Human and natural pressures on our water quality
The dams we build are impacting ecosystems such as wetlands, lakes, floodplains and coastal marine areas
The dams we build are impacting ecosystems such as wetlands, lakes, floodplains and coastal marine areasBy Victoria Van Cappellen Faculty of Science
Most people know that pollution poses a threat to water quality. But few of us grasp how complex water issues really are. How do human pressures, such as industrial activity, agriculture and climate change, impact the quality of our streams, lakes and groundwater – and ultimately our drinking water?
Philippe Van Cappellen, a professor in the Faculty of Science and the Canada Excellence Research Chair in Ecohydrology, established a multidisciplinary team to tackle such questions when he joined the University of Waterloo in 2011.
What makes this research group unique, though, is the vast range of spatial and temporal scales they bring together in their research. From molecular-level studies of the processes that determine the fate of nutrients and pollutants to global-scale assessments of man-made perturbations of the hydrological cycle.
Take, for example, dams. There are currently in excess of 70,000 large dams worldwide. With the continuing construction of new dams, over 90 per cent of the world’s rivers will be fragmented by at least one dam within the next 15 years.
Van Cappellen and his team are showing how this large-scale damming of rivers is driving major changes in the amounts of carbon and nutrients reaching the world’s oceans. He and his team developed a novel, quantitative modelling approach – the first of its kind – that captures the impacts of more than 70 per cent of the world’s man-made reservoirs by volume.
Their results demonstrate that dams not only impede the transport of nutrients such as phosphorus, nitrogen and silicon along rivers but also retain vast amounts of organic carbon. The resulting changes in nutrient and carbon flows have large, global-scale impacts on the quality of water delivered downstream to ecosystems such as wetlands, lakes, floodplains and coastal marine areas.
“Dams don’t just have local environmental impacts, it’s clear they play a key role in the global carbon cycle and therefore the earth’s climate,” says Van Cappellen.
Van Cappellen is now turning his attention to developing new modeling tools to link land-based human activities to changes in water quality and ecological health in the Great Lakes, the world’s largest freshwater resource.
“The key outcome of this research,” says Van Cappellen, “is a better understanding of how humans impact water quality which, in turn, helps inform more effective management practices that balance the water needs of society with those of natural ecosystems.”