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Rebuilt “Water Balance Model” incorporates Climate Change Module (2012)

Note to Reader:

Launched in 2003 by a British Columbia inter-governmental  partnership, the web-based Water Balance Model is a scenario comparison and decision support tool. In 2009, the partnership released a comprehensive document titled Water Balance Model for Canada – The Plan for the Future. This laid out a road map for greatly increasing both the computational capabilities of the tool and its usability in visioning future alternatives for use of water and land.

The federal-provincial Regional Adaptation Collaboratives (RAC) Program then provided core funding over the past 3-year period to implement a substantial portion of The Plan for the Future. The RAC Program has supported coordinated action towards advancing regional climate change adaptation decision-making.

The re-built Water Balance Model now incorporates modules for land use, rainfall capture, climate change, rainwater harvesting, tree canopy interception, stream erosion and drainage infrastructure. This first announcement in a series showcases the Climate Change Module. The article below elaborates on the story behind the module: WHO, WHY, WHAT, HOW, WHERE, WHEN and THE RESULT. To download a PDF version, click on British Columbia Partnership announces that rebuilt “Water Balance Model” now incorporates Climate Change Module 


Mimic the Water Balance

The Water Balance Model (WBM) was developed as an extension of Stormwater Planning: A Guidebook for British Columbia, released in 2002. The purpose of the tool is to help communities establish watershed-specific performance targets, and ‘design with nature’, so that land development mimics the water balance.

The WBM is tailored to multiple levels of users who have a wide range of technical backgrounds, from hydrology experts to planners to stewardship groups. The WBM has launch buttons at three scales; SITE, NEIGHBOURHOOD and WATERSHED.

Adapt and Protect Stream Health

“The Water Balance Methodology holds the key to protecting stream health because it integrates the site with the watershed and stream. It is about finding the right balance between the cumulative volume of rainfall capture on individual sites, and resulting flow rates in streams. Adesired outcome in ‘designing with nature’ is that there will be no net impact on the stream environment,” explained Ted van der Gulik, Chair of the Water Balance Model Partnership, when he announced that the Climate Change Module is now live.

“Looking into the future, local governments need to understand how the rainfall volume and distribution might be impacted over time by a changing climate. Then they will be in an informed position to develop and implement an appropriate adaptation strategy for maintaining a ‘water balance’ that will be effective in mitigating stream erosion and protecting stream health.”

The Team that Developed the Climate Change Module

“The technical team that synthesized our understanding of the science and then developed the Climate Change Module comprised Dr. Charles Rowney, Chris Jensen and Jim Dumont. In addition, Trevor Murdock of the Pacific Climate Impacts Consortium (PCIC) played a key supporting role. This team represents a considerable concentration of brainpower. In particular, we benefitted from the applied research that Chris Jensen has completed in conjunction with his post-graduate studies at the University of Victoria,” emphasized Ted van der Gulik.

Climate Change Module

“The Climate Change Module in the Water Balance Model enables a wide range of stakeholders to make decisions based on a detailed assessment of climate change effects on local drainage, without having to decode the huge body of confusing and contradictory literature. Delivering this capability quickly and easily on the web is a ‘must’ – and this result is a ‘first’,” states Dr. Charles Rowney, Scientific Authority for the Water Balance Model Partnership.

Why the Module Was Developed

“Local Governments are making significant progress in preparing for a changing climate, from vulnerability assessments to comprehensive climate adaptation plans. Throughout these processes, a key challenge has been translating global climate science to local land-use decisions. The new Climate Change Module in the Water Balance Model helps overcome this obstacle,” continues Chris Jensen. He is responsible for advancing climate adaptation in the Ministry of Community, Sport and Cultural Development’s new Integrated Policy Branch.

“Almost all BC local governments have signed the Climate Action Charter. This commits them to greenhouse gas reduction. Also, local government plans and policies typically state that land use and infrastructure planning will consider climate change adaptation. If mitigation is about CARBON, then adaptation is about WATER. Hence, being able to quickly and effectively model how the ‘water balance’ may change over time is a critical input to local government decision processes.”

“We know that hydrologic modelling can be very expensive and time-consuming. We heard from communities that they desired an easy to use tool….one that would help them understand and identify evaluate options for climate adaptation…from site to watershed scale. This need served as a catalyst for development of the Climate Change Module. The RAC Program then funded its development.”

“Now that we have it, the Climate Change Module will support two provincial initiatives: Living Water Smart; and Preparing for Climate Change: British Columbia’s Adaptation Strategy. Adapting to climate change and reducing our impact on the environment is a condition for receiving provincial infrastructure funding. The Climate Change Module will help local governments demonstrate that they can meet this conditional requirement.”

