STATE OF GLOBAL WATER RESOURCES 2023

A quantitative assessment of global water resources for the year 2023

September 20, 2024

The hydrological cycle is undergoing significant changes, with increasing global variability.

Mainly due to climate change and human interventions.

There is global variability in the water cycle, and it’s huge and increasing.
To adapt better to the changing hydrological regimes or water environment, we need regular monitoring and assessments of our resources (and our situation).
For better monitoring, we need more investment, i.e. specifically is needed in Africa, Asia, and Latin America.

EW4All – Early Warnings For All

Measuring and assessing the status of hydrological systems and water resources is a critical prerequisite for early warning systems.

This report provides an overview of the status of data availability and encourages data sharing which is crucial for developing meaningful products for the United Nations Early Warnings for All (EW4All) initiative.

The graphical global summaries of various hydrological components help in identifying the hotspots to inform planning, preparedness and management of disasters.

Reporting key events raises public awareness and provides the basis for EW4All activities.

Objective is to establish a globally consistent water information system

United Nations (UN) 2023 Water Conference called for an “Operational Global Water Information System” to support water, climate and land management for socioeconomic resilience, ecological sustainability and social inclusion by 2030.

This report offers a systematic and standardized analysis of the water resources at a global scale, and seeks to create an extensive global dataset of hydrological variables, which includes observed and modelled data from a wide array of sources.

As such, it responds to the UN 2023 Water Conference's call for an "Operational Global Water Information System".

HIGHLIGHTS

Value of this report

Easy to understand global overview and graphical summaries of different hydrological variables at a global scale (standardized, consistent, authoritative).

Help in identification of hotspots at a global scale to inform planning and policy making.

Enable inter-annual comparisons to differentiate short-term effects from long-term trends in the factors driving water distribution patterns.

Inform intergovernmental discussions related to (shared) water resources.

Promote monitoring and data sharing.

Key findings

2023 marked the driest year for global rivers in over three decades, with streamflow levels at their lowest in 33 years, signaling critical changes in water availability. Note that 2023 was also one of the hottest year on records (State of Climate report 2023)

The last five consecutive years have recorded some of the lowest percentages of areas under normal conditions, marking a significant deviation from historical river flow patterns over the past 33 years.

Reservoir inflows have followed a similar pattern like the river flow, reducing the amount of water available for communities and ecosystems, further stressing global water resources.

Widespread dry conditions and elevated temperatures, have contributed to an increase in extreme hydrological events, not only prolonged droughts but significant number of floods around the world.

While the 2023 report benefited from increased data sharing and participation by WMO Members, significant gaps remain in global water monitoring and open data sharing, emphasizing the need for continued progress in these areas, particularly in Africa, South America, and Asia.

Key Advancements of the 2023 Report

The State of the Global Water Resources report is now in its third year and is the most comprehensive to date, with new information on lake and reservoir volumes, soil moisture data, and more details on glaciers and snow water equivalent.

There is increased engagement from WMO Member States in terms of data sharing.

It offers advances in methodology and data sources.

Report Implications and Future Outlook

The report underscores the potential of satellite-based observations and modeling systems to assist countries, especially those with limited monitoring capabilities, and large data gaps, to address these challenges and improve hydrological assessments.

The report seeks to enhance the accessibility and availability of observational data (both through better monitoring and improved data sharing), further integrate relevant variables into the report, and encourage country participation to better understand and report water cycle dynamics.

Future reports are anticipated to include even more observational data, supported by initiatives like the WMO’s Global Hydrological Status and Outlook System (HydroSOS), the WMO Hydrological Observing System (WHOS), and collaboration with global data centers.

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FROM DATA TO THE REPORT

The production of this report involved many stages: technical meeting with global data centres and global hydrological modelling community, data collection, data preparation, data analysis, writing and peer-review.

SCOPE

The number of observed data points received from WMO Members, the Global Runoff Data Centre (GRDC), and other partners for river discharge measurements increased significantly, rising from 273 stations in 14 countries in 2022 to 713 stations in 34 countries in 2023.

Similarly, for groundwater, data for 35,456 wells from 40 countries were collected in 2023, compared to 8,246 wells in 10 countries in 2022.

The Soil Moisture chapter now includes observed data provided by Members of the International Soil Moisture Network (ISMN), which were used to validate modeled results.

PARTNERS – JOINT COLLABORATIVE EFFORT

This report was made possible thanks to various contributions from many and diverse partners.

