ArcGIS Data Models: Water Utilities - Esri

W ATER NETWORKSlarge; the network system is relativelysimple; and the networks can spanhundreds of miles as they push waterover continental divides, under oceanchannels, and across deserts topopulation centers.As the transmission system deliverswater to a community, the transmissionsystem connects with the local waterdistribution system. Usually, there aretreatment plants that ensure waterquality and control the flow of waterinto the distribution system. Manytreatment plants also have adjacentstorage basins and enclosed storagefacilities to provide adequate flowwhen water demand exceeds thecapacity of the transmission system.Typical devices include pumps,chemical injectors, aerators, motors, and generators.Design discussionRadial and looped networksIn addition, the object model is readily extensible,allowing developers to extend the model, behavior,and user interface of the system with minimaleffort.There are two primary types of networks: radial andlooped. Radial networks are best represented by streamdrainage and storm drainage networks. Flow always hasan upstream and downstream direction that branchesout/in. Looped networks, on the contrary, frequentlyself-intersect. Water distribution networks are loopednetworks by design to ensure that service interruptionsaffect the fewest customers.radial networklooped networkTRANSMISSION SYSTEMSAround the world, the water that we consume forresidential, commercial, and industrial purposesoriginates from a source, usually in the form of alake, river, or underground aquifer. Forcommunities that do not have a local water supply,a transmission network is built to transport the waterfrom the source to the destination communities.Transmission systems are typically composed ofaqueducts, tunnels, connecting devices, andpumping facilities. In a transmission system, all ofthe pipes, devices, and pumping facilities tend to beSewer and stormwater networks are typically radialnetworks, but there are often flow splits and overflowcapabilities to provide additional capacity for times ofpeak network load. Sewer and stormwater networks arealso unique because streets and pavement are speciallydesigned to function as a secondary stormwater systemduring flooding and heavy rainfall.4 ArcGIS Water Utilities Data ModelCh01 Modeling.p65412/05/2001, 1:12 PM

DISTRIBUTION SYSTEMSThe distribution system typically involves a muchsmaller geographic area, but the complexity of thenetwork is much higher than the transmissionnetwork. Water distribution systems are consideredlooped networks because they are designed to providea continuous flow of pressurized water throughoutthe network, even when some sections of thenetwork are temporarily isolated for repair andreplacement activities. The looping of the networkalso tends to provide for pressure equalizationthroughout the water network. Operating watersystem valves can isolate areas of the waternetwork. The looping of the water mains requiresfittings such as tees and crosses to connect multiplepipes at a junction. Other fittings, such as couplers,bends, and reducers, permit the connection ofseparate physical pipe segments.ServicesUltimately, water is distributed to residential andcommercial water customers. Often, tapping sleevesare employed to connect ¾" to 1 ½" service pipesto a 6" or larger water main to provide residentialservice. For larger services, tapping sleeves may beused for connecting fire hydrant and fire services,but tees are often used as well. Typically, thesehydrant and fire service connections will have a6–8" diameter to provide enough flow for firesuppression purposes. Most commercial andresidential services are metered for billing purposes.Fire services and fire hydrants are rarely metered.Water utilities need to classify their networkinventory reporting to distinguish normal systemvalves from hydrant valves when the physicaldevice is the same piece of equipment. Similarly,large industrial water consumers often own thewater mains and hydrants surrounding theircomplexes. The equipment is exactly the same asother hydrants, but the ownership of the facilitiesis important from a plant accounting and assetmanagement standpoint.Network managementWater utilities often manage pipe segments in differentways at different times. For example, if a coupler isused to simply connect two short sections of pipe fornew construction and the characteristics of eachphysical pipe are identical, most engineers wouldconsider this to be a single pipe segment. On the otherhand, when an inline renewal is performed and acoupler joins an older piece of 8" steel pipe to a newpiece of 8" PVC pipe, these would be considered twodifferent pieces of pipe. Managing these logical pipesegments, including associations with customerservices and other network features, requires asophisticated GIS application.Furthermore, the condition of mains is consideredfor logical sections of pipe in water networks. Thecondition of water mains is usually calculated usinga combination of leak and repair information alongwith the estimated life span of pipes according tofactors such as material and installation date. Thephysical condition of sewer mains is usually judgedbetween manholes and linked to a video index. Thecondition of sewer mains is usually determined byoperations staff using internal videos of the sewernetwork and rating pipe conditions according tovisual characteristics.Modeling with the ArcGIS Water utilities data model 5Ch01 Modeling.p65512/05/2001, 1:12 PM

