Water and Sewer System Modeling: What Are the Benefits of Hydraulic Models?

Polk County and Central Florida are growing at an unprecedented rate with no signs of slowing down.  Due to this growth, local municipalities are seeing a need to allocate large amounts of capital toward sewer and water system infrastructure improvements. During this time, when budgets are tight, municipalities are understandably questioning the need to create and maintain hydraulic models.

This post aims to answer the frequently asked question…

In short, hydraulic modeling involves using computer software to simulate the flow of fluid within piping systems. In potable water (distribution) systems, this involves modeling the pumping stations from the water treatment plants and distribution to the users within the network. In sewer (collection) systems, this involves modeling the collection of sewage from the users and transportation to the wastewater treatment plants.

A hydraulic model assists in both day-to-day operations and future planning in water and sewer systems.

For operations, a hydraulic model can be used to identify potential areas of concern, zones of inefficiency, how the system behaves under a variety of scenarios, and how it reacts to operational changes. Models are easily updated and maintained to provide a real-time snapshot of the system.

For instance, water system models can be used in conjunction with field data to quantify and identify sources of water loss or provide estimates of available flow for fire protection systems. Sewer system models can be used to identify locations with high amounts of stormwater inflow and infiltration.

For planning, a model can identify areas currently limited in capacity and can predict which areas may become overloaded in the near future. This predictiveness allows for the design and construction of improvements prior to issues arising. When a new development or industry wishes to connect to the water and/or sewer system, the associated models can determine capacity and aid in any cost-sharing between the developer and municipality.

In addition, hydraulic models are integral to the master planning process. It is used as a tool to estimate how the system will function 5, 10, or even 20 years into the future. This information is crucial in allowing the municipality to rank needs within their system to best decide how to allocate funds, as well as helping to provide documentation of need when additional funds from grants and other programs are necessary. ^{1 | 2}

Smaller municipalities may have progressed for some time without a model of their system. When a system is smaller, it is easier to manually calculate the impact new development and industries will have on the distribution and collection systems. As they grow, it becomes increasingly taxing to monitor these impacts.

For example, the City of Lakeland has 180+ sewage pump stations, 330+ miles of gravity sewer pipelines, and 140+ miles of force mains. A new development in Lakeland may not cause negative impacts on the nearby infrastructure but can instead cause impacts miles down the line. For this reason, it is very important that growing municipalities create and maintain a model of their system. ³

Chastain-Skillman, Inc. was contracted to create a hydraulic water model for a local municipality. The calibration of the model involved flow testing fire hydrants and comparing the available fire flows measured in the field with what was simulated by the model.

In one testing location, on a looped system, we measured a rapid drop in pressure in the field, but the model suggested we should have had significantly more pressure in the line. This type of pressure drop is normally an indication of a potentially closed valve in the water main. In conversations with the municipality, they assured us they didn’t have any valves closed in the system and were hesitant to search for closed valves.

The process of searching can take a while, as there are many valves on the loop, and city operators are normally very busy. However, the model was able to pinpoint a location it anticipated being closed.

Sure enough, when we checked the area with an operator, the first valve we tested was closed. Opening the valve made a significant impact on the available water, water pressure, and most importantly the available fire protection for a large portion of the city (see figures below).

Without the information from the water model, the issue may have gone unidentified until a major incident occurred. Once an incident occurred, the time needed to inspect the water main to identify the cause and location of the source of the issue could have taken many weeks.

Our experience at Chastain-Skillman, Inc. has shown us the importance of modeling the various pipe networks controlled and operated by growing municipalities, no matter the size.  Not only does this information aid in day-to-day operations, but it allows municipalities to better identify and address the current and present needs of their growing systems.

The ability to use hydraulic modeling to review pipe networks helps to mitigate issues before they arise, prepare for future growth, ensure funding is directed to the most important areas of the system, and aid in the ability to show a need for procurement of external funding.

Chastain-Skillman’s team of local experts has extensive experience with hydraulic models for potable water and sewer systems. Whether it’s providing upgrades to an existing system or planning for future enhancements, our team of engineers can help you determine the next step in improving your infrastructure upgrades. Contact our team today to discuss if investing in hydraulic modeling is right for you and your organization.

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