When Conditions Collide

Climate change and land development bind flood and drought to Elbow River basin

By: C. Lacombe

Raise your hand if you wish you had a crystal ball. The brilliant decisions you should make; the prosperous directions you would take and the healthy lifestyle you could adopt all clearly laid out for maximum success.

Sigh… wonderful.

Okay, we don’t have crystal balls and the future will surely throw us curve balls. But, we do have growing aptitude in computer modeling based on existing data and knowledge that are close.

“If the model is built with good data of high quality that truly represents what is happening in the watershed in terms of hydrology, land use and climate change, then we have a tool to run scenarios and see what might happen in the future,” says Dr. Danielle Marceau Schulich Chair in Geospatial Information Systems (GIS) and Environmental Modeling at University of Calgary. Over the past six years, Dr. Marceau led a study of five climate change scenarios in the Elbow River watershed hydrology and a changing land use study. Then, she led a combined study looking at hydrological changes under climate change and land use change to see how these components might affect Elbow River hydrology.

Elbow Falls

“We looked 50 years into the future,” says Dr. Marceau.While she would be the first to caution you that computer modeling is NOT a crystal ball and no one can know the future indisputably, she does stand behind the work.

“A computer model can give us a very good idea of what realistically might happen based on the data we have and scenarios we choose that make sense,” she says. In reality, computer simulated models are the only tool we have to alert us and allow us to adapt.

Dr. Marceau uses them to engage multiple stakeholders who might have different views about land development, climate change and water resource management. She engages people, brings perspectives together and uses the knowledge to build scenarios to investigate. The stakeholders validate the models through feedback to Dr. Marceau’s team during presentations.

Dr. Marceau believes the models can help inform decision makers at various government levels by giving them an opportunity to see how land use decisions might affect local hydrology or vice versa.

“Having an idea of what might happen in the future, might be a very good way for them to make better decisions,” Marceau explains. The future the models show concern her as a scientist and as a citizen of the Elbow River basin.

“Our main results show that between 2040-2060, there is an increase of temperature in every month of the year and an increase of precipitation in winter and early spring,” she says. This creates conditions for higher peak flows in the watershed in spring and a potential shift in peak flows from middle to late spring.

This means more water available in the watershed in April/May and increases the chances of “rain on snow events,” explains Marceau. These create a large amount of water available in the watershed; which is what leads to flood events.

Also, the high flow season will be much shorter in the watershed. She explains that the Elbow River, according to historical data, typically has a flow of about 11 cubic meters per second (cms) for five months of the year – May to September.

“When we run the climate change scenario, we realize that this period would reduce to three months – May to July. This means that in addition to having conditions for flooding in early spring, we won’t have enough water at the end of the summer and beginning of fall,” Marceau explains. This creates conditions where it might be possible to have a flood and a drought in the same year.

The scenario based on business as usual used City of Calgary’s predicted population growth of 26 percent over 10 years. This places pressure to develop land within Elbow River watershed west of the existing built city environment in Rocky View County. This changes large portions of forest and agricultural land into urban development and creates more impervious surfaces; which significantly increases the amount of overland flow and reduces infiltration. She also confirmed that these models predate the announcement of the west Stoney Trail extension.

“Land development might also considerably affect watershed hydrology.” This means that the type and placement of urban development can change Elbow River hydrology. Her team ran a simulation merging two land use change and two climate change scenarios up to 2060. They saw the land use changes and the climate change merge the stream flow impacts and
intensify the early spring flow influences.Elbow

“My view is that, if I was a decision maker, I would very seriously take into consideration the impact of any kind of land development on river hydrology. It’s not just a matter of a developer wanting to develop and people wanting to live there. It’s looking at the whole impact on the hydrology of the watershed and the cumulative effect of land development projects,” she cautions.

“There’s a lot of uncertainty around climate change. We don’t know for sure what will happen, but we have documented facts demonstrating climate change is real and happening faster than we thought 20 years ago.”

Marceau says she believes all levels of government should inform and prepare citizens for coming changes related to climate change. Dr. Marceau lives in Rocky View County west of Calgary and says, “In addition to being a scientist, I’m also a citizen. I see the development going in that direction.” She adds that working on this modeling project created an awareness and concern about what can happen if leaders don’t get serious about considering the hydrological impacts of their decision making.

Visit Dr. Marceau’s Geocomputing Laboratory

Related TED Talk 
Schmidt illustrates the effectiveness of computer modeling
Gavin Schmidt: The emergent patterns of climate change



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