists of collecting all existing geological and hydrological data on the groundwater basin in question.

Ø Any groundwater balance or numerical model requires a set of quantitative hydrogeological data that fall into two categories:

* Data that define the physical framework of the groundwater basin* Data that describe its hydrological framework

Defining Data Requirements

Ø General Data Needs

Ø Physical Framework and Hydrological Framework

Ø Hydrological Data Inputs and Operational Data Inputs

Ø Input Data for Flow Models and Transport Models

Model Output for Flow Models and Transport Models

One, Two or Three – Dimensional Models

General Data Needs• Topographic• Surface Water Elevations• Geologic• Hydrogeologic

– Conductivities– Groundwater Total Heads

• Climate– Rainfall– Evapotranspiration– Recharge

• Pumping Information• Irrigation information• Steady State or

Transient • Contaminates• Water Chemistry• Density Flow

– Salinity – NAPL

Physical Framework

1. Topography 2. Geology 3. Types of aquifers 4. Aquifer thickness and lateral extent5. Aquifer boundaries6. Lithological variations within the aquifer7. Aquifer characteristics

Hydrological Framework

1. Water table elevation2. Type and extent of recharge areas3. Rate of recharge4. Type and extent of discharge areas5. Rate of discharge

The data required for a groundwater flow modelling study under physical framework are:

§ Geologic map and cross section or fence diagram showing the areal and vertical extent and boundaries of the system.§ Topographic map at a suitable scale showing all surface water bodies and divides. Details of surface drainage system, springs, wetlands and swamps should also be available on map.§ Land use maps showing agricultural areas.§ Contour maps showing the elevation of the base of the aquifers and confining beds.§ Isopach maps showing the thickness of aquifers and confining beds.

These data are used for defining the geometry of the groundwater domain under investigation, including the thickness and areal extent of each hydrostratigraphic unit.

Under the hydrogeologic framework, the data requirements for a groundwater flow modelling study are:

§Water table and potentiometric maps for all aquifers.§ Hydrographs of groundwater head and surface water levels.§ Maps and cross-sections showing the hydraulic conductivity and/or transmissivity distribution.§ Maps and cross-sections showing the storage properties of the aquifers and confining beds.§ Spatial and temporal distribution of rates of evaporation, groundwater recharge, groundwater pumping etc.

Data inputs needed for the model:

• Hydrological data inputs• Operational data inputs• Initial and Boundary conditions• Hydraulic parameters

Hydrological Data Inputs

• Rainfall • Surface water infiltration• Evaporation• Evapotranspiration

These inputs may vary in both time and space. Some of this data is measured by climatological services (weather stations).

Operational Data Inputs - Water Management Data:

• Irrigation • Drainage • Pumping from wells • Water table information• Retention or infiltration basins

These inputs vary in quantity and quality.

Boundary Conditions (in detail later)

• Levels of the water table • Piezometric heads• Hydraulic head along the boundaries of the model (the head conditions)• Groundwater inflows and outflows along the boundaries of the model (the flow conditions).

Initial Conditions

The initial conditions refer to initial values of elements that may increase or decrease in the course of the time inside the model domain.

Hydraulic Parameters

• Geometry and distances in the domain to be modelled (geology, size of model)• Topography • Horizontal/vertical hydraulic conductivity of rock layers • Aquifer transmissivity • Aquifer porosity and storage coefficient• Capillarity of the unsaturated zone

Model Input Data (Flow)• Flow model input data

requirements– Defining hydrostratigraphic

units– Fluid sources (e.g. recharge,

interbasin flow)– Fluid Sinks (e.g. ET, pumping)– Boundary conditions (e.g.

specified flow, specified head, head-dependent)

– Model grid geometry– Time stepping information– Hydraulic Parameters– Initial hydraulic head

distribution

Model Output Data (Flow)

• Flow model output

– Hydraulic head values over space and time– Groundwater fluxes over space and time

Model Input Data (Transport)

• Transport model input requirements

– Fluid velocities– Initial distribution of contaminants– Sources and sinks for contaminants– Boundary conditions– Dispersion coefficients– Effective porosity– Decay and/or reaction coefficients– Contaminant loading functions

Model Output Data (Transport)• Transport model

output

– Contaminant concentrations over space and time

– Contaminant breakthrough curves at specified locations

Dimensions

Groundwater models can be one-dimensional, two-dimensional, and three-dimensional.

One-dimensional models can be used for the vertical flow in a system of parallel horizontal layers.

Two-dimensional models apply to a vertical plane while it is assumed that the groundwater conditions repeat themselves in other parallel vertical planes.