From an inspection, maintenance, and repair perspective, the association of all relevant operations activitywith the physical device throughout its life at varioustransient geographic locations is also important.Customer billing/demand information is important forsystem capacity planning. There are many sophisticatedsoftware products available today to perform complexhydraulic analysis that requires a combination offacility and customer demand data. Water andwastewater utilities need an effective way to performsystem planning through linking the current GISnetwork with consumption data.SEWER AND STORMWATER NETWORKSOperations and maintenanceAt the operations and maintenance level, valves,meters, hydrants, and other facilities are oftenremoved from the network, for maintenance orstorage, and then later installed in a new geographiclocation. This creates further complications for waterasset management. For accounting purposes, utilitiesdepreciate new facilities from the time these facilitiesare installed in the ground. The manner in whichrecovered materials are depreciated is significantlybetween new and recovered facilities.Design discussionWater modeling requires consideration of facilitiesas assets.One benefit of GIS technology is that utilities can tracktheir assets by geographic location. Network assets, likemost other infrastructure owned by businesses, can bedepreciated for tax accounting purposes. The specificamount of depreciation allowed depends on the originalvalue of the equipment, how long the facilities have been inthe ground, and the tax boundary area that the facilities arelocated in. Having an accurate record of facilities managedwith a GIS provides a more accurate inventory of existingfacilities and an automated way to maintain these recordsas a by-product of map maintenance activities. From a GISsystem design standpoint, it is important to understandhow the exact same piece of physical equipment (i.e., thesame 10" valve) can be considered differently from an assetmanagement standpoint, depending on if the valve is usedas a normal mainline valve or as a hydrant valve. You shouldconsider asset management in your geodatabase design andalso any special rules that your utility may require for assetmanagement.As water is consumed in each home and business,wastewater is introduced via laterals into the sanitarysewer system. The basic physical components of thewastewater collection network are similar to the waterdistribution network.In a similar way, water enters the stormwater collectionsystem through curb inlets, catch basins, streams,ditches, and culverts. A combined sewer system intermixes stormwater runoff and wastewater during peakrunoff periods. Historically, these combined sewerswould flow untreated into rivers, lakes, and oceans.While very few combined sewer systems are being builttoday for environmental reasons, many communitiesare actively separating their sewer and stormwatersystems with massive capital improvement programs.A key characteristic of most wastewater andstormwater collection systems is that they are almostDesign discussionConsider the requirements for logical andphysical segmentation of pipe networks forfacilities management.ArcGIS allows you significant flexibility with the logicaland physical segmentation of your pipe networks. Insteadof relying on traditional arc–node topology, ArcGISprovides a set of network features: simple junctions, simpleedges, complex junctions, and complex edges. The ArcGISdocumentation describes the network feature classes inmore detail, but the key point is that you have manyoptions for implementing a more flexible topology modelwithout having to write complex applications to manageyour data.6 ArcGIS Water Utilities Data ModelCh01 Modeling.p65612/05/2001, 1:12 PM

