Rainwater Management in the 21st Century: “Focus Drainage Modelling on Solutions”, says Dr. Charles Rowney



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From Theory to Interpretation

The graphic shown above is a synthesis that comprises eleven steps that cascade down from a theory to interpretation of results. Dr. Charles Rowney, Engineering Applications Authority for the “Water Balance Model powered by QUALHYMO”, has coined this mind-map as the Uncertainty Cascade:

  1. Theory
  2. Conceptual Model
  3. Mathematical Model
  4. Solution Algorithm
  5. Code
  6. Adjusted Algorithm
  7. Executable
  8. Site Representation
  9. Calibration
  10. Case Representation
  11. Interpretation

“There is a preoccupation with theory, but the heavy lifting takes place in the last four steps. We need to keep our focus on SOLUTIONS on the ground,” emphasizes Dr. Rowney.


From Theory to Interpretation

“We start with a theory, we develop a conceptual model of that theory and how things work. Next, we come up with a mathematical model that describes that concept, and we create a solution algorithm. We write some computer code, we adjust that because the code never really does what we want it to, and we come up with an executable.”

“Then we start to represent the site and start putting all our data together. We calibrate and adjust our model with the data. Then we start to think about how we will look at our future case. And finally we start to interpret our results.”

“Much of the discussion and arguments are about the theory and model. You will hear these kinds of statements: I have a model that does this or does that; I can do a pipe this big or that big; I can do this kind of thing, I can do that kind of thing. Yet the heavy lifting is at the other end.”

“The real problems and solutions come together when you look at the site and the data you have to represent what you have. How do you compare the future condition that is very undefined with a calibrated tool that is very well defined? There is much that we do that has a place and purpose, BUT sometimes what we do is questionable.”


Focus on Solutions

“We have learned that we really need to look at things from the point of view of the solution. As we have been working on the WBM, we have been orienting it to THE SOLUTION. We are keeping it as simple as possible, but no simpler. The tool has to be consistent, inexpensive, and workable with limited data. It has to fit the local context, and it has to evolve as we learn.

“What is it that we really want to solve? Where are we driving this?  We have ample horsepower to pick just about any theory we want and put it inside the WBM. But what we really need to focus on is: what are the solutions that are really necessary. Once we have figured out the solution that we need, we need to come up with tools that do that and no more and no less.”

“An outcome that we are pushing for is the ability to interpret results, and the ability to represent the cases that we are actually trying to solve.”


Bridge between Scales of Need

“There are two levels of thinking. At one level is the broad scale of planning where we look at how and where we might wish to go tomorrow – for example, how should we view the watershed and what might we do to protect receiving waters. And at the other level is the need to eventually put something on or in the ground.”

“We need to bridge those two kinds of needs. With the WBM, we have a tool on a platform that is designed to do just that. As we go forward with model development, we need to know more and more about that polarity. At one end, it is about where are we going to take this tool. At the other end, lot by lot by lot, it is about how we put things in the ground to ensure they work.”

“What we have learned is that we really need to take a look at this from the point of view of the solution. As we have been working on the WBM, we only go as complicated as is necessary. We strive to make the tool as simple as possible, but no simpler. It has to be consistent, cheap and workable with limited data. It has to fit the local context; and it has to evolve because we are not at the end point today. The WBM will continue to grow and adapt over time,” concluded Dr. Rowney. 



The foregoing is extracted from a guidance document released by the Partnership for Water Sustainability in November 2011. To download a copy, click on Primer on Urban Watershed Modelling to Inform Local Government Decision Processes


Dr. Charles Rowney at the 2011 Water Balance Model Partners Forum