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

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

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.

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. http://www.edwardsaquifer.net/geology.html#present Usually the horizontal scale >> vertical scale In many cases modeled as 2 dimensional flow system

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

For more information and updates Websites: ESRI Data models website: www.support.esri.com/datamodels Gil Strassberg website: https://webspace.utexas.edu/gstras/MyWebsite/ GIS Water Resources Consortium, CRWR UT Austin: http://www.crwr.utexas.edu/giswr/ Contacts: Gil Strassberg – gilstras@mail.utexas.edu David R. Maidment – Maidment@mail.utexas.edu Norman L. Jones njones@byu.edu