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Setting Performance Targets

RISK-BASED ASSET MANAGEMENT FOR STORMWATER INFRASTRUCTURE: “Communities must determine the desired level of service that they want the drainage system to achieve….and the real cost of providing that level of service,” wrote Hal Clarkson, Certified Asset Management professional


“Our community officials and citizens often do not understand how a drainage system works or the effort required to keep it functioning at an acceptable level of service. As an industry, we have done a very poor job of educating our community on stormwater infrastructure issues, especially on the connection between cost of service and level of service. There is an answer, but it requires a shift in how we as a public works industry do business—and, even more so, it requires a shift in our industry’s mindset,” stated Hal Clarkson.

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BEYOND THE GUIDEBOOK PRIMER SERIES: “Pioneer research in the Englishman River watershed on Vancouver Island led us to look at groundwater differently from a water balance perspective,” stated Craig Wightman, Senior Fisheries Biologist with BC Conservation Foundation, when the Partnership for Water Sustainability released the Primer on Integrated Rainwater and Groundwater Management for Lands on Vancouver Island and Beyond (April 2012)


“The Primer introduces the issue of the ‘unfunded infrastructure liability’. Viewing the watershed through an asset management lens provides local governments with a driver to require that development practices mimic the Water Balance,” states Craig Wightman. “Parksville’s OCP Review provided a great opportunity to formally recognize the value and inter-dependence of the City’s small stream and groundwater resources, and their importance to people and the region’s highly diverse fish and wildlife populations.”

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BEYOND THE GUIDEBOOK PRIMER SERIES: “The Runoff-Based Approach leads to the analysis of runoff and its interaction with the physical aspects considered important to the aquatic environment,” stated Jim Dumont when the Partnership for Water Sustainability released the Primer on Urban Watershed Modelling to Inform Local Government Decision Processes (November 2011)


“It was in addressing the inter-relationship between Runoff Capture and Rate Control that Beyond the Guidebook picked up where the Guidebook left off in 2002. The Guidebook had focused attention upon the site level while assuming there would be benefits to the watershed and streams. By 2007, our knowledge had progressed, and it was clear that the next step was to correlate the rainfall spectrum with all the flows entering tributary streams from the watershed,” stated Jim Dumont.

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WATER BALANCE PERFORMANCE TARGETS: “The flow-duration relationship is the cornerstone of British Columbia’s Water Balance Methodology. As understanding has grown, the methodology has evolved.” – from Water Balance Approach on Vancouver Island (released by the Partnership for Water Sustainability in January 2018)


The Water Balance Methodology has its genesis in the whole-system approach that Dr. Ray Linsley (1917-1990) championed more than 60 years ago. As a professor at Stanford University, he pioneered the development of continuous hydrologic simulation as the foundation for water balance management. “To be useful…the simulation model must be physically based and deterministic, and it must be designed to simulate the entire hydrological cycle…hence it must be a water balance model,” wrote Linsely in 1976.

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FLASHBACK TO 2010 FROM RAIN TO RESOURCE WORKSHOP: “The Water Balance Model allows the user to quickly establish the existing base line that will become the standard used to measure the performance of future development scenarios,” stated Jim Dumont


“The WBM embeds land use zoning from municipal member partners, soil calculator and a new calculation engine QUALHYMO utilizing the Environment Canada climate data that includes rainfall, snow, temperature and evaporation. The easy access and calculation speed combined with the embedded data and information allows the user to easily and effectively plan and design green infrastructure techniques which will achieve the vision and objectives established for the Site, the Development, or Watershed,” stated Jim Dumont.

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Capture Rain Where It Falls: At 2007 Water Balance Model Partners Forum, Ted van der Gulik and Jim Dumont explained development and application of Performance Targets


“We have observed that the power of the Water Balance Model process lies in the conversations that result from users generating a single number – the percentage of rainfall that becomes runoff – that represents the synthesis of any particular scenario. Comparison of scenarios creates understanding, especially when the focus is on the hydrologic implications of the assumptions that underpin those percentages,” stated Ted van der Gulik.

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Capture Rain Where It Falls: At 2007 Water Balance Model Partners Forum, Ministry of Environment's Peter Law provided historical context for Performance Target Methodology


“When we wrote the Guidebook, we recognized there is a material difference in the characterization of surface runoff that originates from an individual development site versus flow that you see at a catchment or watershed scale. What you see in a watercourse is the total flow – that is, water that flows overland plus water that moves through soil until it daylights,” stated Peter Law.

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


“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. This helps planners and designers wrap their minds around how to implement ‘design with nature’ solutions on-the-ground,” explains Ted van der Gulik.

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