Three-dimensional models like MODFLOW require discretization of the entire flow domain. To that end, the flow region must be subdivided into smaller elements (or cells), in both horizontal and vertical sense. Within each cell, the parameters are maintained constant, but they may vary between the cells.

All these model inputs require a lot of data.

Data can be very manpower-intensive (READ EXPENSIVE!)

Do we spend the time and money now to get better management of our water resources?

OR

Do we wait until we are compelled to do so?

Boundary Conditions

Types of Boundary ConditionsTypes of Boundary Conditions1) Specified Head: head is defined as a function of space and time

(ABC, EFG) Constant Head: a special case of specified head (ABC, EFG)

2) Specified Flow: could be recharge across (CD) or zero across (HI) No Flow (Streamline): a special case of specified flow where the flow is zero (HI)

3) Head Dependent Flow: (ABC, EFG)

Free Surface: water-table, phreatic surface (CD) Seepage Face: h = z; pressure = atmospheric at the ground surface (DE)

Three basic types of Boundary ConditionsThree basic types of Boundary Conditions

(n is directional coordinate normal to the boundary)

Definition of Boundary and Initial Conditions in the Analysis of Saturated Gournd-Water Flow Systems - An Introduction, O. Lehn Franke, Thomas E. Reilly, and Gordon D. Bennett, USGS - TWRI Chapter B5, Book 3, 1987.

DIRICHLETDIRICHLETConstant Head & Constant Head & Specified Head Boundaries Specified Head Boundaries

Specified Head: Head (H) is defined as a function of time and space.

Constant Head: Head (H) is constant at a given location.

Implications: Supply Inexhaustible

NEUMANNNEUMANNNo Flow and No Flow and Specified Flow BoundariesSpecified Flow Boundaries

Specified Flow: Discharge (Q) varies with space and time.

No Flow: Discharge (Q) equals 0 across boundary.

Implications: H will be calculated as the value required to produce a gradient to yield that flow, given a specified hydraulic conductivity (K). The resulting head may be above the ground surface in an unconfined aquifer, or below the base of the aquifer where there is a pumping well; neither of these cases are desirable.

CAUCHYCAUCHYHead Dependent FlowHead Dependent Flow

Head Dependent Flow: H1 = Specified head in reservoir H2 = Head calculated in model

Implications:•If H2 is below AB, q is a constant and AB is the seepage face, but model may continue to calculate increased flow. •If H2 rises, H1 doesn't change in the model, but it may in the field. •If H2 is less than H1, and H1 rises in the physical setting, then inflow is underestimated. •If H2 is greater than H1, and H1 rises in the physical setting, then inflow is overestimated.

Free SurfaceFree Surface

Free Surface: h = Z, or H = f(Z)

e.g. the water table h = z

or a salt water interface

Note, the position of the boundary is not fixed!Implications: Flow field geometry varies so transmissivity will vary with head (i.e., this is a nonlinear condition). If the water table is at the ground surface or higher, water should flow out of the model, as a spring or river, but the model design may not allow that to occur.

Seepage SurfaceSeepage SurfaceSeepage Surface: The saturated zone intersects the ground surface at atmospheric pressure and water discharges as evaporation or as a downhill film of flow.

The location of the surface is fixed, but its length varies (unknown a priori).

Implications: A seepage surface is neither a head or flowline. Often seepage faces can be neglected in large scale models.

Natural and Artificial BoundariesNatural and Artificial BoundariesIt is most desirable to terminate your model at natural geohydrologic boundaries. However, we often need to limit the extent of the model in order to maintain the desired level of detail and still have the model execute in a reasonable amount of time.

Consequently models sometimes have artificial boundaries.

For example, heads may be fixed at known water table elevations at a country line, or a flowline or ground-water divide may be set as a no-flow boundary.

Natural and Artificial BoundariesNatural and Artificial BoundariesBOUNDARY TYPE NATURAL

EXAMPLES ARTIFICIAL USES

CONSTANT Fully Penetrating Surface Water Features

Distant Boundary (Line of unchanging hydraulic head contour) or

SPECIFIED HEAD SPECIFIED FLOW Precipitation/Recharge Flowline

Pumping/Injection Wells Divide Impermeable material Subsurface Inflow

HEAD DEPENDENT FLOW

Rivers Distant Boundary (Line of unchanging hydraulic head contour)

Springs (drains) EvapotranspirationLeakage From a Reservoir or Adjacent Aquifer

Hydrologic Features as BoundariesHydrologic Features as Boundaries

• Boundary can be assigned to hydrologic feature such as:– Surface water body

• Lake, river, or swamp– Water table

• Recharge and evapotranspiration or source/sink specified head

– Impermeable surface• Bedrock or permeable unit pinches out

Groundwater / SurfaceGroundwater / Surface--water Interactionwater Interaction

• Hydraulic head in aquifer can be equal to elevation of surface-water feature or allowed to leak to the surface-water feature.

