Hydraulic Model Calibration: Detecting the Hidden Clues in Your Water System

Accurate hydraulic modelling goes far beyond just simulating water flow: it's about truly understanding the operations of your water distribution system. When done right, model calibration doesn't just align simulated and real-world performance, it uncovers hidden issues that could be quietly affecting your system's efficiency.

One of the most common yet often overlooked discoveries during model calibration is the presence of open boundary valves or incorrect pressure zone configurations. These subtle operational misalignments can have significant impacts.

Case in Point: City of New Westminster, BC

In my presentation to the British Columbia Water and Wastewater Association (BCWWA) back in May 2017, I shared a revealing case study. The City of New Westminster had long struggled to fill a key storage tank during the night, exactly when water demand is supposed to be at its lowest. The culprit? An open boundary valve was allowing water to leak into a lower pressure zone, undermining system performance.

This kind of discovery is not unique. In fact, identifying unexpected valve positions or pressure zone shifts is one of the most valuable outcomes of a thorough calibration process.

A Quick Technique to Spot Potential Issues

Want to test your own system for possible open valves? Here's a practical, quick method using your hydraulic model:

• Select a Scenario — Use the Maximum Day Demand scenario if possible.
• Run the Model — Color-code junctions by pressure head (meters).
• Overlay the Zone Boundaries — Add these as a background layer.
• Inspect the Boundaries — Look for areas where pressure heads blend instead of showing the typical 20–30 meter difference. Minimal difference might indicate an open valve or a misrepresented boundary.

Another Red Flag: Trouble calibrating just one or two hydrant flow tests, especially if others match well, may signal a mismatched pressure zone or valve setting. The pressure curve itself can even help determine which zone the hydrant actually belongs to.