Rainwater Management in the 21st Century: Water Balance Model can help create a vision of the future watershed


The Water Balance Model is Unique

Developed as an extension of the Stormwater Planning: A Guidebook for British Columbia, the Water Balance Model (WBM) bridges planning and engineering; links development sites to the stream and watershed; and enables science-based performance targets to be established. It is a scenario comparison and decision support tool. The ‘WBM powered by QUALHYMO’ differs from other drainage modelling tools in three fundamental ways: 

  • it is web-based;
  • development is driven by the community of users; and 
  • it can help create a vision of the future watershed.

All three are powerful in their own rights. There is no other comparable web-based tool,” states Dr. Charles Rowney, WBM Scientific Authority and creator of the QUALHYMO calculation engine. The WBM demonstrates how to achieve a lighter ‘water footprint’. This helps planners and designers wrap their minds around how to implement ‘design with nature’ solutions on-the-ground. The stream health methodology embedded in the WBM enables a watershed target to be established. It also enables the user to assess how to meet the watershed target at the site scale.

“A key message is that the WBM is a unique ‘scenario comparison tool’. Because there is no restriction on the scenarios, this allows users to create an understanding of the past and present and compare it to many possible futures. This capability allows communities to assess how watersheds can be altered, for good or bad. Then they can create a vision of where they would like to go, and how the watersheds can meet their vision,” adds Jim Dumont,  WBM Engineering Applications Authority.



The WBM is the shared legacy of a team of senior practitioners. The tool is the outcome of a building block process. For more information on the history of this unique tool, click on Water Balance Model powered by QUALHYMO: A Team Effort.


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