Hydraulic Models for Drinking Water Systems
Hydraulic models are an integral tool in the design, operation, and optimization of drinking water systems around the world. Generally, hydraulic models predict the results within a water system during various scenarios. Once the hydraulic model is successfully calibrated (predicted results match real world results), numerous scenarios and configurations of the water system can be simulated with results developed in real time.
Design
The most common use of a hydraulic model is in the design of water system components. Most drinking water systems are configured with “looped” water distribution system piping. This means that the path water takes from a source to an end point flows across two or more paths or pipes. Flow and pressure calculations can be done by hand. However, the calculations are a time-consuming process that quickly becomes an unjustifiable cost.
Using computer hydraulic models, numerous configurations and changes to a water distribution system can be simulated and analyzed in relatively short order with a significant reduction in costs. If the task is to simply size a new water main to service future development, numerous simulations with differing pipe sizes can be completed in minutes. These results can be analyzed, and the size of the proposed water main can be selected.
Certainly, more complex tasks can be accomplished through computer modeling, such as fire flow analysis, pump sizing and selection, and pressure reducing just to name a few. With the ease of using computer modeling, your imagination as an owner, operator, and engineer can be set free. Ideas that may seem unrealistic may turn out to be a valid solution. On the other hand, those reasonable assumptions may not produce the expected results.
Operations
Hydraulic computer models can also be a vital tool in the operation and maintenance of water systems. Once calibrated, pressure results throughout a distribution system can be compared to real world pressures. As these real-world pressures change over time, it may be an indication that system components may be failing. For instance, operators may notice a pressure drop during a routine flushing operation. Surrounding pressures are compared to the predicted computer model results and the low-pressure area and those pipes serving the area can be identified. This narrows, and in some cases may identify, the component(s) of the system that are leaking and causing the pressure loss.
Optimization
Another aspect of hydraulic modeling is for optimizing water system components, such as pumps and pressure reducing valve settings. Again, numerous situations can be simulated with the results analyzed in relatively short order. This allows for optimized system settings to be identified without actually changing real components. As some may attest, changes in operation and settings of real water system components can have unintended and detrimental impacts to water lines and customers. The thought of creating these detrimental impacts within a water system keeps most operators from changing existing settings. Hydraulic modeling takes the experimentation uncertainly out of the equation.
With the advent of GIS mapping for managing water system components and information, so too has the need to integrate hydraulic modeling output. GIS components and hydraulic model components can be joined to make modeling data accessible. For instance, modeled fire flow results can be assigned to GIS-located fire hydrants for the use of Fire or Insurance Officials. The results are used in establishing insurance rates for a community. Actual water supplied and water usage data can be inserted into GIS maps and shared with hydraulic model junctions to keep predicted water system results current.
Of course, there is a cost in creating a hydraulic computer model for a water distribution system, but it can certainly be offset through the increased efficiency in completing a multitude of tasks. From sizing water system components to optimizing existing operations, a soundly created and well-maintained hydraulic model is an irreplaceable tool for an owner and engineer.
Part 2 - How Water Models Are Created
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