Journal of Water Resources Planning and Management

Using geographic information systems (GIS) technology as an underlying platform for hydrologic and hydraulic models provides an effective mechanism for performing large‐area surface water and drainage management studies. An early (1984) personal computer (PC)‐based application of GIS technology, combining various commercial software packages, was used to develop a surface water management plan (SWMP) for Polk County in central Florida. At the time of the study, no fully featured GIS package designed to support hydrologic/hydraulic modeling existed on PC platforms. Therefore, a combination of technologies was used, including a computer‐aided design (CAD) package, a commercial data‐base management system, and a raster‐based GIS software package. The HEC‐1/HEC‐2 models were linked to these packages through custom programming in order to perform the required hydrologic/hydraulic analyses. Ten separate scenarios were examined for each of the 784 subbasins comprising the study area, an extensive modeling effort that would not have been possible without the supporting GIS technology.

The use of geographic information systems (GIS) for spatial hydrologic data analysis has provided many benefits for water resources permitting and design. This paper discusses a computer model, developed to aid phosphate mine— reclamation design, as an example of the means and real benefits to be derived by incorporating GIS into hydrologic modeling. The model integrates a commercial GIS, public‐domain surface‐water and ground‐water hydrologic models, and a specially written evapotranspiration code to be run on a microcomputer within a highly structured interface. The user community consists of state and local regulatory agencies, mining companies, and private consultants. The GIS provides an important spatial/analytical function, performing the time‐consuming georeferencing and spatial overlays (GIS modeling) to develop input data as well as providing a mechanism to link the surface‐water and ground‐water codes written with disparate spatial discretizations. This paper supports the premise that the incorporation of GIS into hydrologic modeling provides for an increased detail of evaluation, minimizes user subjectivity in parameter selection, and reduces costs of analysis due to significant time savings.

Nonpoint‐pollution models estimate loadings of chemicals, sediment, and nutrients that degrade water quality. Before controls can be implemented, location and severity of pollution must be identified in the watershed basin. Geographic information systems (GISs) are computer‐automated, data management systems simplifying the input, organization, analysis, and mapping of spatial information. Because nonpoint‐pollution models simulate distributed watershed basin processes, a heterogeneous and complex land surface must be divided into computational elements such as grid cells. Model parameters can be derived from each grid cell directly from maps using GIS. Cell size selection, if arbitrarily determined though, yields ambiguous if not erroneous results. This paper investigates the effects of cell size selection through a sensitivity analysis of input parameters for the nonpoint‐pollution model, Agricultural Nonpoint Source Pollution Model (AGNPS), using a GIS for a small research watershed. Model grid‐cell sizes were found to be the most important factor affecting sediment yield. As the grid‐cell sizes increase, stream meanders are short‐circuited. The shortened stream lengths cause sediment yield to increase by as much as 32%.

Spatial decision support systems (SDSSs) are a new class of computer systems that combine the technologies of geographic information systems (GISs) and decision support systems (DSSs) to aid decision makers with problems that have a spatial dimension. DSSs consist of a user interface, model base, and data base, are designed to help solve complex problems, and are oriented toward decision makers. The spatial analysis and display capability of GISs can improve each component of a DSS and have enabled the evolution of DSSs to SDSSs. The SDSS concept and architecture is well suited to merging GISs and DSSs, including water resource models that are part of water resource DSSs. The success of SDSSs in water resources will require the collaboration of GIS developers, water resource modelers, DSS designers, and water resource decision makers to accept the challenges arising from the integration of these technologies. Future action should include research on user interfaces, data‐base methods, adapting models to SDSSs, the development of a taxonomy of methods for the model base of SDSSs, and developing prototypes to demonstrate and test the SDSS concept.

The feasibility of using an expert geographic information system (GIS) for long‐term regional water‐resources planning is evaluated through a case study examining an existing regional water‐supply system. This system is comprised of an expert system that embodies the logical rules and expertise of water‐resources planning experts as well as a geographic information system that stores and analyzes spatially distributed data. Normal water‐demand forecasts and water‐supply data along with appropriate analysis routines are used in this new planning tool, which attempts to follow the logic of current methods and permit plans to be updated and alternatives to be analyzed more rapidly. An example application of the system is presented which analyzes the existing water supply system for the Corpus Christi, Tex., area. Given annual yields for the reservoirs, water‐demand forecasts, and institutional requirements, the expert GIS calculates potential water‐supply deficits or excesses in the region over a 50‐year planning horizon, and suggests efficient and cost‐effective alternatives for developing additional water supplies in the event that deficits occur.

