FLASHBACK TO 2002: Early decision-making by the Inter-Governmental Partnership was guided by a Backgrounder titled "The Water Balance Model: A Tool for Stormwater Source Control Modeling in a Watershed Context" (July 2002)

Note to Reader:

In July 2002, representatives of three levels of government (federal, provincial and local) convened at the inaugural Water Balance Model Partners Forum.

Hosted by Metro Vancouver, the defining outcome was the decision by the participants to form an Inter-Governmental Partnership with the responsibility to fund and proceed with Water Balance Model development.

This decision was informed by a Backgrounder document titled The Water Balance Model (WBM): A Tool for Stormwater Source Control Modeling in a Watershed Context. An extract is presented below.

A 2002 example of the type of output generated by a WBM analysis

A 2002 example of the type of output generated by a WBM analysis

Capture Rain Where It Falls

On July 17, 2002 the members of the Inter-Governmental Partnership decided to proceed with development of web-based a decision support tool for volume-based analysis of rain (and storm)water management strategies.

Named the Water Balance Model (WBM), the tool is versatile in meeting educational, watershed planning and site design needs and objectives.

The WBM provides an interactive means for local governments to integrate land use planning with stormwater management, and to evaluate the potential for developing or redeveloping communities that function hydrologically like naturally forested or vegetated systems.

The tool creates an understanding of how, and how well, stormwater source control strategies would be expected to achieve watershed protection and/or restoration objectives.

Application Possibilities

The WBM incorporates algorithms that simulate how runoff is generated at the site level, and has a wide range of application possibilities:

  • Design of volume-based stormwater controls
  • Site performance assessment
  • Evaluating opportunities for urban retrofits
  • Watershed management optimization
  • Analysis of global climate change impacts
  • Public education and outreach

A Perspective on Modeling

“The hydrologic modeling tools that are commonly used by stormwater practitioners originated in an era when ‘peak flow-based thinking’ dominated urban stormwater management and surface water modeling,” stated Dr. Dan Medina in 2002.

Dr. Medina was a US-based member of the Expert Panel that provided technical oversight during initial development (circa 2001) of the water balance approach for the dan-medina_2016_trimmed_120pMetro Vancouver region.

He then played a key advisory role during development of the calculation engine for “WBM 1.0” in the period 2002-2003.

“Therefore, not one of these models is suitable for modeling water balance volumes at the site level. This gap in modeling technology was the trigger for development of the WBM.”

“The power of the WBM is in the ‘engine’ that instantly, interactively, and transparently models hydrologic processes at the site level, including the processes that govern the movement of water through soil and vegetation.”

To Learn More:

Download Water Balance Model Backgrounder – August 2002 Update. This is a valuable historical document because it outlines the work plan for transforming the original Excel spreadsheet tool for use on a web-based platform.