Hydraulic Modeling for Water Systems

What is Hydraulic Modeling?

• Hydraulic modeling is the use of a computer program to simulate the flow of water through pipes, pumps, reservoirs, valves, and other components of a water system. Once the hydraulic model is prepared it can output data such as pressure, tank level, pipe head loss, and various other items that are vital to the evaluation, operation, and maintenance of a water system.

How is a Hydraulic Model Prepared?

• The steps for preparing a hydraulic model consist of data gathering, system mapping, model setup, model calibration, evaluating results, and reporting.
• Data Gathering
  • The engineer will begin by obtaining any available information for the water system to be modeled that would result in greater model accuracy.
  • Data that will need to be gathered for the water system may consist of:
    • Existing system GIS or CAD maps
    • Waterline location and sizes, fittings, and tank materials/sizes
    • Topography/elevation data
    • Pump capacities
    • Valves and other system controls
    • SCADA settings (if any)
  • System Mapping
    • Once the system data has been gathered, preparation of the model can begin. The next step to mapping the water system in the hydraulic model software is adding in pipes, valves, tanks, reservoirs, and any other water system components.
    • The most current hydraulic modeling software is GIS based. The layout of the water system and its components can be either entered manually or imported as GIS shapefile data from existing water system maps. The shapefile data can then be converted to pipes through tools in the modeling software.
    • This step also includes adding in component details & dimensional information such as pipe sizes, roughness coefficients, tank sizes, materials, etc.
  • Model Setup
    • Once the water system components have been added into the hydraulic model, the hydraulic components of the system can be defined, such as water demands, valve settings, tank/reservoir settings, control settings, and any SCADA controls.
    • At this point, demand scenarios will also be created to model different flow variations anticipated throughout the system over a desired amount of time.
    • For a typical water system, the following 3 separate demand scenarios will be created.
      • Maximum Daily Demand Scenario
        • This demand scenario will represent the system when the water use is the highest such as in the mornings when people are getting ready for work or in the evening when people are returning home from work and are using more water.
        • This scenario is typically modeled using a demand of 1.5 gallons per minute per connection.
      • Average Daily Demand Scenario
        • This scenario will represent the system operating under normal day-to-day operations.
        • This demand scenario is typically modeled using the TCEQ minimum capacity requirement of 0.6 gallons per minute per connection.
      • Static Demand Scenario
        • This scenario will represent the system’s maximum pressures anticipated when there is little to no demand on the system.
        • This scenario will be used to ensure the water system components are capable of handling pressure surges.
      • A fire flow demand scenario may also be added into the system dependent on if the water system has fire flow requirements.
    • The above demands may vary dependent on if the water system has an approved alternative capacity requirement from the TCEQ lowering the average daily demand per connection.
  • Model Calibration
    • Once all modeling parameters have been input the model simulation can be run to generate results.  But before the model is deemed complete, and to increase the accuracy of the results, the model should be calibrated.
    • Model calibration can be completed in a number of ways. The most typical will involve sitting with the water system operator and running through the model to ensure the simulation results are a good representation of how the water system is actually operating.
    • A discrepancy in the simulated results will warrant revisions to the model such as updating pipe sizes, pipe connections, or operational settings until the model yields more accurate results.
  • Evaluation
  • Once the model is running correctly, the output can be analyzed in order to evaluate the system.
  • The output analysis can then be used to highlight deficiencies or operational vulnerabilities in the system, identify system capacity issues at specific locations, or evaluate the impact of planned expansion.
  • Reporting
    • Once the model calibration step is completed and the model is outputting expected values then reports may be generated showing the model results under the varying flow conditions.
    • The report itself will vary depending on the final deliverable expected by the client, but it typically involves creating maps that show key items such as pipe flow, pressures, pipe velocities, and frictional head losses.

Importance of Hydraulic Modeling

• As stated previously, hydraulic modeling is vital to the evaluation, operation, and maintenance of a water system. Here are some specific reasons why hydraulic modeling for a water system is important:
  • System Design and Optimization
    • Hydraulic models aid the design parameters for infrastructure improvements to ensure that current and future needs can be met.
    • The engineer may recommend ways to optimize the water system such as changes to setpoints on valves, tanks, and pumps.
  • Leak Detection and Repair
    • The hydraulic model can aid in leak detection by comparing simulated vs actual flow rates and pressures.
  • Emergency Preparedness
    • Hydraulic models can simulate emergency conditions such as pipe bursts, pump breakdowns, and pump station power failures. The emergency scenario results can aid in planning for emergency responses such as backup line routes or isolating the parts of the system that may be affected by these emergencies to reduce the impact on the overall system.
  • Water Quality Management
    • Hydraulic models may be used to track water quality and water age throughout the network identifying areas that may be affected by these issues such as dead-end lines with little to no water use.
  • Regulatory Compliance
    • The TCEQ regulates public water systems and establishes minimum supply, quality, and capacity requirements. A hydraulic model could greatly benefit the system owner to ensure their system can comply within these requirements.
  • Planning for Growth
    • Cities around the State of Texas are experiencing substantial growth and hydraulic models can be used to plan for this growth and to ensure the system can provide safe and clean drinking water to its current and future connections.

How can JACOB|MARTIN Help?

• Throughout our 75 years of existence, JACOB | MARTIN has prepared numerous hydraulic models for water entities throughout the state of Texas. We keep an up-to-date hydraulic model for our current clients to ensure a high level of service and help solve issues as they arise.
• We would be more than happy to help a municipality or WSC prepare a new or optimize an existing hydraulic model.
• For more information, contact Derek Turner, P.E., Senior Principal at (817) 594-9880, or your local JACOB | MARTIN representative.