Hydraulic and chemical models of water distribution systems can be interfaced with on-line sensors to provide a highly accurate and up-to-the-minute description of system operation. Such models can be used for real-time monitoring and diagnostics. They can also be used to improve system operation, evaluate replacement or system expansion options, solve pressure/flow problems, and solve water quality problems. The installation of a real-time sensor-enabled water distribution system model at an Army installation will be described. Concepts for the use of dynamic utility system models as part of an overall virtual installation planning and operations tool will be discussed.
The U. S. Army is investigating the use of sensor-enabled computer-based models to help improve the operation of potable water distribution systems at its installations. Just as in the private sector, facilities engineers on Army installations strive to meet customer demands for potable water in a reliable and safe manner. The water distribution system must fully support a diverse variety of missions including the rapid preparation and deployment of equipment and troops. System security and emergency preparedness are also critical to protect the lives and safety of soldiers and their families. The water system operator must be ready to detect and quickly respond to new conditions or situations as they arise.
We often rely on the experience of the water system operator and engineer to solve problems or respond to new situations. Many experienced system operators sense how their water system operates, and intuitively predict how it will respond in various situations. Experience allows them to recognize when something is wrong with the system. The underlying obstacles to this approach arise when an unfamiliar or time-critical situation occurs. Without the understanding that is given by a calibrated and detailed system model, the operator must blindly execute a solution. Additionally, there are problems related to transfer or retirement of system experts prior to adequate training of a new system operator.
Computer-based models provide site-specific, clear, and detailed insight into the operation of a water distribution system. They can be used to ensure adequate water supply, investigate possible solutions to problems, aid in emergency response, or optimize system performance. They can also be used to capture the institutional knowledge that tends to be lost when an experienced operator retires.
There are several general types of water distribution system models. These are illustrated in Figure 1 and are pictured in order from least accurate and reliable on the left, to most accurate and reliable on the right. The steady state (static) computer model calculates system hydraulic parameters such as flow rate and pressure at a given moment in time. This type of model can be useful for the analysis of situations that do not involve timevarying behavior. The off-line dynamic model calculates system hydraulic parameters (just like the static model), but it takes into account the system?s time-dependant behavior. For example, consumer demands are allowed to vary with time; valves can be opened and closed; pumps will operate according to a specified set of rules; and water levels in the storage tanks will vary. Instead of representing the water system?s behavior at a given moment in time, the dynamic model typically simulates its expected behavior over a period of hours or days. Some dynamic models include the ability to simulate water chemistry at each location in the system as it varies with time.
It is often difficult to calibrate off-line models such that they accurately