GISHydro97 - Introduction

David R. Maidment

Center for Research in Water Resources, University of Texas at Austin

Hi! Welcome to GISHydro97, a collection of exercises, data, reports and information designed to support the use of Geographic Information Systems in Hydrology and Water Resources. These materials are mostly drawn from the work of a community of graduate students, research scientists and faculty in the Center for Research in Water Resources and the Department of Civil Engineering of the University of Texas at Austin. In addition, some materials are included that come from the Engineering Computer Graphics Laboratory of Brigham Young University (WMS and GMS), and from the Applications Programming Group at ESRI (watershed delineation tool in the Terrain module).

GISHydro97 Highlights

GISHydro97 is a synthesis of some of the products of our GIS Hydrology research program into a coherent form in which they will form a more secure basis for development of understanding and application of GIS to hydrology and water resources problems. GISHydro97 includes:

In all, GISHydro97 contains 530 MB of information presented in 4800 files organized into 250 directories. It covers all the major phases of the hydrologic cycle, deals both with water quantity and water quality, shows how to use a map database to link models of different processes operating within a given environment, and shows examples of applications at many spatial scales ranging from project sites and watersheds within a city, to State and regional level analyses, and also studies of some of the world's largest drainage basins. Some of the models deal with steady state or mean annual conditions, some deal with monthly time periods, others with daily or hourly data. There are more than 20 comprehensive instructional exercises, each 10 to 20 pages in length, which explain how to process the data using Arcview and Arc/Info and the tools provided on this CD-ROM. This is the single most comprehensive source of digital information on GIS Hydrology that has been produced to date.

GISHydro97 Limitations

It should be understood that the material contained here in the GH modules is the product of a research program and is not intended to be a fully supported software system. A contact person is named for each module to whom questions can be addressed or they can be addressed to me personally, by email at While we have taken great care in our research and coding to be accurate and rigorous, we make no guarantee that these modules are error free. We intend for the tools, exercises, data, and references presented here to stimulate thinking and to create confidence that secure technology can be created in this field, but there is a considerable difference between prototype tools as presented in the GH Modules, and formally engineered software systems, as GMS and WMS are.

Each of the GH modules is independent of the others although some can share data directly and others can share data through map transformations from one spatial framework to another. The code for the WMS and GMS tools from Brigham Young University is not included here as the developers of those systems want users of GISHydro97 to access their Engineering Computer Graphics Laboratory web page so as to download the most recent versions of their products, which are fully supported software systems with licenses, help lines, etc. The Map Modules linking WMS and GMS with Arcview and Arc/Info are still being developed, so the current versions of those systems are not able to directly read GIS files.

Some of the GH modules are still evolving, in particular, the Soilwater and Rivers modules, so several exercises are presented showing alternative approaches to solving the problems. The methodology underlying these systems is to some degree still being worked out, especially in so far as the hydrologic methods are adapted for dealing with spatial data. This is an ongoing process.

Also, this is our first attempt at producing a comprehensive information product on CD-ROM that mixes a number of different types of information, and it is likely that there will be problems and bugs, some of which we know about now and others which will be discovered later. We intend to maintain a GISHydro97 page on internet ( to present advances in the modules as they are created, and to document known problems and fixes for them. One problem that we've already run into is that files copied with a File Manager tool from a CD-ROM are labelled ReadOnly and thus are not executable by Arcview. We've found a work around to this using DOS XCOPY that is documented at several places on the ROM.

History of the Research Program

For the reader unfamiliar with our program, it may be useful if I briefly describe the history of how we reached the point of being able to produce this CD-ROM. About 15 years ago, I served as the drainage engineering consultant of a small community, Rollingwood, Texas, and it was my responsibility to examine the plans for new subdivisions and commercial buildings in the city to see if the plans complied with the city's drainage laws. I worked with maps, construction plans, and computer program outputs from the HEC-1 and HEC-2 computer programs to define flood discharge rates and water surface elevations and the effects of new developments upon them. It occured to me that the various components of this task were computerized (except for maps at that time) but that no connections existed between the graphical and computational elements of this task. I spent much of my time as a regulator checking that data had been correctly transcribed from drawings and maps to the input files of computer programs. That seemed like a job for machines rather than people!

In 1986, I initiated a research program with the general idea of linking graphical representation of the land surface with models which described water movement across the land surface. One of the graduate students who worked on that first project was Norman Jones, who after obtaining his PhD in our Department of Civil Engineering, returned to Brigham Young University, where he has built up an impressive suite of surface and groundwater flow modeling programs linked to a common graphical user interface in the Engineering Computer Graphics Laboratory, with the cooperation of the Hydraulics Laboratory, Waterways Experiment Station of the US Army Corps of Engineers. Over the past couple of years, we have been assisting Norman and his associate Jim Nelson to prepare a Map Module for their programs so as to facilitate transfer of Arc/Info and Arcview data files to and from their programs. This map module is presently in the testing stages but as time evolves the new versions of their software will contain a secure linkage to GIS data files.

