Sensor Data Helps Calibrate Water Models
Thomas M. Walski, Ph.D., P.E., D.WRE, F. ASCE, is Bentley Systems senior product manager for Water and Sewer Products. Walski has been intimately involved with the modeling of water networks for decades, and has worked with Bentley Systems to introduce seminal hydraulic modeling tools such as WaterGEMS and WaterCAD. He recently discussed the impact of modeling and sensing on modern water systems with Informed Infrastructure.
Informed Infrastructure: Tom, what’s your role at Bentley Systems, and why are you interested in sensing in particular?
Walski: My role is to define where our software is going, and to anticipate and address user needs. Sensing comes into that because SCADA [supervisory control and data acquisition] data is an excellent way to calibrate models so that they become truly useful for the design and operation of particular networks. A lot of our R&D is devoted to this, and there’s a lot of opportunity for applications, especially on the operations side of water suppliers—this is where we’re moving with our modeling. Our SCADAConnect module, for example, creates easy workflows for bringing SCADA data into models. And once calibrated with real data, the models can be used to design improvements, detect problems, and run ‘what if’ studies that give useful results.
In terms of temporal resolution, SCADA is tremendous. You may only have continually updated data at relatively few points in the system, but a model allows a user to ‘fill in’ the space between sensors. I’m sure in a few decades we’ll see more densely sensored networks, but what’s common now is usually more than sufficient to make predictions about whole networks.
One of our initiatives is to get more folks on the operations side of water systems to see that modeling is a tool for them, and not just for engineers and planners. We think that designers and operators both benefit when they share data. In fact, some of our favorite people are those whom come to engineering or planning after working as operators—they see the value of both sides, and can see the value of leveraging information for multiple benefits.
Informed Infrastructure: What role do water networks play in improving water availability in impoverished regions? What should relative investment be, for example, compared to other forms of development?
Walski: The big push in less developed regions is to move to 24/7 water supply, as opposed to intermittent water supplies. That’s a big, beneficial transition; when water is on 24/7, for example, it’s cleaner because there’s less infiltration, and it’s easier to detect leaks and manage pressure. It’s also better for people, of course.
Now, if it’s a question of supply that’s preventing 24/7, then network management or modeling doesn’t have a big role to play—first, work on supply. But if it’s leaks, non-revenue water, or pressure issues that are preventing 24/7 supply, a reasonable investment in sensing and modeling can help a lot.
Informed Infrastructure: Is there any ‘low hanging fruit’ in this arena? That is, are there relatively cheap investments that will have high positive impacts?
Walski: One thing that occurs to me are DMAs [district metered areas] which have become a very useful tool for water management. When large networks are broken up into at least a few separate parts, and usage is monitored in these areas, managers can really learn a lot. Just basic flowmeters, read manually, can make a big difference. Tying them into SCADA makes them even better. Most obviously, it’s much easier to get a handle on leaks and water loss. When you have a whole system to investigate, it can be overwhelming; narrowing it down to a particular area really helps. DMAs enable managers to get a handle on where water is going and to be proactive or, at least, to react more quickly.
We’ve worked with United Utilities in the UK to verify our Darwin Leak Calibrator tool in our WaterGEMS model. They were able to pinpoint areas where leaks were likely. We’ve used their field data as benchmarks to test our models and tools.
Informed Infrastructure: Specifically, how can better network management improve water availability?
Walski: When designers and managers use reality-informed models to get a good understanding of the system, they start to get a sense of where water ‘ought’ to be going. And they can compare modeled predictions to field data to detect problems; if pressure in a DMA is lower than predicted, for example, they can investigate—it may be something as simple as valves that should be closed or opened.
Pressure management can be very complex. It’s obvious that lower pressures cause less leakage, but just lowering pressure without a plan can negatively affect the whole system. Informed hydraulic analysis is a good way to create pressure management plans. And again, DMAs are a big help.
Of course, a model is only as good as the data used to create it. If a system is poorly mapped, then basic collection of spatial data and mapping is the first step, and comes before hydraulic analysis.
Informed Infrastructure: Can sophisticated network management improve performance of relatively unsophisticated systems? If so, what are some strategies for implementing better management?
Walski: I’d say some basic requirements need to be met before hydraulic analysis is genuinely useful. I mentioned mapping and inventory management. There also needs to be some basic sensing ability in the system, even if it’s just a few flowmeters read every couple of days. And some version of DMAs can be useful. I’d say there also has to be the will to do simple things like finding and fixing leaks. A district has to make a commitment to good practices before anything else will work.