Water Modeling: 7 Applications to Help Your Water System

In the last newsletter we introduced you to water modeling, which is a computer program used by engineers to model and analyze water distribution systems.  There are seven common uses for water modeling that are beneficial to cities and utilities to know you are getting the most out of the investment in your system:

  • Low Pressure or Fire Flow
  • Fire Flow Availability
  • System Reliability
  • Planning and Asset Management
  • Water Quality
  • Hydrant Flushing
  • Energy Use

These water modeling applications provide engineers, operators, and decision makers with the information needed to make wise decisions regarding planning, operations, and reliability of the distribution system. This quarter we will talk about three of them:

Low Pressure or Fire Flow

Troubleshooting known problem areas in a distribution system is often difficult when only using hydrant testing to understand how water flows through the system.  Water models simulate pressure and fire flow availability throughout a distribution system at any demand and operational condition desired and provide a glimpse into how water moves through the system, potential buildup in water mains, and other useful information.  Distribution system pressure is ideally between 60 and 80 psi.  A water model can be used to identify areas of the distribution system that do not fall within the ideal operating pressure range. That information can be helpful in planning and prioritizing capital improvements to improve service and pressure to users.

Hydrant Installation. New fire hydrant installation in an existing residential neighborhood. System improvements were modeled with a water model.

Fire Flow Availability

Federal and state laws do not require sizing the water distribution system components for fire protection; however, providing a water distribution system that can deliver adequate fire protection is a local decision to reduce the risk for loss of life and property.  Insurance providers determine the flow and volume necessary to minimize damages based on occupancy, building materials, area, volume, and separation of individual structures.  The Insurance Services Office (ISO) of Iowa and the America Water Works Association (AWWA) recommend fire flow ranges for the listed general building classifications listed in Table 1. 

Table 1 – ISO and AWWA Recommended Fire Flow Availability  

Zoning Fire Flow Available (gpm)
Residential 500 to 1,000
Commercial 1,500 to 2,500
Industrial/Institutional 3,000 to 12,000

Available fire flow is the maximum amount of flow available from a hydrant while maintaining a minimum pressure in the distribution system, which is commonly 20 psi. Typically, hydrant testing is completed during business hours, when distribution system demand is not at its peak.  A water model can simulate fire flow availability during peak water demand, which only occurs on a few days each year and early in the morning or late in the evening, outside of business hours when residents are home and water use is at its daily peak.

System Reliability

System reliability is important to ensure uninterrupted water service to customers even when water main breaks, repairs, or system maintenance occur.  This is especially important for communities who have industrial, commercial, and healthcare centers that require a constant water supply.  A water model can be used to identify areas of a distribution system that are at risk of impacting large service areas if one of these events occur.  Once the critical areas of the distribution system are identified, then City decision makers can plan for improvements to provide additional water supply connections to at-risk areas or install the valves required to adequately isolate areas of the distribution system.

Water Main Improvements. Installation of a new water main to improve system reliability where existing water main experienced frequent breaks.

Summary

When making decisions regarding your water system, you want to know that you are getting the most value for your investment.  Water modeling, in conjunction with field testing, provides a valuable picture of the condition of your water system and can be used as a tool to improve operations.

FOX Engineering is an environmental engineering firm based in Ames, Iowa. We specialize in water and wastewater solutions for our diverse municipal and industrial clients. Our work varies in size and scope and can be found throughout the Midwest and beyond.