WATER SUPPLY IN BRITISH COLUMBIA’S CHANGING CLIMATE: “Since 2000, summer precipitation has dropped about 20 per cent. This step change is unusual,” stated Hans Schreier, a professor emeritus of land and water systems at the University of British Columbia (July 2021)

Note to Reader:

After a period of relative hydro-climatic stability, changes in the composition of the Earth’s atmosphere have resulted in the acceleration of the global hydrologic cycle with huge implications for every region of the world and every sector of the global economy. We can expect deeper, more persistent drought punctuated by flooding. In 2015, the drought that extended over most of the year from winter through spring and summer, and geographically from Vancouver Island to Manitoba and from Mexico to the Yukon suggested we had crossed an invisible threshold into a different hydro-meteorological regime in Western North America. Every year since, with the exception of 2020, has confirmed British Columbia’s new reality: longer, drier summers and warmer, wetter winters.

Mother Nature is ticked off. Can you blame her?

“Fires. Floods. Mudslides. Rivers and reservoirs drying up. Record heat. Rising shorelines. Glacial melting. The Earth is in peril, and many are finally realizing they can no longer think of Earth as the open armed goddess dispensing blessings and bounty to us — especially if we take no steps to curb the activities and habits that have sent carbon dioxide emissions soaring,” wrote Michele Norris in her column published by the Washington Post on July 30, 2021.

“The defining struggle of our time, and our future, will be the tension between Mother Nature and human nature. So, more of us need to think differently about who and what we are dealing with here. That seems to have finally begun.”

The New Climate Reality in British Columbia

“Michele’s second quotable quotable, about the need to think directly, provides relevant context for what we can and must do to adjust to longer and drier summers in British Columbia,” stated Kim Stephens, Executive Director, Partnership for Water Sustainability in British Columbia. “Conceptually, it sounds straightforward  to state that we must get our seasonal water use in balance with a changing water cycle. However, pulling this off will require doing many little things over time. Cumulative benefits do add up.

“To provide us with an attention-grabber, Hans Schreier, professor emeritus of land and water systems at the University of British Columbia, has done some invaluable number crunching. In easy to understand terms, Hans has quantified what our new climate reality means from a water supply perspective. He has examined historical precipitation data for multiple stations. He has developed a comparison of long-term averages for two periods: before the year 2000 and since 2000. This comparison provides us with an order-of-magnitude.”

Unusual Changes in Summer Precipitation in the Lower Fraser Region of British Columbia

“Most long-term climate stations within the Lower Mainland region of British Columbia have a 50 to 75-year record. Over this time period, there had been an increasing trend in summer precipitation (May-Aug) until around 2000. Since that time (2000-2020), however, there has been a step change to a lower rate of precipitation of around 20 percent,” explained Hans Schreier.

“This trend is consistent for all of the 8 stations that I examined, namely: Vancouver Airport, Vancouver Harbour, West Vancouver, Gibsons, Squamish, Pemberton, Abbotsford, and Agassiz.”

“This step change is unusual and one of the possible explanations could be that in 1998-99 we had a major El Nino event, which could possible have influenced the ocean current and jet stream to change the phase of the summer precipitation.”

“This step change is not visible for the winter precipitation, which shows no real changing trend.  This explanation is of course speculative and much more research is needed to provide a more concise explanation.”

“What is also of importance is that there has been a consistent increasing temperature trends over the entire 50 to 70-year record and this should be of concern for agricultural and municipal water use.”

In media interviews, Hans Schreier commented on recent list of climate disasters, including fires in western North America, and floods in China and Europe. “The drought this year (2021) is just one of many unusual weather patterns around the world being driven by climate change.”

He said it’s becoming increasingly difficult to predict weather because old, reliable patterns are breaking down. “That’s going to be the norm, and it’s going to be continuous variability — and it’s those extremes which are really worrying.”

Soil is a Primary Water Management Tool

Hans Schreier is an advocate for restoring the soil sponge in urban areas.

“Soil can hold more water than all the rivers in the world. If you build a new house, what is the first thing you do? You remove the topsoil. Then you bring in the bulldozers and compact everything. And then, you put in the lawn, which is about 30 millimetres of soil.

“Why not have a bylaw that for every new house, before they put in the lawn, they have to have 300 millimetres of topsoil. That would save you massive amounts of irrigation water.” These measures would all reduce pressure on Metro Vancouver’s three reservoirs during the summer, Schreier said.

“We have options, and most of the options are not expensive. But it means public education and the willingness politically to bite the bullet and do this properly.”

A Shrinking Safety Factor

“Climate change has aggravated an existing vulnerability related to seasonal supply of water in BC. Over time, the safety factor has been shrinking. While it rains a lot in BC, we do not have an abundance of supply when demand is greatest. In addition, the mountainous nature of BC’s geography means that BC communities are typically storage-constrained, and what storage they do have is measured in weeks to months,” added Kim Stephens.

“As of 2015, we clearly crossed an invisible threshold into a different hydrometeorological regime in Western North America. Winters are warmer and wetter. Summers are longer and drier. This new reality has huge consequences for water security, sustainability, and resiliency.”

“A generation ago, water supply managers could reasonably anticipate that three months of water storage would be sufficient to maintain supply during a dry summer. Today, however, a 6-month drought is a very real likelihood, and on a repeating basis. In the meantime, populations have also grown in the major centres.”

Where to Focus Resiliency Efforts

“Because many factors are in play, an over-arching goal for sustainable water supply management would be to build in resiliency that addresses risk,” continued Robert Hicks, City of Vancouver. “If communities are vulnerable on the supply side, then it would make sense to build in resiliency on the use side. There is no silver bullet. Communities need to do many little things. Over time the cumulative benefits of doing many things do add up.”

“One of the little things that would yield cumulative benefits is requiring a foot of soil for all development sites so that there is a sponge that reduces water need and prevents water runoff.”


The Summer 2021 issue of the Asset Management BC Newsletter includes an article co-written by Kim Stephens and Robert Hicks to open minds about foundational concepts upon which to build climate adaptation strategies that result in whole-system water management outcomes.

To read the complete article, download a copy of Restore the Balance in Water Balance – Climate Change is Another Variable When Planning for Sustainable Service Delivery, Dealing With Uncertainty, and Managing Risk

In addition, download a copy of Living Water Smart in British Columbia: Dealing with Uncertainty and Managing Risk.