GIS Applications for Water, Wastewater, and Stormwater Systems - Chapter 12

CHAPTER 12 Water Models GIS saves time and money in developing water distribution system hydraulic models for simulating flows and pressures in the system. GIS also helps in presenting the model results to non-technical audiences. EPANET and ArcView GIS integration. Copyright © 2005 by Taylor & Francis LEARNING OBJECTIVE The learning objective of this chapter is to understand how GIS can be applied in developing water distribution system hydraulic models and presenting the results of the hydraulic models. MAJOR TOPICS · Development of hydraulic models · Software examples · EPANET model · Network simplification (skeletonization) · Estimation of node demands · Estimation of node elevations · Delineation of pressure zones · Mapping the model output results · GIS application examples and case studies LIST OF CHAPTER ACRONYMS AM/FM/GIS Automated Mapping/Facilities Management/Geographic Information System CIS Customer Information System COM Component Object Model COTS Commercial Off-the-Shelf DEM Digital Elevation Model DHI Danish Hydraulic Institute DLL Dynamic Link Library DRG Digital Raster Graphic GEMS Geographic Engineering Modeling Systems MMS Maintenance Management System ODBC Open Database Connectivity PRV Pressure Regulating Valve SCADA Supervisory Control and Data Acquisition TIF Tag Image File CITY OF GERMANTOWN’S WATER MODEL Application GIS software Other software GIS layers Hardware Study area Organization Water distribution system mapping and modeling ArcGIS, ArcGIS Water Utilities Data Model (formerly ArcFM Water Data Model), and MapObjects WaterCAD Digital orthophotos, pipes, hydrants, valves, manholes, pumps, meters, fittings, sampling stations, and monitoring wells Two Dell Precision 220 computers City of Germantown, Tennessee City of Germantown, Tennessee The City of Germantown (Tennessee) water distribution system serves 40,000 people through 12,000 installations in a 17.5 mi2 area. The system has approximately 95,000 ft of water pipes. Copyright © 2005 by Taylor & Francis The City used ESRI’s geodatabase, an object-oriented GIS data model, to design a database. The database design was done with minimal customization of ESRI’s ArcGIS Water Utilities Data Model. This approach helped complete the database design in a few weeks instead of several months. ESRI’s MapObjects was used to create a custom utility tool set for developing the water distribution network. Valve and hydrant locations from the digital orthophotos and planimetric mapping were used with the existing1in.= 500 ft-scale paper map of the water system as the basis for connecting water pipes. The GIS layers (Figure 12.1) were initially developed using the ArcView Shape-files. The Shapefiles were then migrated to a geodatabase. To ease the data migration, connectivity rules were stored in ArcCatalog rather than directly in the model. ArcMap “flag and solver” tracing tools were used to ensure topological integrity of the migrated data. ArcMap also provided the City with out-of-the-box network analysis functionality such as tracing paths and water main isolation. For the development of the hydraulic model, the City did not have to create a modeling network from scratch. GIS was used to skeletonize the network for input to the Haestad Method’s WaterCAD 4.1 hydraulic model. Spatial operations available in ArcGIS were used to assign customer-demand data — obtained from the City’s billing database and stored in parcel centroids — to modeling nodes. Node elevations were extracted from the City’s DEM. The hydraulic model was run to assess the future system expansion and capital improvement needs of the City. The model indicated that the system needed a new elevated storage tank and a larger pipe to deliver acceptable pressure under peak demand conditions (ESRI, 2002b). GIS APPLICATIONS FOR WATER DISTRIBUTION SYSTEMS GIS has wide applicability for water distribution system studies. Representation and analysis of water-related phenomena by GIS facilitates their management. The GIS applications that are of particular importance for water utilities include mapping, modeling, facilities management, work-order management, and short- and long-term planning. Additional examples include (Shamsi, 2002): · Conducting hydraulic modeling of water distribution systems. · Estimating node demands from land use, census data, or billing records. · Estimating node elevations from digital elevation model (DEM) data. · Performing model simplification or skeletonization for reducing the number of nodes and links to be included in the hydraulic model. · Conducting a water main isolation trace to identify valves that must be closed to isolate a broken water main for repair. Identifying dry pipes for locating customers or buildings that would not have any water due to a broken water main. This application is described in Chapter 15 (Maintenance Applications). · Prepare work orders by clicking on features on a map. This application is described in Chapter 14 (AM/FM/GIS Applications). · Identifying valves and pumps that should be closed to isolate a contaminated part of the system due to acts of terrorism. Recommending a flushing strategy to clean the contaminated parts of the system. This application is described in Chapter 16 (Security Planning Vulnerability Assessment). Copyright © 2005 by Taylor & Francis Figure 12.1 Germantown water distribution system layers in ArcGIS. · Providing the basis for investigating the occurrence of regulated contaminants for estimating the compliance cost or evaluating human health impacts (Schock and Clement, 1995). · Investigating process changes for a water utility to determine the effectiveness of treatment methods such as corrosion control or chlorination. · Assessing the feasibility and impact of system expansion. · Developing wellhead protection plans. Copyright © 2005 by Taylor & Francis By using information obtained with these applications, a water system manager can develop a detailed capital improvement program or operations and maintenance plan (Morgan and Polcari, 1991). The planning activities of a water distribution system can be greatly improved through the integration of these applications. In this chapter, we will focus on the applications related to hydraulic modeling of water distribution systems. DEVELOPMENT OF HYDRAULIC MODELS The most common use of a water distribution system hydraulic model is to deter-mine pipe sizes for system improvement, expansion, and rehabilitation. Models are also used to assess water quality and age and investigate strategies for reducing detention time. Models also allow engineers to quickly assess the distribution network during critical periods such as treatment plant outages and major water main breaks. Today, hydraulic models are also being used for vulnerability assessment and protection against terrorist attacks. Hydraulic models that are created to tackle a specific problem gather dust on a shelf until they are needed again years later. This requires a comprehensive and often expen-sive update of the model to reflect what has changed within the water system. A direct connection to a GIS database allows the model to always remain live and updated. Denver Water Department, Colorado, installed one of the first AM/FM/GIS systems in the U.S. in 1986. In the early 1990s, the department installed the $60,000 SWS water model from the Stoner Associates (now Advantica Stoner, Inc.). Around the same time, Genesee County Division of Water and Waste Services in Flint, Michigan, started developing a countywide GIS database. The division envisioned creating sewer and water layers on top of a base map and integrating the GIS layers with their water and sewer models (Lang, 1992). GIS applications reduce modeling development and analysis time. GIS can be used to design optimal water distribution systems. An optimal design considers both cost-effectiveness and reliability (Quimpo and Shamsi, 1991; Shamsi, 2002a) simulta-neously. It minimizes the cost of the system while satisfying hydraulic criteria (accept-able flow and pressures). Taher and Labadie (1996) developed a prototype model for optimal design of water distribution networks using GIS. They integrated GIS for spatial database management and analysis with optimization theory to develop a com-puter-aided decision support system called WADSOP (Water Distribution System Opti-mization Program). WADSOP employed a nonlinear programming technique as the network solver, which offers certain advantages over conventional methods such as Hardy-Cross, Newton Raphson, and linear system theory for balancing looped water supply systems. WADSOP created a linkage between a GIS and the optimization model, which provided the ability to capture model input data; build network topology; verify, modify, and update spatial data; perform spatial analysis; and provide both hard-copy reporting and graphical display of model results. The GIS analysis was conducted in PC ARC/INFO. The ROUTE and ALLOCATE programs of the NETWORK module Copyright © 2005 by Taylor & Francis ... - tailieumienphi.vn