• Usually defined as a “Constant-Head” or “Specified Head” Boundary or “Head-dependent flow” boundary.

• If elevation of SW changes, as with streams, elevation of the boundary condition changes.

How a stream How a stream could interact with could interact with the groundwater the groundwater

systemsystem

T.E. Reilly, 2000

NoNo--Flow BoundaryFlow Boundary

• Hydraulic conductivity contrasts between units– Alluvium on top of tight bedrock

• Assume groundwater does not move across this boundary

• Can use ground-water divide or flow line

NoteNote: groundwater divide shifts after : groundwater divide shifts after developmentdevelopment——may not be a good nomay not be a good no--flow BCflow BC

T.E. Reilly, 2000

Water Table or “Flow” BoundaryWater Table or “Flow” Boundary• Intermittent areal recharge on water-table

– Moves through unsaturated zone– Volume of water per unit area per unit of time entering

the groundwater system is specified– May vary with time and space

• Evapotranspiration occurs when plants remove water from the water-table– May be head-dependent (if water-table too far below

land surface, ET is unlikely)– Volume of water per unit area per unit of time leaving

the GW system as a function of depth to water is specified

– May vary in space and time

Wells Wells -- an internal boundary an internal boundary condition at a point condition at a point -- thought of as thought of as

a stress to the systema stress to the system

• A well is a specified flow rate at a point– Can be pumping or injecting water– Withdrawals or injection may vary in space

and time

Practical ConsiderationsPractical Considerations

• Boundary conditions must be assigned to every point on the boundary surface.

• Modeled boundary conditions are usually greatly simplified compared to actual conditions.

Groundwater Modelling Software

Name of Software Type of Software Description

MODFLOW Simulation of saturated flow Open source software developed by the USGS, based on a block-centred finite difference algorithm. Relies on a large number of modular packages that add specific capabilities. Most packages are also open source and can therefore be modified by end users. Can be coupled to MT3DMS and other codes to simulate solute transport, as well as MIKE 11 for flow in river and stream networks.

FEFLOW Simulation of saturated and unsaturated flow, transport of mass (multiple solutes) and heat, with integrated GUI

Commercial software based on the finite element method. Several versions with different capabilities. Extendable using plug-ins that can be developed by end users to expand the capabilities, during or after computations. Can be coupled to MIKE 11 to simulate flow in river and stream networks.

SUTRA Simulation of saturated and unsaturated flow, transport of mass and heat

Open source software based on the finite element method, designed for density-coupled flow and transport.

MT3DMS Simulation of transport of multiple reactive solutes in groundwater

Open source software that can be coupled with MODFLOW to compute coupled flow and transport.

SEAWAT Simulation of saturated flow and transport of multiple solutes and heat

Open source software combining MODFLOW and MT3DMS for density-coupled flow and transport.

MIKE SHE Integrated catchment modelling, with integrated GUI

Commercial software that uses the finite difference method for saturated groundwater flow, several representations of unsaturated flow, including the 1D Richards equation, MIKE 11 for flow in river and stream networks and the 2D diffusive-wave approach for overland flow.

Visual MODFLOW GUI Commercial software. Supports MODFLOW (with many packages), MODPATH, SEAWAT, MT3DMS, MT3D99, RT3D, PHT3D, MGO, , MODFLOW-SURFACT, MIKE 11.

Groundwater Vistas GUI Commercial software. Supports MODFLOW (with many packages), MODPATH, SEAWAT, MT3DMS, , MODFLOW-SURFACT.

GMS GUI Commercial software. Supports MODFLOW (with many packages), MODPATH, MODAEM, SEAWAT, MT3DMS, RT3D, SEAM2D, , SEEP2D, FEMWATER.

PMWIN GUI Commercial software. Supports MODFLOW (with many packages), MODPATH, SEAWAT, MT3DMS, PHT3D, .

ArcGIS GIS Commercial software to manage spatial data. Capabilities can be extended using ArcPy, an implementation of the Python scripting language.

Surfer Gridding and contouring Commercial software to manage and plot spatial data.

Hydro GeoAnalyst Management of hydrogeologicaldata

Visualisation of bore logs, fence diagrams. Creation of hydrostratigraphic layers. Incorporates elements of ArcGIS.

RockWorks Management of hydrogeological data

Visualisation of bore logs, fence diagrams. Creation of hydrostratigraphic layers. Can be linked to ArcGIS.

ArcHydro Groundwater Management of hydrogeological data

Visualisation of bore logs, fence diagrams. Creation of hydrostratigraphic layers. Tightly linked with ArcGIS.