The geographic information systems (GIS) implementation process starts with the initial decision to use a GIS; proceeds through system selection, installation, and training; and up to data‐base development and product generation. This paper discusses considerations related to each phase and focuses on other facets of GIS pertinent to water‐resources planning and management. Many of these considerations involve critical choices that can pose significant challenges and impose substantial costs. An understanding of these challenges can expedite the GIS implementation process.

Increasing use of distributed, physically based urban storm water management models requires urban water managers to acquire, maintain, and utilize the extensive, spatially referenced data bases necessary to support these efforts. Geographic information systems (GIS) are ideally suited to preparing, storing, updating, analyzing, and displaying these data in conjunction with urban storm water modeling. A physically based urban storm water runoff model is linked to a low‐cost, PC‐based raster GIS package to facilitate preparation, examination, and analysis of spatially distributed model inputs and parameters. Impacts of urban storm water management strategies are analyzed through preprocessing by GIS, calculation of discharge by the urban runoff model, and postprocessing and display of spatial output in the GIS. Three methods of encoding urban features in a raster GIS system are utilized: single value attributed data (SVAD), edge probability attributed data (EPAD), and central attributed raster line (CARL). The viability of the raster GIS/urban storm water model linkage in a microcomputing environment is demonstrated on a study area in the Greenbriar subdivision in Fort Collins, Colorado.

Network routines are implemented within several geographic information systems (GISs). These routines are primarily used in traffic routing and allocation analyses, and very little work has been done on their application in water resources. This paper describes Dijkstra's algorithm, which is used for most network implementations in a GIS and how its routing and allocation techniques can be implemented for water flow and transport. Dijkstra's algorithm is limited by the fact that it requires the resistance to flow be known before the magnitude of the flow is determined, but these two variables are usually interdependent. The consequences of this limitation with regard to water‐resources applications is discussed. The types of problems suitable for GIS water‐network analysis are identified. Three applications—drainage‐network verification and sizing using rational method, watershed isochrone determination, and steady‐state flow computations—are discussed in detail, and their network application within the Arc/Info GIS is presented. These applications are embedded directly within a GIS, thus simplifying the modeling environment.

Geographic information systems (GIS) provide a digital representation of watershed characteristics used in hydrologic modeling. This paper summarizes past efforts and current trends in using digital terrain models and GIS to perform hydrologic analyses. Three methods of geographic information storage are discussed: raster or grid, triangulated irregular network, and contour‐based line networks. The computational, geographic, and hydrologic aspects of each datastorage method are analyzed. The use of remotely sensed data in GIS and hydrologic modeling is reviewed. Lumped parameter, physics‐based, and hybrid approaches to hydrologic modeling are discussed with respect to their geographic data inputs. Finally, several applications areas (e.g., floodplain hydrology, and erosion prediction) for GIS hydrology are described.

The U.S. Environmental Protection Agency (EPA) has developed a geographically referenced data‐base system of the surface‐water features of the United States. This data‐base system is called the Reach File. It was designed to serve as a foundation for water‐quality modeling, for storing and using stream‐network information, for topologically indexing other water‐resource data bases so that they may be accessed within a common analytical framework, for generating digital base maps of hydrographic features in user‐selected areas for water‐quality reporting and analysis, and for producing gazetteers of streams, lakes, and open waters. The Reach File serves as a cornerstone for data integration in EPA water programs, and as a major geographic information resource for water‐quality modeling and analysis. This paper briefly describes the Reach File and a system called the Routing and Graphical Display System (RGDS) that uses the Reach File and associated files to model and display water quality. The combination of the Reach File System and the modeling and display capabilities of RGDS may be viewed as a specialized network‐oriented geographic information system for surface‐water‐related analyses.

The protection of areas that contribute water to public wells (wellhead protection areas or WHPAs) is an important component of the Rhode Island Department of Environmental Management (RIDEM) ground‐water protection strategy. An accurate, scientifically based WHPA delineation is the first step in wellhead protection. RIDEM has chosen to use the Uniform Flow analytical model, in conjunction with hydrogeologic mapping, for WHPA delineation around large public supply wells completed in stratified drift in Rhode Island. Geographic information system (GIS) calculates variables for input into the model, transforms model output into geographically referenced data layers, and provides mylar overlays for final hydrogeologic mapping of the WHPA. RIDEM hydrogeologists provide study area boundaries, run the model on a personal computer‐ (PC‐)based program, and delineate the final WHPA on mylar overlays. Maps of the WHPAs and other hydrogeologic data will be provided to communities and water suppliers and will be the basis for local wellhead protection planning required under the Rhode Island Wellhead Protection Program.