The impact of climate change on rivers and lakes

Climate change and human interference are altering our water systems on land. Lakes and rivers are undergoing dramatic transformations which impact nature, ecosystems and ultimately us. Rivers, streams and lakes give us water and food, rich biodiversity and sustain industries, so when they change, you can expect disruption. Can scientists help work out solutions before our waterways are dangerously dried up and degraded?

By Richard Forsyth

Whilst we often think of climate change in terms of rising sea levels and coastlines under threat, climate change is also fundamentally changing the planet’s precious lakes and river systems.

Consider that 97 percent of the water on Earth is saltwater, leaving only three percent as fresh water. Around two thirds of that fresh water is frozen in glaciers and ice and most of the remaining is subsurface groundwater. That leaves a tiny fraction as water above the ground or in the air.

The warming effect of climate change is transforming the water cycle and when, where and how much precipitation occurs. It triggers severe weather events as more water evaporates, so with the higher levels of water vapour there is more frequent and heavy rainfall, which in turn can lead to flooding. The drier land with less vegetation means the soil does not so easily absorb the downfalls. Add farming fertilisers to the runoff from fields into waterways and it can lead to algae blooms which can be detrimental to the natural wildlife in the rivers and lakes. Rivers and lakes affected by climate, can change the weather and affect environment in and around the water.

In more than one way, today, our natural water sources are altering in nature, and faster than we could have predicted. Combine this with our interference with nature’s water systems, building dams and excessively using fresh water and you have the makings of a potential crisis.

No snow, no meltwater

High-up glacial meltwater is often the source for rivers but with less precipitation and warmer climates, the ice and snow vanishes. This leads to some rivers and lakes drying up and even disappearing, as with Lake Poopó, which was Bolivia’s second biggest lake prior to 2015. This was largely due to the loss of the Andes glaciers, which provided the meltwater. The huge lake was reduced to marshland after December 2015 and is unlikely to recover. The lost Bolivian lake provides a glimpse at a scenario that is likely to be repeated across the world.

Rivers are facing the same challenges as lakes. Pakistan held an urgent online meeting, organised by Global Water Operators Alliance in June, precisely to acknowledge that water from melting glaciers has been affected by climate change and the country’s river water was running dry. Ironically, in conjunction there have been unpredictable torrential rains which led to flooding in urban areas and to the destruction of crops.

About half the world’s river networks are running dry. To highlight this closer to home in Europe, impacts of this nature have already begun. The Rhine and the Danube for example, have headwaters that originate in the Alps. The Alpine glaciers of Europe are melting faster than the snow can top them up, due to the warmer temperatures. In recent years there have been unprecedented low water levels in these rivers. In 2018, Germany’s Rhine levels were so low that shipping was impossible, which had a knock-on impact for industry, cutting off factories from supply ships. In 2020, at one key point in the river at Kaub, it dropped to about 1 metre on 3 June, the lowest in two decades. Researchers at the University in Canada found that over half of the Earth’s rivers stop flowing for at least one day a year and more are expected to run dry. In this study, the reasons for halted flow vary, from freezing up, such as in the Himalayan streams, drying out as in the Sahara or when there is too much water extraction for irrigation of crops. This is a situation expected to get worse with escalating climate change. The World Health Organisation estimates that half of the world population will be living in areas that are water stressed by 2025.

Washed away

As previously mentioned, on the other side of the challenge of drying up rivers and lakes, climate change can increase rainfall. This can cause some rivers to burst their banks and flood, at times which are not in line with established ecosystem processes. Researchers from University of Glasgow and Umeå University in Sweden found that the thermal growing season for plants (where temperature rises consistently above 5°C) was starting earlier in the year, closer to the time when the highest river floods occurred. This means that seeds and vegetation get washed away, which in turn denies a food source for animals, with implications for farming too.

The changing influences of water

Rivers and lakes are changing all around the world, that is clear now. A recent study published in the journal Science, by an international team led by ETH Zurich, analysed 7,250 measuring stations around the world and combined with computer modelling, the study proved river flow changed systematically between 1971 and 2010. Some rivers were drying out and some were increasing volume. The common factor was that significant changes were occurring. Patterns emerged from the study revealing the nature of the changes. Regions like the Mediterranean and north eastern Brazil had become drier and in other places like Scandanavia the volume of water had increased. Studies like this can also provide data for projecting ahead, and that can be crucial for management of land, resources and to see how migration patterns of animals and people could occur.

