1. Arc Hydro groundwater data model
ESRI User Conference
July 2005
I will be presenting my dissertation proposal, which is design a groundwater data model and extending ArcHydro to include groundwater features.
We have been working on this project for over a year …
In the presentation I will try to introduce some basic concepts of data modeling and why it is done a
And the concepts of arc hydro, why we want to extend it, and why I think this is important.
Gil Strassberg, David R. Maidment, and Norman L. Jones

2. Arc Hydro surface water
A data model for representing surface water systems
Here is the core Arc Hydro data model for surface water.
The hydrological system is described through a set of components that characterize the system.
These include:
Drainage systems – define the drainage areas – catchments, watersheds and basins
Hydrography – describe features such as streams, lakes and monitoring points
Hydro network – a geometric network that creates connectivity between features.
Channels – a detailed description of channels, cross sections and profile lines.
On top of the geographical representation arc hydro also includes temporal data in the format of time series. There is a structure to define a variety of time series and the relationships between the temporal data and the geographical features.
The idea here is that this format is useful for a variety of studies and models, and it is easy to access this information and apply tools because it is in a standard format.
As you can see the existing framework only deals with surface water, and it has become apparent that groundwater features should be added to better represent reality.
Published by ESRI press, 2002

3. Goals of the data model Objective Data model goals
Develop a data model for representation of groundwater systems.
Data model goals
Support representation of regional and site scale groundwater systems.
Enable the integration of surface water and groundwater data.
Connection to groundwater modeling software.

4. Regional groundwater systems
Regional groundwater systems can be defined as a volume of the subsurface through which ground water flows, from recharge areas to discharge areas
Examples of regional studies are water availability programs and susceptibility assessments.
Usually the horizontal scale is much larger than the vertical scale
These systems are modeled many times as two dimensional flow models, where the subsurface is described as a one layer system and vertical flow is negligible compared to horizontal flow.
Vertical scale about 3000 ft.
Usually the horizontal scale >> vertical scale
In many cases modeled as 2 dimensional flow system

5. Site scale groundwater studies
Characterization of Savannah River Site in South Carolina
Site scale groundwater studies are required at many construction projects, landfills, burial grounds, and generally whenever an evaluation of contaminated sites is needed
We are not trying to represent a complete groundwater system, rather the purpose is to describe in detail a small section of interest within a larger system
The goal is usually to model water and contaminant movement within the site, and this requires the construction of a 3D model of the subsurface.
Vertical dimension ~ Top 250 bottom ~ 50 overall about 200 ft.
Usually model 3D flow to study mass transport
Important to establish a 3D model of the system

6. Integration of surface water and groundwater information
Need to represent movement of water between the surface and subsurface
Geographic relationship between the surface and groundwater elements
In may studies and management programs surface water systems and groundwater systems are described and managed separately.
But we want to be able to integrate these components of the hydrologic cycle better understand issues such as water availability, contaminant transport etc.
This is a complex subject, and I am not sure how we are going to address this issue.
But a good starting point is to use the geographic relationships between the surface and groundwater elements.
For example, to estimate recharge from streams we need to know where the streams are, do the flow across an outcrop.
Then we can start asking questions about how the stream and the outcrop interact, gaining stream? Loosing stream? etc.. But the geographic relationship is a good starting point.
Conjunctive view and analysis of information from groundwater and surface water systems

7. Connection to groundwater models
Data model = Database
Model input
Model outputs
Numerical modeling of groundwater is an important aspect of the hydrogeologic discipline , we use numerical models to study water availability, water flow, and mass transport within groundwater systems.
One benefit of constructing data models is the integration of model inputs and results. A conceptual representation of the groundwater system allows a variety of models to interface with the information and the results can also be written back into the central database.
This allows for much easier and constructed integration of models, where one models input can be the output of another model.
Even if we just use the database to construct model inputs, at least we know all models have the same basic geographic description.

