Center for Research in Water Resources
This module describes different methods for representing and modeling terrain, the subsurface, and water flow in a GIS. Some common environmental representation techniques include tracking elevation changes, modeling surface water runoff, modeling groundwater flow, and developing subsurface diagrams. These representations provide important information about the characteristics of a site or a region. For instance, if a chemical is spilled and leaches to groundwater, knowing how far and fast this chemical moves is vital to making decisions about which areas could be affected by the release. Many of these models can be developed completely within ArcView using the Spatial Analyst or Watershed Delineator extension. Other interfaces are available which connect a GIS with an external program. Researchers at Brigham Young University have created interfaces which link ArcView and Arc/Info with other programs such as MODFLOW and HEC-1. CRWR-PrePro is a University of Texas product that calculates flow direction, flow accumulation, and watersheds using a Digital Elevation Model (DEM).
The Engineering Computer Graphics Laboratory at Brigham Young University has created a Groundwater Modeling System (GMS) and a Watershed Modeling System (WMS). These systems are comprehensive graphical user environments that perform groundwater and surface water simulations. GMS consists of a graphical user interface (the GMS program) and a number of analysis codes (MODFLOW, MT3D, MODPATH, SEEP2D, and FEMWATER). The program setup allows for coverages to be shared between GMS and Arc/Info. The focus of WMS is to provide a single application which integrates digital terrain models with industry standard runoff models such as HEC-1 and TR-20. Similar to GMS, the necessary files for use with WMS can be generated using ArcView and Arc/Info.
EQuIS Geology:EQuIS Geology is a subsurface data management application that allows a user to store and analyze geologic and hydrogeologic data. EQuIS Geology can be connected with ArcView to display soil borings, fenceline diagrams, and solid models. It can also linked with GMS to develop groundwater models.
Spatial Data:One of the new and exciting capabilities of ArcView is visualizing surfaces in three dimensions. The recently released 3-D Analyst extension for ArcView allows users to view and analyze Triangulated Irregular Networks (TIN). A TIN is simply a set of points that are connected to form triangles. Each point has an x and y coordinate along with a z coordinate that refers to a unique attribute of the coverage, such as an elevation or concentration measurement. TINs are useful because they provide better surface representations than DEMs. In a DEM, each grid cell is the same size and has only one elevation value, but in a TIN, each triangle encompass a range of elevations. The figure below shows a TIN for part of an oil refinery. A creek runs through the left side of the image, and there is a lagoon in the center.
Using the 3-D Analyst extension, a TIN can be created from a grid or DEM. A TIN can also be created from a point coverage of survey measurements, which is a useful tool for many engineering design applications. 3-D Analyst adds a 3-D scene viewer to the project window. This scene viewer can be used to display TINs, rotate a TIN, and circle around an area of interest. It can also be used to overlay two-dimensional coverages, such as physical features or photographs. For instance, a building coverage could be added to the figure above, and an elevation for each of these buildings could be assigned so that the buildings are three-dimensional.
CRWR-PrePro -- a system of ArcView scripts and associated controls -- has been developed to extract hydrologic, topographic and topologic information from digital spatial data of a hydrologic system, and to prepare an input file for the Hydrologic Modeling System (HMS) developed by the Hydrologic Engineering Center (HEC) of the United States Army Corps of Engineers. Starting with the DEM and a SCS curve number grid, CRWR-PrePro delineates streams and watersheds, calculates parameters for each of them, determines their interconnectivity, and prepares an input file for HMS that includes the computed hydrologic parameters.
The first attempt to connect GIS data layers with HEC's HMS was developed by F. Hellweger and D. Maidment. This first version of CRWR-PrePro takes stream and subbasin coverages and analyzes them to produce a schematic model which defines and spatially connects seven types of hydrologic elements in the landscape: subbasins, reaches, junctions, diversions, reservoirs, sources, sinks. Graphics depicting some Exciting Success Stories illustrate the application of CRWR-PrePro to basins of the City of Austin, of Texas, of the Upper Mississippi and Missouri Rivers, and of the Niger River in West Africa.
Further development of CRWR-PrePro led to a more complete system that -- besides the capabilities of the first version -- delineates streams and watersheds in addition to calculating the hydrologic parameters of each of them. At present, CRWR-PrePro is able to calculate the required hydrologic parameters for calculating abstractions according to the Soil Conservation Service curve number method, watershed routing according to the Soil Conservation Service dimensionless unit hydrograph, and stream routing with the Muskingum and lag methods.
To run CRWR-PrePro, the following files have to be retrieved from the directory GISEnv98/EnvRep/hecfiles:
Additional information on CRWR-PrePro can be found at:
Developed by Andrew Romanek at the Center for Research in Water Resources at The University of Texas at Austin, the following avenue scripts are for use with ArcView 3.1. Many of these scripts will require revision to suit the needs of individual projects. For an extensive collection of scripts, visit ESRI's Scripts page.
Julie Kim
Center for Research in Water Resources
The University of Texas at Austin
Austin, TX 78712
E-mail: juki@mail.utexas.edu
