The ability of GIS software to quickly generate a limitless variety of custom

maps suited to numerous applications, along with its powerful data management

and querying capabilities, perfectly complements the modeling, calculation,

and scenario management capabilities of water resource modeling software.

Shapefile compatibility

The minimal functionality required for any type of compatibility between modeling

software and GIS is a method of data transfer between the two, and shapefiles

can provide this method.

Using shapefiles to transfer data between GIS and modeling software provides

significant advantages over simply using database files. Since geometric data

is stored in the shapefile, specifying coordinate data is unnecessary. In addition,

shapefiles are a native file format of GIS applications, so viewing and editing

the network within the GIS application is easy and convenient.

However, there are a number of drawbacks involved in using shapefiles to exchange

data between the platforms. One disadvantage is that, just as with a simple

database file transfer, this process involves data replication. Every time changes

are made to data in one application, the shapefile must be exported and reimported

into the other application in order to synchronize those changes between the


In fact, using shapefiles as a means of data exchange shares many of the disadvantages

involved with database transfer. Data contained in the shapefile’s database

file must still be linked to modeling attributes to give the data meaning, units

must be specified, and data collections that span numerous database fields,

such as patterns, cannot be easily transferred using shapefiles.

In addition, certain modeling elements are treated differently by GIS than

by modeling software – in GIS, pumps and valves are generally represented as

point elements, while in modeling applications they are regarded as links. This

disparity must be resolved manually by the user when transferring this data

between the applications. It also demonstrates the lack of real integration

between the applications that is inherent in using shapefiles here.

While shapefiles store coordinate data, they do not possess awareness of network

connectivity, which is a critically important aspect of water distribution models.

Knowing which pipes connect to which nodes is a vital component for expanding,

editing, and calculating the model.

Half of the integration equation is the ability to transfer the calculated

results produced by the modeling software into the GIS. However, GIS software

does not natively support timeseries data, so to bring the results of an extended

period simulation into the GIS, the results for each time step must be imported

separately. Depending on the length of the extended period and the duration

of the time step, this can mean importing hundreds of database files.

Using shapefiles to transfer modeling data means that the modeling software

and the GIS are not unified; they are disparate applications, dependent on the

user for the transfer, synchronization, and definition of data between them.

Creating a unified whole

While providing a level of interoperability between modeling and GIS applications,

shapefile transfer does not truly provide integration, nor the transparent and

seamless interaction implied by the defining phrase ‘unified whole’.

The GIS and modeling software run as discrete entities, causing data separation

that hinders the modeling process.

Even modeling applications that natively use shapefiles to store the model’s

network spatial data cannot truly be said to integrate with GIS software. The

level of compatibility certainly increases, but the actual element input data

and calculated results are stored separately from the shapefile in proprietary

output files that need to be manually linked to the shapefile. This requires

the same userdependent management, definition, and oversight that is required

for simple database and shapefile connectivity. This type of compatibility

likewise runs outside of the GIS, and still requires the manual initialization

of data when switching between the two applications.

The challenge of providing true integration between GIS and water resource

modeling software can only be met by synthesizing the packages into a unified

whole, and WaterGEMS does exactly that. By actually working within the GIS environment,

WaterGEMS modeling software unifies the packages within a common interface,

without limiting the functionality of either the modeling software or the GIS.

The strengths of each can be utilized without the need for repeated database

or shapefile export/import, field linking, or the reentry of data. All modeling

elements and data are accessible to all GIS tools and functionality.

Tight integration

WaterGEMS also brings the ability to easily view and manage timeseries data

to GIS, providing an intuitive means of viewing the changing conditions during

an extended period simulation from within the GIS environment. Since all of

the model data is already present in the GIS, the need to import the results

of each time step is eliminated. This extension of core GIS functionality illustrates

the tight integration between the modeling software and GIS.

An important feature of modeling software is the ability to calculate and view

multiple scenarios, and with WaterGEMS this functionality is available from

within GIS, allowing users to quickly switch between scenarios without changing

the active result files.

Using the geospatial analysis abilities of GIS, WaterGEMS enables the creation

of advanced, intelligent modeling capabilities such as automated demand allocation, and network skeletonization for water resource modeling.

True GIS integration with WaterGEMS eliminates the problems encountered when

using outdated techniques of data exchange that actually only provide compatibility.

It also facilitates the use of GIS in water resource modeling applications

by seamlessly running within the GIS itself and by leveraging the advantages

of GIS applications. Manual data transfer and connection are no longer necessary,

greatly improving efficiency and resulting in substantial savings both in time

and in effort.

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