By 1989, I had become convinced that we needed to have a more comprehensive software and hardware environment to accomplish the goals that I envisaged, and I met Jack Dangermond, President of ESRI, at an American Society of Civil Engineers conference in Atlanta. Subsequently, we began using Arc/Info in our research program, and Dean Djokic was the first PhD student who worked with me in this area. After completing his PhD and spending a period in academia, Dean is now responsible for hydrology in the Applications Programming section of ESRI in Redlands, California, along with Zichuan Ye, another PhD graduate of our program who also works at ESRI, Redlands. Dean and Zichuan are conducting a project to develop a better watershed delineation tool and the current version of this tool, still under development, is contained in the GISHydro97 Terrain module.

By 1991, I decided that I could not fully understand what my students were doing in their GIS-related research without a better understanding of the software, and what better way to learn a subject than to teach it! So I started a graduate course, GIS in Water Resources, first taught in the Spring Semester, 1991, which has continued each Spring since, the 1997 version being its seventh presentation. I used this course to synthesize the knowledge from our research program into a form that could be systematically used by classroom students. The first few times I taught this course, I used the Understanding GIS: the Arc/Info Method, the outstanding book from ESRI describing the basics of data development in GIS. In 1992-93, while I was on sabbatical leave at Stanford University, I used this book to present the first GIS course taught at that University. Based on the knowledge I developed during my sabbatical leave, in 1994 I began to develop new course exercises on the use of GIS in hydrology and water resources, focussed on data development from existing digital sources and the application of spatial hydrologic models. This Exercise format for homeworks has proven to be an effective method of showing how to conduct GIS-based analysis of various kinds such that a class of students, given a particular task, can work through the task on their own, and accomplish the desired result. GISHydro97 contains more than 20 exercises of this kind demonstrating the application of the various tools.

The advent of the Internet, first as a source of spatial data, then later as a method of conveying text and images, has provided a tremendous boost to the application of GIS in any field. In Spring 1996, I converted my class exercises from paper to html and presented made their data available on anonymous ftp so that GIS users outside the University could learn along with my students in what I've called the Internet Classroom. I believe that this opportunity of breaking down the walls of our classrooms and making the knowledge freely available to whoever needs it, is a vital way in which the University can be more effective as a source of enlightment to the wider society, not just in Texas or the United States but throughout the world. And greater knowledge, I hope, leads to better democracy and better lives for humanity.

Research Supporting GISHydro97

I have always had an interest in being an educator of the world, and in 1994 I initiated a cooperation with the Land and Water Development Division of the UN Food and Agriculture Organization, and and the Division of Water Sciences of UNESCO, in a project called the FAO/UNESCO Water Balance of Africa. This project involved cooperation with the government of Morocco, and in November 1996, Seann Reed and I presented a 3-day short course on GIS in Water Resources in Rabat, Morocco, for which a series of six exercises were prepared in English, and translated into French, and subsequently into Spanish. These FAO/UNESCO Water Balance of Africa Exercises are presented on this CD-ROM along with their data files. This work is greatly aided by the production by the US Geological Survey of GTOPO30, a 30" digital elevation model of the earth. As part of this work, we compiled from existing data sources monthly precipitation, temperature, solar radation and soil data on a 0.5 degree grid over the earth, and those data were assembled by Sandra Akmansoy and presented on GISHydro97 in the first version of a Digital Atlas of the World Water Balance. Much of the understanding in the Terrain, Soilwater and Rivers modules of GISydro97 is drawn from this FAO/UNESCO supported research. Francisco Olivera, Zichuan Ye, Seann Reed, and more recently Kwabena Asante have done the key research on this project. I am also grateful to my faculty colleage, Daene McKinney, who is actively cooperating in this international work. Zichuan Ye's PhD dissertation documents much of this work.

A traditional goal of the hydrology community has been to link GIS and hydrologic modeling so as to support hydrologic modeling with spatial data. Our work in this area has been fostered since 1992 by a series of research grants from the Hydrologic Engineering Center of the US Army Corps of Engineers, in Davis, California. HEC is a widely respected hydrologic modeling center whose HEC models are a standard in the field. Beginning with investigations by Seann Reed into the use of Nexrad precipitation data and continuing more recently with the work of Ferdi Hellweger on HEC-Prepro, a hydrologic preprocessing system for GIS data (presented as the GISHydro97 Prepro module), new techniques and code have been produced in prototype form at the University of Texas, and in the case of the Nexrad tools, taken further into a more formally engineered set of software tools by Tom Evans, who also received his PhD in our program and who is now the GIS hydrology specialist at HEC. A separate contribution to this field was made by Peter Smith's Masters thesis in which he developed a Hydrologic Data Development System, an integrated package of data sets for Texas and AML programs to interrogate them and provide hydrologic model inputs. This work is being further carried on by Francisco Olivera and Juling Bao.

