The challenge

If global temperatures rise by two degrees, as current estimates suggest, studies show that there will be less snow and more rain, which will have a knock-on effect on the hydrological cycle – the natural flow of water into and out of rivers and streams as affected by precipitation and evaporation.

This will be especially pronounced in areas where snow is the dominant climate condition, where the supply of water is likely to diminish.

What we're doing

Civil engineers from the University of Bristol are examining this connection between climate and river flow, building on an initial study conducted in 420 areas across the United States, covering a broad spectrum of regions where snow is key to socio-economic conditions and to ecology.

This study looked at how rainfall, meltwater, river flow and stream flow was impacted by temperature-induced change, based on data captured between 1948 and 2001. It found that on average, less snowfall did indeed result in reduced streamflow.

“This temperature induced shift from snow towards rain will mean that the average amount of available water could go down, which will have implications for drinking water supplies, crop irrigation and hydropower, as well as river ecosystems. In areas where a significant amount of the hydrological cycle comes from snow, people will find it more difficult to get enough water and so will have to find ways to conserve water, to use it more effectively, or develop alternative water sources,” says Dr Ross Woods.

The team are now working with colleagues elsewhere to further corroborate their findings, and to expand their investigations to other areas where snow is key to the environment including Austria, Switzerland, Sweden, Norway, Finland, Russia, China, Canada, France and Germany.

How it helps

“Our studies remain at the scientific level at the moment so it’s a little too early to talk concretely about the implications,” adds Dr Woods. “But our preliminary findings imply a 10-25% reduction in river flow in snow-dominated areas, which would have very significant implications for water management and for how society might adapt, whether that means alternative irrigation methods, growing different crops or building more water reservoirs to address the water shortages that may arise from temperature-induced changes in the water cycle.”

Investigators

• Dr Wouter Berghujis, Department of Environmental Systems Science, ETH Zurich, Switzerland (formerly Department of Civil Engineering, University of Bristol)
• Dr Ross Woods, Department of Civil Engineering, University of Bristol, Bristol
• Dr Markus Hrachowitz, Department of Water Management,TU Delft, Netherlandsl