Water Systems Distribution Modeling

Charter Oak conducts hydraulic modeling of municipal water supply and distribution systems.  Our models include typical water system components including water supply sources, storage tanks, booster pumps, piping, pressure reducing and sustaining valves.  System evaluations consider steady state and time varying conditions of water supply and demands in evaluating the performance and adequacy of water system components.

The WaterCAD model by Haestad Methods is a powerful, flexible and widely accepted water system model, and is Charter Oak’s model of choice.  WaterCAD is a state-of-the-art model, and can import or export mapping to and from the Softdesk AutoCAD environment.  Alternatively, files can be imported or exported in DXF format for use with many other computer mapping packages.

Typically, our approach to preparing a water distribution system model consists of four components, which are described briefly below:

  • Data collection and input;
  • Model calibration;
  • Model verification; and,
  • Predictive modeling.

Data Collection and Input

Available mapping and information are obtained and used to prepare a base map within the AutoCAD mapping environment.  In general, pipe sizes 4 inches and larger are considered, unless it is determined that modeling smaller pipe sizes will affect the performance and accuracy of the model.

This AutoCAD base map, following review and approval by water authority staff, is imported to the WaterCAD modeling program.  The WaterCAD base map will include piping layouts and sizes, water storage tanks, pressure reducing/sustaining valves, water supply wells, booster stations, fire pump booster stations, fire hydrants, system demands and other known distribution system operating parameters

Model Calibration

A steady state (water demand not changing over time) condition is assumed to calibrate the computer model.  Information including previous field tests, the review of reports and discussions with persons knowledgeable about the water system, fire flow tests, and new static and residual pressure tests performed for purposes of a project are used to calibrate the model.  Typically, model input is reviewed and adjusted as necessary to achieve calibration within 90% accuracy.

Model Verification

The verification step assures the water authority that the model is useful beyond the specific model nodes or locations in the water system.  In this process, pressure and flow readings at hydrants in locations other than those used in calibrating the model are obtained.  The measured values should be predicted by the model with reasonable accuracy, hopefully within 90% of the actual values.

Predictive Modeling and System Evaluation

Following successful calibration and verification, the distribution system model is used for predictive analysis of various operational conditions including fire flow conditions, average daily and maximum daily water demands, and future system connections and alterations.  The system evaluations provide valuable information throughout the distribution system, including water flow rate, velocity and pressure, and flow direction.

Based on the outcome of the water distribution system evaluation, Charter Oak can assist the water authority with identifying problematic areas within the system.  Additional predictive modeling is performed if necessary, and system improvements are recommend to address those problematic areas.

Issuance of Reports

Following completion of modeling and providing recommendations for improvements, we typically issue copies of a preliminary report to the water authority for review.  The report describes the methodology utilized, investigations performed, the data used to prepare the model, and proposed recommendations and cost estimates if applicable.  Charter Oak then meets with water authority staff to review the report, and following modifications and final acceptance, Charter Oak issues copies of the final report.