Water quality has been another theme in our research, advanced in particular by the research of Bill Saunders, Jennifer Benaman, Pawel Mizgalewicz, Ann Quenzer, Ferdi Hellweger and Christine Dartiguenave. Bill Saunder's Masters thesis was the prototype of using mean annual annual analysis of runoff and pollution loadings, an approach emulated in several later projects. Jennifer Benaman's Masters thesis showed how to link GIS-based land surface loadings with a standard water quality model. Pawel Mizgalewicz is a pioneer in the development of integrated spatial databases to support hydrologic and water quality modeling and his PhD dissertation documents many new ideas in this field. Ferdi Hellweger is the developer of the Balance model for receiving water quality computation, as described in the Quality module. Francisco Olivera's PhD dissertation shows how to do spatially distributed and time varying runoff and water quality simulation. Tom Evan's PhD dissertation develops a spatially distributed statistical methods for analyzing groundwater quality. Ann Quenzer and Christine Dartiguenave are current MS students who are furthering these ideas, as described in the GISHydro97 Loads and Quality modules. We are particularly grateful for the cooperation of the Texas Natural Resource Conservation Commission, the Corpus Christi Bay National Estuary Program and the City of Austin in this research.

I have had a long-standing interest in the movement of atmospheric water, believing that the study of hydrology should begin not with precipitation, but with the movement of water into a region in the atmosphere which forms the source of the precipitation. This research was originally carried out by Jerome Patoux, and more recently continued by Cindy How, Zichuan Ye, and Seann Reed. The data that are presently available on atmospheric water are in some cases not precise enough to permit reliable computations of the atmospheric water balance on a regional basis, but as measurement and modeling of the atmosphere improves, these data will become more precise. This research forms the basis of the GISHydro97 Atmosphere module.

Besides the people that I've mentioned previously, a number of other people have contributed to the ROM, either by preparing materials, or serving as checkers. Each module has a preparer and also an independent checker to verify the procedures contained in it. These individuals include:  Juling Bao, Karen Boles, Nabil Eid, Lesley Hay Wilson, Chul Kim, Mike McAdams, Kris Martinez, Carolyn Nobel, Maggie Ye Ruan, and Dean Thomas. I am grateful for the contributions of all the members of the GISHydro97 production team.

The sponsors of the reseach reported on GISHydro97 include the United Nations Food and Agriculture program, UNESCO, US Environmental Protection Agency, US Department of Agriculture, US Geological Survey, US Army Corps of Engineers Hydrologic Engineering Center, US Army Corps of Engineers Waterways Experiment Station, US National Committee on Scientific Hydrology, Texas Water Resources Institute, Texas Natural Resource Conservation Commission, Texas Water Development Board, the Corpus Christi Bay National Estuary Program, and the City of Austin, Texas.

Concluding Remarks

As I have become better acquainted with GIS, I believe that this technology offers a significant opportunity to the hydrology community to rethink the way that we have been conducting our analyses, to augment the traditional approach with new spatial data sources so that we can get a better understanding of processes in time and space. During the 1980's I co-authored a textbook Applied Hydrology; from 1989 to 1993 I edited the Handbook of Hydrology, a 1400-page compendium of knowledge in all fields of hydrology; and from 1992 to 1995, I was Editor of the Journal of Hydrology. The broad spectrum of thinking to which these publications exposed me, and the parallel experience of developing the teaching and research program applying GIS to this field, have created some insights as to how new approaches to hydrologic problems using spatial data can be made, which are reflected in the various components of GISHydro97. During this period I was much encouraged by participation in the series of International Conferences on GIS and Environmental Modeling organized by the National Center for Geographic Information and Analysis in 1991, 1993 and 1996. These conferences brought together representatives of the GIS community interested in environmental modeling and through them I gained a deeper understanding of the perspective of geographers and of biological and earth scientists in this field. I hope that the research, data and teaching materials presented here will be helpful to the wider GIS and hydrology communities to take advantage of the knowledge developed in our program and to further broaden and deepen this field. I believe that we can use this approach to readily produce more accurate answers to hydrologic problems at lower cost than by traditional means, and that we can reach across spatial scales to build models that work from maps of any size of hydrologic system, ranging from small sites to huge river basins. This is a grand challenge, worthy of our best endeavors.

The intent of this description of how our program evolved is to show that the components that are presented on GISHydro97 arose from a combination of research and teaching activities that involved a large community of people working cooperatively with many institutions over a long period of time. It goes without saying that I am grateful to all the people whom I have identified in this discussion, and to the many others whom I have not identified by name but who have never the less played an important role in cooperating with our program. I want in particular to acknowledge the contribution of Francisco Olivera who is my key support person in all areas of research and teaching, and whose work underlies several of the GISHydro97 modules. I would also like to pay a tribute to ESRI which has been a congenial and supportive research partner for many years. In particular, I want to acknowledge the cooperation of Jack Dangermond, Scott Morehouse, Steve Kopp and Witold Fraczek of ESRI. Steve Kopp has been the key person who has helped me to present the GIS Hydrology workshops at the ESRI User Conferences and I appreciate all the effort that he has put into that endeavor. I hope that you will find this GISHydro97 CD-ROM enlightening and useful.

David R. Maidment

These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 1997 Center for Research in Water Resources.