Utility, Firm Meet Challenge of Creating 250,000-Pipe Model
Earth Tech has used InfoWorks WS from Wallingford Software to develop a record-breaking all-mains model of Miami-Dade’s water supply system ...
Earth Tech has used InfoWorks WS from Wallingford Software to develop a record-breaking all-mains model of Miami-Dade’s water supply system in order to achieve an accurate representation of the entire distribution process. The new dynamic model covers the entire 250,000-pipe network, as well as all the associated facilities.
Final calibration will be the next stage of the modeling process. It is believed that Miami-Dade will then have the largest water distribution model in use anywhere in the world – though it will not hold the record for long. InfoWorks WS is also being used to build an even larger model in Shanghai, China, that already has 400,000 pipes but is not yet fully calibrated.
The Miami-Date model includes everything from the smallest 1-inch supply pipes to major treatment works serving Miami-Dade County. The raw water supply is also being added to the model.
Representing something of this scale has meant overcoming a succession of challenges, such as finding out information about pipes laid a century ago. Calibration work and field research is now taking place to fine-tune the model in readiness for its use in a wide range of planning and operational tasks.
Modeling has been carried out in great detail. The task initially appeared daunting: the statistics are impressive. The model encompasses 5,600 miles of pipes, ranging from 1" to 120" in diameter. There are 218,000 nodes and 236,000 pipes in the model, as well as facilities including 49 treated-water pumps, 19 storage facilities and 98 raw-water wells.
The county’s original hydraulic model, built using another software system, was limited both in its coverage and its functionality, said Earth Tech senior hydrotechnical engineer Eppo Eerkes.
“It was only a single step simulation and couldn’t do extended-period modeling,” he said.
Only the trunk system was modeled, which served well for a planning-level analysis, but could not be used for detailed local distribution analysis.
“It also had a simplistic modeling of the pumping and storage facilities,” Eerkes said.
Only the main pressure zone was modeled. In addition to the smaller pipes that were not included, other exclusions were the raw water network and the well system.
Use of InfoWorks enables closer study of leakage in the area.
In contrast, the InfoWorks WS model includes carries out extended-period simulations. All facilities are now represented in detail, including reservoirs and every pump and pump curve. The model is designed to include the raw water systems as well as the interfaces between raw and treated water. All three pressure zones have been fully incorporated.
“One of the biggest challenges was that we had not finalized the software selection process before developing the model,” Eerkes said.
A structured approach was taken to the model developement.
InfoWorks was chosen by Miami-Dade County with the help of Earth Tech through a Modeling Software Selection Process. One of the reasons for selecting InfoWorks was its capabilities in terms of extended-period simulation on extremely large models. This was an essential feature for the new Miami-Dade model, as the engineers needed the ability to study how the system operates at different time steps and to explore aspects such as water quality and operations modeling.
The modeling process was divided in two streams -- distribution and facilities -- before being brought together into a single steady-state base hydraulic model. Aspects such as demand analysis, diurnal patterns and pump control rules were then taken into account to create the base extended-period simulation hydraulic model.
True elevations had to be determined to replace the single 1.5m value that had been assumed in earlier modeling.
The model draws on a wide range of inputs, including GIS data. Another key step was to develop a digital elevation model of the system. True elevations had to be determined to replace the single 1.5m value that had been assumed in earlier modeling.
The next stream of work involved developing the model for the wells, pumping and storage reservoirs.
“A lot of the locations were identified in the GIS but we had to add a lot more detail into the InfoWorks model itself,” Eerkes said.
An extensive process was carried out to develop the demand model. It involved allocating retail and wholesale demand, developing diurnal demand patterns and estimating unbilled water.
Once complete, the model will be used by the county for a host of purposes, including development approvals as many people choose to retire to the Miami area.
“The County wants to use the InfoWorks model to determine what capital works are required in order to allow the projects to be built,” Eerkes said.
It will also be used for evaluating potential storage locations and in pressure management, to reduce leakage. The information from the model enables demand to be broken down, showing the retail (residential, industrial, commercial and institutional) and wholesale supply.
“We can then find out what the unbilled volumes are,” he said.
Another role for model is in the monitoring of water quality parameters such as chlorine residuals or THMs. Further plans include using the model to help optimize operations in terms of aspects such as pumping.
“The County also wants to look more closely at its raw water system - nobody has ever modeled it before,” Eerkes said.
This article is based on a paper presented by Earth Tech senior hydrotechnical engineer Eppo Eerkes at the Wallingford Software International User Conference, 2007.