Computer modeling technology has advanced to the point that implementation of
modeling programs for small-scale potable water distribution systems such as
those at Air Force installations is now easily and effectively accomplished.
This paper summarizes Pacific Environmental Services' (PES) efforts to implement
a water distribution modeling software package at two U.S. Air Force Bases.
Model development was required to perform comprehensive hydraulic analyses of
each potable water distribution system. The model was also used to evaluate
specific operational scenarios, as well as evaluate and optimize several
construction projects under consideration. These efforts were part of a bigger
project to conduct a water vulnerability assessment that included evaluations of
the redundancy of facilities, the need for back-up treatment systems, the
ability of facilities to deliver adequate pressure for both normal use and fire
suppression, and manpower requirements.
The selected modeling package, WaterCAD, is a computer model capable of
predicting flowrates, pressures, and water quality conditions for differing
scenarios. The version of WaterCAD used in these studies runs within AutoCAD
drafting software. Model input data describing the geometry and characteristics
of all distribution system components were collected. Field-derived pipe
roughness factors were developed as a result of on-site flow testing.
Calibration was performed to ensure that the model accurately predicted
pressures, flowrates, and water quality characteristics measured through
field-testing. Once calibration was completed, several scenarios were postulated
and run to predict and/or analyze the impact of different operating conditions.
These scenarios included evaluating the distribution system's ability to provide
sufficient fire flows at key intersections, as well as sufficient flowrates and
pressures in other parts of the system during fire flow events. Several proposed
construction projects were evaluated to determine the best combination of piping
changes, operational modifications, and/or system upgrades to remedy known
low-pressure areas of the system. The model was also used to predict storage
tank levels at each Base in order to determine if operational changes could be
made to minimize stagnant water formation in each tank. Finally, the model was
linked to each Base's geographic information system (GIS) to allow for simple
updating of WaterCAD's input files, as needed in the future.
This paper is sponsored by the Air Force Institute for Environment, Safety, and
Occupational Health Risk Analysis at Brooks AFB, Texas.
Reprinted from Proceedings of 2002 AWWA Information Management & Technology
Conference, by permission. Copyright © 2002, American Water Works
Association."
Click here to
request a copy of this article in its entirety