PEST Parameter estimation and uncertainty analysis

Open-source software designed to allow parameter estimation for any model. Available in many implementations to support specific groundwater models and GUIs.

Difference between MODFLOW and MIKE SHE

Ø MIKE SHE considers all the individual components of hydrologic cycle through five basic modules (overland flow, channel flow, evapotranspiration, unsaturated flow and saturated groundwater flow). By incorporating unsaturated zone and overland flow appropriately, it calculates infiltration, actual evapotranspiration and recharge from their physical laws.

Ø MODFLOW is restricted to simulate groundwater flow in the saturated zone.

Ø MODFLOW includes recharge as an upper boundary condition to the groundwater model. It is usually done by applying a constant or varying fraction to the measured precipitation data. Since the model results are very sensitive to this fraction, recharge to groundwater is taken as calibration parameter.

Ø MIKE SHE includes snowmelt but MODFLOW does not incorporate.

Ø (As compared to MIKE SHE), MODFLOW requires lesser data for model development, lesser operating time, relatively easy to learn through the user’s manual, rectangular grid size allowed, finer model grid for a specific area of interest.

Differences between MODFLOW and MIKE SHE

MODFLOW MIKE SHE

“Essentially, all models are wrong, but some are useful“

- George Edward Pelham Box (1919-2013)

Online Discussion Groups

This list aims to provide a forum for discussion of scientific research in all aspects of Hydrology including hydrologic design, surface water analysis and modelling, flood studies, drought studies, watershed development, groundwater assessment and modelling, conjunctive use, drainage, mountain hydrology, environmental hydrology, lake hydrology, nuclear hydrology, urban hydrology, forest hydrology, hydrological investigations, remote sensing and GIS applications etc. Exchange of ideas and experiences regarding use and application of hydrological softwares are also welcome.

Members : 1985Founded : Jan 15, 2002

https://groups.yahoo.com/neo/groups/hydforum/info

Post Message : hydforum@yahoogroups.comSubscribe : hydforum-subscribe@yahoogroups.comUnsubscribe : hydforum-unsubscribe@yahoogroups.comList Owner : hydforum-owner@yahoogroups.com

•Members :1985•Founded :Jan 15, 2002•Founded :Jan 15, 2002

Hydrology Forum

This mailing list aims to provide a forum for discussion of scientific research in modelling of hydrologic systems including * Rainfall-Runoff Modelling * Overland Flow Modelling * Unsaturated Flow Modelling * Groundwater Flow Modelling * Solute Transport Modelling * Sea Water Intrusion Modelling * Water Quality Modelling * Other relevant aspects of Hydrology and Water Resources Development and Management. It intends to provide a forum for technical discussions; announcement of new public domain and commercial softwares; calls for abstracts and papers; conference and workshop announcements; and summaries of research results, recent publications, and case studies. Exchange of ideas and experiences regarding use and application of hydrological softwares are also welcome.

Members : 1079Founded : Oct 28, 2003

https://in.groups.yahoo.com/neo/groups/hydrologymodel/info

Post Message : hydrologymodel@yahoogroups.co.inSubscribe : hydrologymodel-subscribe@yahoogroups.co.inUnsubscribe : hydrologymodel-unsubscribe@yahoogroups.co.inList Owner : hydrologymodel-owner@yahoogroups.co.in

•Members :1985•Founded :Jan 15, 2002•Founded :Jan 15, 2002

Hydrological Modelling

The "Ground Water Modelling" group is a forum for the communication of all aspects of ground water modelling including technical discussions; announcement of new public domain and commercial softwares; calls for abstracts and papers; conference and workshop announcements; and summaries of research results, recent publications, and case studies.

Members : 1774Founded : Sep 12, 2001

https://groups.yahoo.com/neo/groups/gwmodel/info

Post Message : gwmodel@yahoogroups.comSubscribe : gwmodel-subscribe@yahoogroups.comUnsubscribe : gwmodel-unsubscribe@yahoogroups.comList Owner : gwmodel-owner@yahoogroups.com

•Members :1985•Founded :Jan 15, 2002•Founded :Jan 15, 2002

Ground Water Modelling

A forum for exchange of ideas and experiences regarding use and application of MODFLOW - a modular three-dimensional finite-difference ground-water flow model.

Members : 624Founded : Dec 8, 2004

http://groups.google.com/group/modflow/

Group email: modflow@googlegroups.com Owner email: modflow-owner@googlegroups.com

Subscribe online at the group page.

•Members :1985•Founded :Jan 15, 2002•Founded :Jan 15, 2002

MODFLOW Users Group

MODFLOW Users Group

Thank You !!!