8. Data model framework
Features describing the hydrogeology of the system
Table that describes hydrogeologic units and their properties
Features used in relation with modeling
Raster catalog to represent geologic formations and parameter distribution
Raster catalog to represent water related parameters
Describes surfaces

9. Hydrogeology feature dataset
Wells (points)
Aquifer (2D Polygon)
GeoArea (2D Polygon)
GeoLine (2D line)
GeoVolume (Multipatch)
GeoSection (3D polygon)
BoreLine (3D line)

10. Hydrogeologic unit
Describes the hydrogeologic unit and links together the spatial representations
Hydrogeologic unit table
HGU ID
HGU Code
Formation
Reference 1
Sand 2 8
Red Clay 3 23
Bouldery till

11. Hydraulic conductivity
GeoRasters
Raster catalog
GeoRasters:
Distribution of properties
Define boundaries of hydrogeologic units
Transmisivity
Hydraulic conductivity
Raster ID
Description
Units 1
Transmisivity
m2/day 2
Hydraulic
conductivity
m/day 3
Formation top m 4
Formation base
Top of formation
Formation base
GeoRasters are usually constant over time
Woodbine aquifer, Texas

12. Potentiometric surface
Rasters Series
describe water related properties over time
Potentiometric
surface
Saturated
thickness
Raster ID
Description
Units
Time 1
Potentiometric surface m
May 2003 2
June 2003 3
July 2003
Contaminant
concentration

13. Modeling feature dataset
Connection to modeling tools: enable the preparation of model inputs and communication of model outputs
2 dimensional models
3 dimensional models

14. Tools
Develop tools that help create and populate the data model classes
Many of the objects are three dimensional and require custom tools to populate the classes
Tools to connect with models

15. Example 1: Representing hydrogeology of an aquifer system
North Carolina coastal aquifer system

16. North Carolina coastal aquifer system
Section line
I want to walk through a short example to try and illustrate some of these concepts.
The Neuse River Bain in North Carolina. We chose this site because it is the test basin for CHUASI and for implementing the hydrologic information system.
It is about 300 km in length and in it’s widest part about 80 km in width.
Underlying the river basin there is a coastal aquifer system.
Another reason for selecting this area is the availability of information, there is an abundance of information describing the subsurface in the area, and much of it is accessible.
* From USGS, Water Resources Data Report of North Carolina for WY 2002

17. Example 2: Representation of 3D site scale measurements
Case study of the MADE (Macrodispersion Experiment) site

18. MADE site Text files: tracer concentrations
Hydraulic conductivity measurements
Hydraulic head measurements
From Harvey and Gorelick.
WATER RESOURCES RESEARCH, VOL. 36, NO. 3, PAGES 637–650, MARCH 2000

19. 3D sampling ports
A well can be related to multiple sampling ports

20. Querying and displaying 3D measurements
Creates a new temporary layer with measurements for a specific variable, in a certain value range, at a selected time

21. Interpolation using new 3D tools
Tetrahedral network of Bromide concentrations
3D interpolation tools
Isosurfaces of Bromide concentrations

22. Example 3: Interfacing with MODFLOW
Barton Spring segment of the Edwards aquifer GAM model

23. GAM models for the Edwards Aquifer
MODFLOW models are developed as part of the GAM models for Texas
Models can be downloaded from the TWDB website

24. Model Boundary
Using external models we can create solid models that can then be stored and visualized within GIS
Given this information, we want to interpolate the observation data to generate new representations of the subsurface. We want to create cross sections and fence diagrams and to be able to create solid models of the subsurface.
These examples show how fence diagrams and solids can be generated by connecting observations.
We generate these objects to help us describe and reason about the structure of the subsurface.

25. Model dimensions The model is 1 layer with 120 by 120 cells
Barton Creek
Williamson Creek
Slaughter Creek
Bear Creek
Onion Creek
Interstream recharge
No recharge
The model is 1 layer with 120 by 120 cells
Each cell is 1000 by 500
Steady state (20 years) and transient (10 years) models
Model Packages: Recharge, Well, Drain

26. Tools to populate the relevant classes in the data model from MODFLOW files

27. Aggregate and query the model results from GIS
Define zones of interest through GIS
Get Budgets for the defined zones

28. Future work Finalize the conceptual data model design
Create a detailed database design
Get feedback from the groundwater community Refine the model and test on more case studies

29. For more information and updates
Websites:
ESRI Data models website:
Gil Strassberg website:
GIS Water Resources Consortium, CRWR UT Austin:
Contacts:
Gil Strassberg –
David R. Maidment –
Norman L. Jones