Rainwater Management in a Watershed Sustainability Context – What’s the Goal?


Note to Reader:

In its November-December 2010 issue, Stormwater magazine launched the Green Infrastructure & Community Design Series. Articles in the series have been contributed by members of the Rainwater-in-Context Initiative. Formed in 2010, the initiative works to institute rainwater management practices that strengthen and fully complement “new urbanism” at all scales.

The last article in the series was co-authored by Kim Stephens and Jim Dumont,  Canadian contributors to the Rainwater-in-Context Initiative. The article is a compendium of the perspectives of those leading change in British Columbia. The article elaborates on how science-based understanding has informed the process for moving from awareness to action in British Columbia.

The following is an extract from the article. To download the complete article, click on Rainwater Management in a Watershed Context – What’s the Goal?

The View from British Columbia

“Looking back, 2008 was a defining year for green infrastructure on Canada’s west coast. The government of British Columbia put in place a policy framework that is a ‘call to action’ on the part of local governments. This call to action is underpinned by the notion of shared responsibility – that is, everyone needs to understand and care about THE GOAL. If all the players know their role in relation to the goal, then together we can create the future that we all want,” states Kim Stephens, Executive Director of the Partnership for Water Sustainability in BC.

“A key message is this: A science-based understanding of the rainfall-runoff process is the foundation for designing with nature and implementing green infrastructure that is truly effective in protecting watershed and stream health.”

Create a Vision of the Desired Watershed Condition

British Columbia’s Water Balance Model (www.waterbalance.ca) bridges planning and engineering; links development sites to the stream and watershed; and enables science-based performance targets to be established. This unique scenario comparison and decision support tool 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.

“Developed as an extension of Stormwater Planning: A Guidebook for British Columbia, released in 2002, the Water Balance Modeldemonstrates 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 Water Balance Model enables a watershed target to be established. It also enables the user to assess how to meet the watershed target at the site scale,” explains Ted van der Gulik, Senior Engineer in the BC Ministry of Agriculture and Chair of the Water Balance Model Partnership.

“A key message is that the Water Balance Model is a ‘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.”

Mimic the Water Balance

Water reaches a stream via three pathways: surface runoff, shallow groundwater (interflow), and deep groundwater. Scroll down to image below.

“With release of the Guidebook in 2002, BC was the first provincial or state government in North America to adopt the Water Balance Methodology. The methodology enables local governments to establish performance targets for land use. A design objective is to maintain the proportion of rainwater entering the stream via each pathway,” states Kim Stephens. He was project manager and principal author of Stormwater Planning: A Guidebook for British Columbia.

Focus on Protecting and Restoring Stream Habitat

“The approach we have taken in British Columbia differs from that of the United States EPA due to the nature of the root problems being solved,” continues Jim Dumont, Engineering Applications Authority for the Water Balance Model Partnership. ”The critical issue in British Columbia is the damage and loss of habitat caused by development and Jim dumont (120p)erosion of the headwater streams. The focus is in direct response to Canada’s Fisheries Act that prohibits damage of fish habitat.”

“EPA has focussed upon water quality in the main stems and coastal waters and seeks to restore the resources of those waters through the goals and objectives of the Clean Water Act.”

“Perhaps when the EPA focus shifts from water quality to include habitat loss the lessons learned in British Columbia can be reviewed and incorporated into the policies and objectives of the EPA.”

To Learn More:

To download the complete article, click on Rainwater Management in a Watershed Context – What’s the Goal?

Integrated Strategy for Managing the Rainfall Spectrum & Mimicking the Water Balance