“Decision makers need support when interpreting complex and uncertain climate projections. A core deliverable under the Adaptation Strategy is that the province will develop adaptation planning tools for decision-makers. The Climate Change Module is one such tool,” concludes Chris Jensen.

What the Module Does

“The calculation engine for the WBM enables continuous simulation of the period of record for existing climate stations;  and also those that may be included in future as a result of user requests. This means the Climate Change Module shows the full range of how climate change could be expected to affect watershed hydrology,” states Jim Dumont, Engineering Applications Authority for the Water Balance Model Partnership.

”We’ve always predicted the future, but to date that has very much been a reflection of what fell out of the sky in the past.  Unfortunately, historical rainfall records no longer do the job, since they won’t be typical of the future.  The art form here was to find a way to incorporate meaningful estimates of future precipitation as it will be affected by climate change, and package that in a way that allowed its use in day to day prediction.  Our team has done that,” adds Dr. Charles Rowney.

“The Climate Change Module comprises a single screen in the WBM interface. The user is given a choice of three timeframes consistent with the IPCC’s standard of the 2020s, 2050s and 2080s. The choice may seem simple, but it is deceptive because there is actually a lot going on behind that screen,” concludes Jim Dumont.

“By adopting this approach we are following on, and building upon, the efforts and research provided by leaders in the field of climate change prediction. We are not re-inventing the wheel; rather, we are using the results of scientifically scrutinized research developed by top scientists over the past few decades.”

How the Module Simulates Climate Change

“The module applies data provided by the respected Pacific Climate Impacts Consortium (PCIC) at the University of Victoria. We have taken the complex science of global climate modeling and have incorporated it in a way that we believe makes it easy for engineers, planners and others to understand and apply.  By comparing historic and future rainfall scenarios, communities have a straightforward way to identify potential impacts and assess how green infrastructure can be used to prepare for climate change,” explains Chris Jensen.

“There are many options for a data source. We decided to use PCIC because they are regional experts. The climate change factors have been generated from an ensemble of 15 Global Climate Models (GCMs). This provided an average. Each month in the climate station database has been adjusted based on GCM outputs. This compares with annual or seasonal adjustments that are applied in other tools. The monthly approach is important for the purposes of ensuring an accurate representation.”

“PCIC generated the monthly climate change factors for the three timeframes: 2020s, 2050s and 2080s. Because the WBM is a continuous simulation model, we then had to develop a methodology for translating the monthly factors to 52 time-steps in order to apply a smoothing curve. Otherwise, there would be abrupt steps at each change in month. We now have a set of multiplicative factors for each climate station. This was a significant computational undertaking,” adds Dr. Charles Rowney.

“For each station, we have generated factors for a range of percentiles: 10th, 25th, median, 75th, & 90th. For now, we have limited use to the median. Eventually, we may choose to expose more options as users become more experienced and knowledgeable. In the meantime, they have a starting point for doing basic what-if comparisons.”

Summarises Dr. Charles Rowney, “In practical terms, we have packaged useful estimates of what the future will bring, and made those estimates available to those who want to better understand how their plans will work out in years to come.  This starting point will continue to evolve, but the leap in capability that this represents cannot be understated – we are now specifically planning for not only the changes we can control, like land use and drainage patterns, but the biggest one we can’t, which is the precipitation itself.”

Where Climate Change Can Now Be Simulated

“For the twelve BC and Alberta stations now in the Water Balance Model database, the Climate Change Module generates results for the years 2020, 2050 and 2080. Over time, the Water Balance Model Partnership will be expanding the database to provide more complete geographic coverage,” reports Chris Jensen.

“The ten BC stations are spread over three regions: Victoria and Comox on Vancouver Island; Kamloops and Kelowna in the Thompson-Okanagan; and North Vancouver, Vancouver, Surrey (two), White Rock and Abbotsford. We can potentially add another 22 stations from the Atmospheric Environment Service network. The data analysis is done to develop the climate change factors for each climate station. It is a matter of uploading those stations in response to local government and user needs and expectations. The expanded suite of climate stations will provide the two western provinces with the capability to evaluate the impacts for both existing urban infrastructure and a myriad of alternatives that are possible,” adds Jim Dumont.

The Result

“The Climate Change Module allows communities to easily assess potential impacts and how land use decisions can either reduce or exacerbate impacts,” states Chris Jensen.

“The Climate Change Module is an exciting addition to the family of modules in the WBM.  It builds on the exceptional technical foundation provided by the WBM engine and web technology, and extends it to reflect emerging needs – which is exactly what the latest release of the WBM was designed to do.  We’re making this capability, and others, accessible to people who need them, in ways not previously possible, and I’m looking forward to seeing how this and future developments enabling climate change assessments are applied in practice,” concludes Dr. Charles Rowney.



with federal funding support through Natural Resources Canada’s Regional Adaptation Collaborative Program