Application of "Whole Systems Approach" – Watershed protection starts with an understanding of how water gets to a stream….
Water Balance Methodology Integrates Sites with the Watershed, Streams and Groundwater Aquifer
Washington State research informed the early implementation of British Columbia’s Fish Protection Act (1997), the first legislation of its kind in Canada. In the mid-1990s, the pioneer work of Dr. Richard Horner and Dr. Chris May (University of Washington, Seattle) was transformational. Their findings resulted in a hydrology-based framework for protecting watershed health. The framework provided a starting point for applying science-based understanding to reinvent drainage engineering practice, commencing with release of Stormwater Planning: A Guidebook for British Columbia in 2002.
Mitigate ‘Changes in Hydrology’
“Watershed protection starts with an understanding of how water gets to a stream from individual sites, how long it takes, and whether there are impacts along the way. The work of Richard Horner and Chris May was a catalyst for the Province of British Columbia to embrace the Water Balance Methodology some 15 years ago,” states Richard Boase, Environmental Protection Officer with the District of North Vancouver, and Co-Chair of the Water Balance Model for British Columbia initiative.
“The Water Balance Methodology links actions at the site scale with outcomes at a watershed scale. When the watershed goal is protection of aquatic resources, two decades ago Richard Horner and Chris May proved that it is necessary to first mitigate ‘changes in hydrology’ – that is, changes in how rainwater reaches streams. The Water Balance Methodology addresses flow path differences, and leads to solutions that would maintain watershed health. ”
A Watershed is a Whole System
“So many studies manipulate a single variable out of context with the whole and its many additional variables,” states Dr. Richard Horner, now an adjunct professor at the University of Washington. “We, on the other hand, investigated whole systems in place, tying together measures of the landscape, stream habitat, and aquatic life.” Richard Horner founded the Center for Urban Water Resources Management in 1990.
“The work of Richard Horner and Chris May is standing the test of time,” concludes Richard Boase. “The reason is that they applied systems thinking and looked at watersheds as a whole.”
The Goal: Mimic Natural Water Balance and Protect Water Quality
“When the natural environment is altered by human activities, the slow-release and sponge-like functions of vegetation and soil are lost, such that the balance and flow of water are severely upset,” explains Kim Stephens, Executive Director of the Partnership for Water Sustainability, and principal author of British Columbia’s Stormwater Guidebook.
“Protection of watershed and stream health ultimately involves maintaining the natural proportion of rainwater entering streams via three pathways: surface flow, interflow (shallow sub-surface flow), and groundwater flow.”
“This desired outcome is described as ‘mimicking the natural Water Balance’. Performance targets define how to ‘slow, sink and spread’ rainwater and thereby replicate natural processes.”
More than Surface Runoff
“Defining how much water can be retained, infiltrated, and detained on a lot is a completely different way of looking at the drainage problem and solutions. Surface runoff is a small component of natural watershed function. The key to replicating watershed function and mitigating impacts is understanding ALL flow paths through the landscape. Then, Watershed-based Targets can be distilled into a set of design values that are easily applied at a lot level,” explains Jim Dumont, the Partnership’s Engineering Applications Authority.
“The Water Balance Methodology provides a logical and straightforward way to assess potential impacts resulting from urban development; and analytically demonstrate the effectiveness of the methods proposed for preventing and/or mitigating those impacts.”
To Learn More:
To download a copy, click on Primer on Water Balance Methodology for Protecting Watershed Health. The Primer storyline is structured in five parts:
- Part A: Watershed-Based Approach to Rainwater Management
- Part B: Water Balance Methodology Explained
- Part C: Science Behind the Methodology
- Part D: How to Establish Targets
- Part E: References
For a synopsis of each part, click on the following link to Table 1. Information is presented in a layered fashion to accommodate the interests of a continuum of audiences.