The simple truth is the world’s demand for water will overtake supply by 40 percent in 2030.

One solution, one that is almost an inevitable outcome, is that we will need to address how we use water and essentially ration and recycle it, to be smarter with it.

Solutions to adapt

Other projects are also accumulating data on river changes. For instance, the EU project, DRYvER, started in 2020 and set to finish in 2024, has an aim to develop strategies to mitigate climate change effects on drying rivers, with guidelines and tools.

The big problem is not just about the volume of water or more often than not, the lack of it, it is that the health of rivers and lakes is in decline. Preventing and reversing the destruction of natural habitats through both climate impacts and manmade projects has become an urgent motivation for taking actions, for the EU. Many aquatic species are under threat of extinction. The World Wide Fund for Nature (WWF) stated that 60 percent of EU rivers, lakes and wetlands are not healthy and Europe in particular, has the most fragmented river landscape on the planet. This has led to devastation of biodiversity. Freshwater species populations have shrunk by 83 percent since the 1970s.

Countering this problem has long been a mission for The EU Water Framework Directive (WFD). From the year 2,000 it has and still is, striving to bring most of the EU rivers, lakes, wetlands, groundwater and coastal waters back to good health by 2027. Part of its strategy is minimising changes to natural water systems and preventing, where possible, hydropower projects that are destructive to natural water habitats. It will also try to exert influence to minimise overuse of freshwater resources for agriculture and industries with heavy water usage

Removing dams

To intensify the challenge of drying rivers, dams can cause more damage to river environments, destroying natural habitats and interfering with natural flow. Whilst damaging to natural environments, the hydropower sector is thriving, as a way to increase energy supplies to locations and attract industry. There are 21,387 hydropower plants in Europe with 8,785 plants planned and being built.

Blockages and dams are prolific in Europe, and there is estimated almost one kind of barrier for every kilometre of river. These barriers are often not necessary, and yet their effects include blocking fish migration, interfering with sediment and nutrient flow and generally degrading natural rivers.

Taking away blockages like dams, or at very least not increasing barriers, is a solution to stem the serious decline in nature. With this as a driver, European Rewilding Network (ERN) is looking at ways of restoring rivers to their natural, free flowing state, with a focus on removing nonessential dams. It has been estimated that in Spain, France the UK and Poland, there are around 30,000 dams that are obsolete.

Organisation’s such as WWF are pressuring to stop the development of new hydropower projects, and instead, to focus on refurbishment of existing plants and changing to low impact alternatives like solar and wind power. The WWF is also advocating to stop subsidies and state financing for new hydropower in Europe, to take away the lure of attractive incentives.

A change of attitude

One solution, one that is almost an inevitable outcome, is that we will need to address how we use water and essentially ration and recycle it, to be smarter with it. Household water usage will need to become a focus for water conservation. Devices like dishwashers and washing machines can use excessive amounts of water. Industry and agriculture also require huge amounts of water. Farming makes up for 70 percent of water consumed and a lot of that is wasteful and unnecessary. Every industry requires water and the sectors that consume the most water can be surprising. Consider the fashion industry uses around 79 billion cubic metres of water per year (2 percent of all the freshwater extraction around the world) and this could be doubled by 2030. Focusing on conservation and recycling of water for home and business use is a key part to ensuring water security around the world, including Europe. Smart designs that facilitate recycling water, such as rain collection systems on roof tops, will also be a key to future considerations when fresh water becomes scarcer. Looking at options such as groundwater extraction, where water is stored beneath the earth’s surface, needs serious consideration for dry sites that will spread throughout the world, from California to the Nile Delta.

On a global scale, less than half of all waste water is collected and less than 20 percent of that is treated before being released back into the cycle. Untreated water can do further damage to water systems and nature. The simple truth is the world’s demand for water will overtake supply by 40 percent in 2030.

Of course, we do have the technology for desalination, which removes salt from saltwater but the technology uses a lot of energy and is prohibitively expensive. Currently, desalination does play a part in water supply strategy in places where freshwater is in very short supply, like The Middle East and North Africa.

For a growing global population, water shortage will be an ever more urgent issue to address, not least for its relevance to food security. The lakes and rivers of the planet are in a state of transformation, the meltwater is drying up, and now is the time to innovate, conserve and plan for a world that is going to see a great deal of change in natural water sources, and many more drier regions with fewer rivers and lakes.