Renowned professor Pedro Chaffe, from the Federal University of Santa Catarina (UFSC), made a worrying warning in an article recently published in Science magazine. The article, which was highlighted in the online edition of the magazine, draws attention to the reduction in water availability in the Southern Hemisphere and the worsening of droughts and floods.
The study, carried out in partnership with professor Günter Blöschl from University of Vienna, in Austria, used a new methodology that combines observations of flows from major river basins around the world with terrestrial precipitation data and satellite measurements of evaporation and water storage. The results showed that water availability in the Southern Hemisphere decreased by around 20% between 2001 and 2020.
The researchers highlight that water availability is measured by the difference between precipitation and evaporation, aspects that have been directly impacted by climate change, in addition to being affected by population growth and pollution. However, estimates of these changes are uncertain because precipitation and evaporation measurements tend to be indirect or only locally representative.
The new approach proposed by Chinese scientists has brought more reliability to water availability estimates, which could help improve water management in the long term. The researchers observed that, while in the Northern Hemisphere there was no change in average water availability from 2001 to 2020, in the Southern Hemisphere water availability decreased by 70 mm per year, which corresponds to a reduction of around 20%.
The researchers also attributed these phenomena to conditions such as variation in water temperatures (El Nino and La Nina), which can cause droughts and floods. For example, in 2023, droughts hit the Amazon while, at the same time, southern Brazil suffered floods. These events highlight the importance of effective water management and the need to prepare for climate change.
780 billion dollars in losses
The new discoveries proposed by researchers from China and linked to UFSC studies indicate numerous water management challenges in the Southern Hemisphere. Planning water abstraction for irrigation, industry and residences is one of these challenges. “When water availability in rivers and groundwater falls below water demand, drought conditions are felt by ecosystems and society,” they warn.
The researchers explain that the consequences of the decline in water availability on decadal scales are seen in the decrease in water flow in rivers and groundwater levels across vast stretches of land, which is noted, for example, in much of North America. South.
The study indicates that variations in water availability must be considered on shorter time scales, such as monthly fluctuations. This is because, in regions with seasonal rainfall, evaporation can quickly dry out the soil at the beginning of the dry season, leading to sudden droughts. On the other hand, in a drier climate, rainfall may be more concentrated in rainy seasons, which may lead to flooding rather than groundwater recharge.
“More droughts and floods represent an acceleration of the terrestrial part of the water cycle (a faster storage and movement of water between land, ocean and atmosphere), leading to increased ecosystem degradation through tree mortality and, therefore, greater emissions of carbon dioxide”, they point out in the text.
The article signed by the UFSC professor recalls that this situation has been occurring in the Amazon, further intensifying the effects of climate change, and that the impact of droughts and floods on human beings has been enormous, with more than 3 billion people affected and Damage estimated at more than 780 billion dollars worldwide over the past two decades.
Mitigation and management
Measures to mitigate the effects of reduced water availability generally include investment in infrastructure, such as storage dams and irrigation diversions, as well as solutions based on nature itself and raising awareness of a change in culture. “These solutions could include diversifying water supply and flood protection systems and planning for flexibility in water use to reduce the potential impact of extreme events,” they suggest.
The warning, however, is regarding the human response to water stress, which can have unexpected consequences and which are already noted and recorded by science. “In parts of South America, water use for agriculture has increased and contributed 30% to the increase in dry trends in river flow,” they indicate. In semi-arid regions, this, combined with climate change, could further amplify the crisis.
The researchers state that the challenges in water management caused by the reduction in its availability require a shift from crisis response to long-term proactive management, as advocated in official documents from global entities. “This proactive water management needs to be aligned with global objectives, such as the Sustainable Development Goals, and the experience of local citizens, hydrologists, and water managers.”
| With information from UFSC |
Renowned professor Pedro Chaffe, from the Federal University of Santa Catarina (UFSC), made a worrying warning in an article recently published in Science magazine. The article, which was highlighted in the online edition of the magazine, draws attention to the reduction in water availability in the Southern Hemisphere and the worsening of droughts and floods.
The study, carried out in partnership with professor Günter Blöschl from University of Vienna, in Austria, used a new methodology that combines observations of flows from major river basins around the world with terrestrial precipitation data and satellite measurements of evaporation and water storage. The results showed that water availability in the Southern Hemisphere decreased by around 20% between 2001 and 2020.
The researchers highlight that water availability is measured by the difference between precipitation and evaporation, aspects that have been directly impacted by climate change, in addition to being affected by population growth and pollution. However, estimates of these changes are uncertain because precipitation and evaporation measurements tend to be indirect or only locally representative.
The new approach proposed by Chinese scientists has brought more reliability to water availability estimates, which could help improve water management in the long term. The researchers observed that, while in the Northern Hemisphere there was no change in average water availability from 2001 to 2020, in the Southern Hemisphere water availability decreased by 70 mm per year, which corresponds to a reduction of around 20%.
The researchers also attributed these phenomena to conditions such as variation in water temperatures (El Nino and La Nina), which can cause droughts and floods. For example, in 2023, droughts hit the Amazon while, at the same time, southern Brazil suffered floods. These events highlight the importance of effective water management and the need to prepare for climate change.
780 billion dollars in losses
The new discoveries proposed by researchers from China and linked to UFSC studies indicate numerous water management challenges in the Southern Hemisphere. Planning water abstraction for irrigation, industry and residences is one of these challenges. “When water availability in rivers and groundwater falls below water demand, drought conditions are felt by ecosystems and society,” they warn.
The researchers explain that the consequences of the decline in water availability on decadal scales are seen in the decrease in water flow in rivers and groundwater levels across vast stretches of land, which is noted, for example, in much of North America. South.
The study indicates that variations in water availability must be considered on shorter time scales, such as monthly fluctuations. This is because, in regions with seasonal rainfall, evaporation can quickly dry out the soil at the beginning of the dry season, leading to sudden droughts. On the other hand, in a drier climate, rainfall may be more concentrated in rainy seasons, which may lead to flooding rather than groundwater recharge.
“More droughts and floods represent an acceleration of the terrestrial part of the water cycle (a faster storage and movement of water between land, ocean and atmosphere), leading to increased ecosystem degradation through tree mortality and, therefore, greater emissions of carbon dioxide”, they point out in the text.
The article signed by the UFSC professor recalls that this situation has been occurring in the Amazon, further intensifying the effects of climate change, and that the impact of droughts and floods on human beings has been enormous, with more than 3 billion people affected and Damage estimated at more than 780 billion dollars worldwide over the past two decades.
Mitigation and management
Measures to mitigate the effects of reduced water availability generally include investment in infrastructure, such as storage dams and irrigation diversions, as well as solutions based on nature itself and raising awareness of a change in culture. “These solutions could include diversifying water supply and flood protection systems and planning for flexibility in water use to reduce the potential impact of extreme events,” they suggest.
The warning, however, is regarding the human response to water stress, which can have unexpected consequences and which are already noted and recorded by science. “In parts of South America, water use for agriculture has increased and contributed 30% to the increase in dry trends in river flow,” they indicate. In semi-arid regions, this, combined with climate change, could further amplify the crisis.
The researchers state that the challenges in water management caused by the reduction in its availability require a shift from crisis response to long-term proactive management, as advocated in official documents from global entities. “This proactive water management needs to be aligned with global objectives, such as the Sustainable Development Goals, and the experience of local citizens, hydrologists, and water managers.”
| With information from UFSC |
