Drier soils and reduced water flow in streams and rivers in rural areas, coupled with more intense rainfall that inundates urban infrastructure, resulting in flooding and storm drain overflows which in turn lead to economic damages are becoming common as the planet warms.
Engineers at the University of New South Wales in Sydney did a comprehensive study of the world’s river systems, based on data collected from more than 43,000 rainfall stations and 5,300 river monitoring sites across 160 countries to find out how rising local temperatures due to climate change might be affecting river flows. Results of the study were published in the online journal Scientific Reports on August 11.
It’s a no-brainer that warmer temperatures lead to more intense storms, that is something that’s been proven – A warmer atmosphere means warmer air and warmer air stores more moisture. Anyone living in the South of the U.S. knows what that feels like, especially on hot and humid days.
And when the rains do come, there is a lot more water coming down and the storms can be intense, sometimes even extreme. But a question has arisen. How come flooding is not increasing at the same rate as the higher amounts of rainfall? The answer turned out to be another equally interesting piece of the water cycle.
Faster evaporation from the moist soils is making them drier, well before any new rainfall occurs. In rural areas, a moist soil is needed to sustain vegetation and livestock. Additionally, in the small rural catchment and urban areas, where expanses of soil are few and far between, the same intense downpours become intense floods, overwhelming storm-water infrastructure and in general, disrupting life.
The emerging reality of the impact of a warming climate
“Once we sorted through the masses of data, this pattern was very clear,” said Ashish Sharma, a professor of hydrology at UNSW’s School of Civil and Environmental Engineering, reports Phys.Org. “The fact that we relied on observed flow and rainfall data from across the world, instead of uncertain model simulations, means we are seeing a real-world effect – one that was not at all apparent before.”
Conrad Wasko, lead author of the paper and postdoctoral fellow at UNSW’s Water Research Centre, says this phenomenon is hitting both rural and urban areas around the world in ways we have not seen before. “People are increasingly migrating to cities, where flooding is getting worse. At the same time, we need adequate flows in rural areas to sustain the agriculture to supply these burgeoning urban populations.”
In 2013, global flood damage costs were over $50 billion. This is expected to double within the next 20 years as extreme storms and rainfall intensify. Added to this statistic will be the increasing numbers of the population moving from rural areas into our growing urban centers. Estimates predict a 23 percent rise in global population growth in the next 20 years, going from today’s 7.3 billion to 9 billion.
Not only will this require the need for added productivity in the agricultural sector, but water security will become a greater challenge everywhere. Sharma points out that e will have to learn to adapt to this reality.
“We may need to do what was done to make previously uninhabitable places livable: engineer catchments to ensure stable and controlled access to water. Places such as California, or much of the Netherlands, thrive due to extensive civil engineering,” he said. “Perhaps a similar effort is needed to deal with the consequences of a changing climate as we enter an era where water availability is not as reliable as before.”
Data analysis for this study was made possible by utilizing rainfall data from the Global Historical Climatology Network, which contains records from over 100,000 weather stations in 180 countries and is managed by NOAA. The Global Runoff Database (GRD) supplied river flow data. The GRD is run by Germany’s Federal Institute of Hydrology and relies on river discharge information collected daily or monthly from more than 9,300 stations in 160 countries, according to Science News Online.