always gravity fed. Sewer systems are generally connected at manholes to provide for rudimentary flowcontrol and connection of pipes at different elevations. This key distinction results in modeling waternetwork elevations with fittings and valves, whilesewer network elevation information is captured atthe ends of pipe segments.Eventually, sewer systems terminate at treatmentfacilities or outfalls into natural watersheds. While thepurpose and composition of these treatment plants isvery different than treating potable water, there arestrong similarities between the kinds of devicespresent in sewer structures and water structures from aGIS modeling perspective.Common characteristicsAll water systems have basic supporting features thatdo not actively participate in the distribution ofwater. Casements, vaults, meter boxes, SCADAsensors, sampling stations, and cathodic protectiondevices perform important functions, but the networkcould function without these pieces of equipment.Water flows downhill in sewer systems in what iscommonly referred to as a radial network. This meansthat water entering the system at any one point willtravel the same network path to reach a treatmentfacility, discharge point, or retention pond. At lowpoints in topography, lift/pumping stations are used topush water over hills and other obstacles. These forcedmain networks are almost identical to comparablewater distribution facilities, so there is significantmodeling overlap between the systems as a result.Design discussionDevices such as hydrants and valves are oftenmoved to different locations during their life span.During the lifetime of a particular valve, hydrant, or similarfacility, the individual piece of network equipment may beinstalled in one location. This equipment may eventuallybe removed for maintenance and storage for a period oftime. This process can be repeated for the same piece ofequipment several times during its lifetime. From an assetmanagement standpoint, an accurate accounting fordepreciation purposes is important. It is also important tolink historical maintenance, repair, and inspection data todetermine when the equipment has reached the end ofits reliability curve.Design discussionConsumption data from customer billingsystems is often required on networks forexternal modeling purposes.Most network analysis software products will requirecustomer consumption/demand information for systemmodeling. Usually, this information is stored in a utility’scustomer information system. Being able to link customerdemand to network features via customer connectionpoints is valuable for network analysis and thematicmapping purposes. The model introduces a specialnonmaterial feature class called a lateral point to define aphysical location on the network that represents a singlerecord in the customer information system. This featureclass was created to handle the various types ofcustomer account records. It is anticipated that updatesto the Customer Information System (CIS) and GIS maybe several weeks or months out of step with each otherfor most utilities, so any implementation that integrates aCIS and a GIS at your utility should be developed basedon your specific needs.Modeling with the ArcGIS Water utilities data model 7Ch01 Modeling.p65712/05/2001, 1:12 PM

Design discussionLinking operations data to GIS networks isimportant for assessing pipe quality andprioritizing improvement projectsVisualizing operations data, such as leaks, repairs,maintenance, and inspections, is important for assessingpipe/facility conditions and prioritizing capital improvement projects. For example, water main segments thatexceed a certain number of leaks per unit of lengthshould automatically be replaced. Many nongraphicalasset management systems can handle this simple task.The value of GIS is the ability to see patterns in the datasuch as areas of moderate pipe condition, where thereare multiple pipes running down the same street orcrossing the same intersection. What might appear to beareas of low priority without a map can easily beidentified as high-priority areas when the network isvisualized using GIS. As a result, utilities can moreeffectively utilize capital improvement budgets.Beyond the basic network information, the ArcGISWater model can easily be extended to include a fullrepresentation of customer information databases,operations databases, and asset databases. The coremodel, however, simply provides the ability to linkthe features in the geodatabase to external systemsvia an external system identifier since most modernutilities already have systems to support thesebusiness needs.8 ArcGIS Water Utilities Data ModelCh01 Modeling.p65812/05/2001, 1:12 PM

2Deploying theArcGIS Waterdata modelArcGIS Water provides a large set ofcomponents that you can use to implementyour data model. The ArcGIS Water model canbe deployed with no modifications or can behighly customized to fit your system’s specificrequirements.Topics discussed in this chapter: The process of deploying ArcGIS Water Implementation resources Geodatabase basics Defining your geodatabase requirements Selecting an implementation process ArcGIS deployment scenarios9Ch02 Deploying.p65912/05/2001, 1:14 PM

THE PROCESS OF DEPLOYING ARCGIS WATERThis chapter provides a conceptual overview of theprocess of deploying ArcGIS Water, beginning with anoutline of the process, then discussing each of thestages in more detail. The chapter ends with twoscenarios for implementing custom geodatabases. Atseveral points in this chapter you will be referred tothe books Modeling Our World, Using ArcCatalog, andBuilding a Geodatabase for more information. You mayfind it useful to have these books at hand forreference.Stage III: Sharing your geodatabase1. Create connections to the database.The core of ArcGIS for Water is a set of objects thatyou use to create sophisticated models of your watersystem. With these objects you create a geodatabasethat stores geographic features and tables as objectswith behaviors and relationships. You use the desktopapplications ArcMap and ArcCatalog to view,edit, and manage your geodatabase. You use theincluded map templates, layers, and styles to symbolizefeatures and create maps of your faci

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