Rivers around the world have dried up recently. France’s Loire broke records in mid-August for low water levels, while photos circulating online show the mighty Danube, Rhine, Yangtze and Colorado rivers almost reduced to trickles.
It’s not just the rivers that are running dry, but also the reservoirs they are replenishing, leading to water shortages in many parts of the world, including the UK. Yet floods have wreaked havoc on many of these rivers over the past decade, in some cases just months before the recent drought. So what happens to them?
Climate change takes many forms. The Earth system is interdependent, so when one thing changes, it affects many other things. As atmospheric temperatures rise, weather patterns affect where, when, and how much rain will fall. Consequently, the distribution of water changes from region to region and the rivers adapt accordingly, which affects the amount of fresh water available for consumption.
Fresh water makes up a tiny fraction of all water on the planet, and much of it is locked in ice. While this has been true for as long as humans have existed, climate change is altering where fresh water is found: so that in general, places with plenty get more while places with little get less.
Differences in water distribution are becoming more marked, not only between regions, but also over time. When a river’s behavior becomes more extreme, consistently breaking records for highest and lowest water levels, river scientists say it becomes more “flashy.” Some desert rivers are very flashy and only flow at certain times of the year.
The brightness of a river reflects the amount of water available, which depends on the climate. Although a river may have higher or lower flows for longer periods of time, it can still carry approximately the same volume of water over a year.
Management strategies are usually designed based on how a river has behaved in the past. But we have to consider all the ends of how rivers can flow, because what it seems now is not what it always was, and it is not what it always will be.
Flashy futures?
Rivers are wild streams that have shaped the earth for billions of years, far longer than humans have existed. Rivers naturally change as their environment changes, which includes climate, rainfall, vegetation, sea level, and more. Geologists can read clues to these changes from rocks and landscapes.
We tend to adapt rivers to us more than to them. Engineering measures limit their ability to effect natural changes such as flooding or creating a new course. Urban rivers can be encased in concrete and their flow somewhat straightened, while drains in paved urban landscapes rush water to rivers without the need for it to flow slowly through the ground.
Such man-made changes can make rivers brighter. If there is drought, the water leaves the earth more quickly, while if there is a lot of rain, it accumulates more quickly in one place. As rivers respond to global change, we need to find ways to prioritize their natural coping strategies in how we manage them.
This could involve so-called slow-water strategies such as China’s “sponge cities”: urban areas with abundant trees, ponds and parks to absorb water and mitigate droughts and floods.
There is a lot of work ahead of us to ensure that we cherish and manage a stable and secure supply of water from our increasingly unchecked rivers. Respecting and working with nature can ensure enough clean water – not only for humans, but also for all living creatures and the environment.
