Hydraulic modeling plays vital role in optimizing capital projects

(continued from page 27, August 2004 U.S. Water News)

August 2004

U.S. Water News Online

world, leading to an increase in its value and political importance, and a renewed focus on the efficiency and productivity of water utilities. This, in turn, is partly responsible for the growth in regulatory control and accountability (also driven by factors such as privatization and government legislation).

Further impetus has come from the new security environment the world now faces. Initiatives such as the US Homeland Security program place further demands on water operations, requiring the evaluation of options and the establishment of the most effective and robust operational policies.

Factors such as these demand that water utilities understand the operational behavior of their networks with utmost precision: to undertake modification works as cost effectively as possible; to minimize leakages; to respond to customer complaints in an informed and balanced way; and to anticipate disaster scenarios and plan responses. Hydraulic modeling as an operational decision-support tool

Since the day when modeling was used solely for simplified strategic evaluations, advances in modeling packages have enabled a very different sort of model to be built. The key characteristics of these models are:

  • A high level of detail -- very detailed models can be built because model build times and run times are constantly reducing. The value of detailed models, including all pipes, all valves, and all pumps for an area -- is that they can be used for operational decision making. The old strategic models had so many simplifications and assumptions that, useful as they were for high level optimization, they were not accurate at the operational level.
  • Easy links to all data sources -- models can be easily linked to GIS data, customer files, and other company and external data sources, ensuring good input data and ease of input.
  • Easy links to output files -- output to Word and Excel ensures that the results can be viewed and understood easily, extending the circle of use way beyond the model-builder to engineers with no specialist model knowledge.
  • Good housekeeping -- in the past modeling was not conducted to the standards of other IT projects, to their detriment. Good housekeeping of such issues as version control and audit trails broadens the user base of models.
  • Powerful simulation engines that permit Extended Period Simulation -- simple models running for short time periods and examining only peak conditions are of limited value. However, for a model to run accurately enough to support decision-making by operations management, the modeling package must have a simulation engine that runs big models quickly and reliably over extended periods way beyond the 24-hour effective limit of smaller packages.
  • Re-use of models -- models are no longer discarded automatically. Many companies keep them continuously updated, ready for application whenever a relevant issue requires it to be run.

The fact that models can be re-used has the benefit that they can be proven to a depth that can never be achieved with a throw-away model. Once a model has been used a few times for different purposes and been found solid, it will be trusted by operational staff to support their decision making. We list here just few of the possible applications that operational staff may address through models: Simulating pollution incidents

Water companies can use modeling to track the fate of any decaying or non-decaying substances, which might have been introduced either accidentally or intentionally, as they move through the distribution system. This understanding enables managers to assess the action that must be taken, identify the required response time and address the most critical areas first. The model can then be used to simulate mains flushing to facilitate the effective removal of the pollutant from the system, minimizing the disruption to normal supplies. Source blending

By tracing the percentage of water received at any point in the system from any of the sources to the system, water engineers can track the hydraulic boundary between the sources, assessing the areas where source blending occurs. This can lead to identifying required system modifications, often based on model results and spatial data such as customer complaints for taste and odor. Pumping systems optimization

Pumping costs are one of the most significant investments made annually by a water provider, yet very few assess their system operation, thereby failing to identify potential savings on OPEX.

Models can be used to optimize pump operation, maximising pumping during periods of cheaper electricity, and enabling operations staff to assess the efficiency of the existing pumps and any need for replacement/refurbishment and the potential reduction in running costs that might result. Chlorination A well-calibrated model with accurate demand allocation can be used to assess system chlorination requirements. The water provider can assess the concentration necessary at the water treatment works / source and determine the requirement for any additional chlorine boosters within the system.

Accurate assessment of water quality including chlorine residuals can help the water provider reduce incidents of customer illness and customer complaints. System storage optimization

Models can be used to optimize the operation of storage facilities, balancing supply and demand to allow steady flow from a source, which in turn benefits treatment works -- operators and bulk suppliers.

Optimizing the use of reservoirs and tanks prevents excessive retention times, improving water quality and reducing incidents such as bacterial growth in the reservoir or in the distribution system. A calibrated model can be used to ensure adequate reservoir turnover, and to test system re-zoning if required. Pressure management

A calibrated model can be used to assess the current system operating pressures and design pressure management schemes. This in turn can contribute to a reduction in system leakage, reduction in pressure related demand, reduction in burst incidents, and an extension in the life of the assets. Sediment modeling and mains flushing

Sedimentation analysis enables the assessment of areas in the system that may be prone to sedimentation. This information can be analyzed with mains material information and spatial data such as customer complaints of "dirty water" to pinpoint the reasons for the system problems and to optimize the use of mains flushing gangs to alleviate the problem.

A model can also simulate hydrant flow to develop an effective mains flushing program, and use property address data held with the network to list customers affected by the flushing program.

Conclusion

The argument above boils down to a simple summary. First, the need for efficient and effective operational management of water distribution has never been greater, and this need is likely to grow in the future. Second, modeling packages have never been better placed to contribute to meeting those needs. The final ingredient required is the human dimension. Operational engineers need to: • understand the opportunities modeling offers them for solving the issues they have to address • trust that the models they have access to -- pre-existing models that can probably be applied to their projects with little change -- represent the engineering reality of network operation, and not a mathematical abstract.

The first of these is a matter of the momentum of the industry -- the issue is being discussed more, the body of successful case studies grows, and the potential is clear to most operational engineers. However, that still leaves the issue of trust -- hearts rather than minds. To progress towards hydraulic modeling in operational management, operations staff need to talk with the experienced users of their company's models, understand the extent to which they are proven and reliable, and if the answers are positive, press ahead and reap the benefits.

For more information, please contact Paul Banfield, Sales Director, Wallingford Software Ltd., Howbery Park, Wallingford, Oxfordshire OX10 8BA, United Kingdom, +44 (0) 1491 824 777, fax: +44 (0) 1491 826 392, sales@wallingfordsoftware.com, http://www.wallingfordsoftware.com.

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