The 2023 edition includes chapters on River Discharge (Chapter 2), Reservoirs (Chapter 3), Lakes (Chapter 4), Groundwater Levels (Chapter 5), Soil Moisture (Chapter 6), Evapotranspiration (Chapter 7), Terrestrial Water Storage (Chapter 8) and Snow Cover and Glaciers (Chapter 9), each offering global and/or regional insights. Chapter 9 focuses on snow water equivalent and the state of major glaciers worldwide.

The chapter on High Impact Hydrological Events (Chapter 10) provides a global overview of significant hydrological events from 2023, while the final Synthesis chapter (Chapter 11) presents the major findings on the overall state of global water resources for the year 2023.

DATA SOURCES

The report seeks to create an extensive global dataset of hydrological variables, which includes observed and modelled data from a wide array of sources.

OVERVIEW OF DATASETS

For the assessment, the length of the analysis period varied depending on data availability.

WHAT IS "NORMAL"?

For each of the variables presented in the chapters, the anomaly was calculated by comparing the state in the year 2023 to the annual long-term means obtained from the historical period (observed and historical, respectively).

The annual mean of hydrological variables (e.g., river discharge, inflow into reservoirs) for a defined reference period of data were calculated for each year. The ranking of respective variable in 2023 falls under five categories:

“much below normal”
“below normal”
“normal”
“above normal”
“much above normal"

OBSERVATIONAL DATA

Special thanks to all the many partners who shared their in-situ data for the analysis of variables presented within individual chapters.

GLOBAL HYDROLOGICAL MODELLING SYSTEMS – GHMSs

Special thanks to many research institutions who shared the results of their models for the analysis of variables presented within individual chapters.

REMOTE SENSING DATA

Special thanks to institutions who provided remotely sensed data for the analysis of variables presented within individual chapters.

BIG THANKS TO ALL !

Please click each image to fully view and download the infographic.

Note also that other visual materials for social media posts are available for download via Trello: https://trello.com/b/Qn2ELXWo/2023-state-of-global-water-resources-report

River Discharge

2023 DRIEST YEAR FOR GLOBAL RIVERS IN OVER THREE DECADES

The last five consecutive years have recorded some of the lowest percentages of areas under normal conditions, marking a significant deviation from historical river flow patterns over the past 33 years.

2023: HALF OF THE GLOBE HAD DRY RIVER FLOW CONDITIONS

2023 marked the driest year for global rivers in over three decades, with streamflow levels at their lowest in 33 years, signaling critical changes in water availability. Note that 2023 was also one of the hottest year on records (State of Climate report, 2023).

Reservoirs & Lakes

2023: BELOW NORMAL INFLOWS TO RESERVOIRS

Inflow into reservoirs in 2023 generally reflected the overall discharge conditions, with the global balance being mostly below-normal or normal - which means less water available for ecosystems and societies.
Specifically, reservoirs in India, particularly along the west coast, experienced below and much below normal inflows. Similar conditions were observed on the east coast and southern islands of New Zealand. In Australia, the Murray Darling River also recorded below-normal inflows.
In northern and southern America, reduced water availability was evident with lower-than-usual inflows into reservoirs, particularly in the Mackenzie River in Northern America, across the entire territory of Mexico, and in the Paraná River in Southern Brazil and Argentina.
Across the Middle East and Central Asia, inflows into reservoirs remained lower than usual. Contrarily, South African reservoirs saw higher-than-usual inflows following wetter-than-usual discharge conditions.
Northern Europe, particularly Sweden and southern Norway, also experienced increased reservoir inflows. However, in the far north of Norway, inflows were below normal.

LAKES - Anomaly in the volume of 30 largest lakes in 2023

In the Amazon, Lake Coari volume was below normal. Record-breaking heatwaves and reduced water levels caused temperature rise to 34^oC, leading to an algae bloom and causing substantial deaths of pink dolphins.
The volume of Lake Superior, the largest lake in North America, was above normal in 2023, which already manifested in December 2022. Lake Nicaragua, despite the drought event that affected Central America, saw above-normal water volumes in 2023.
In Central Europe: Lake Balaton experienced much above-normal volume levels, as did Lake Peipus in Estonia and Lake Mälaren in Sweden.
In Asia: The Small Aral Sea and Lake Aydar in Kazakhstan and Uzbekistan, as well as Eling Lake, Kaoyu Lake, and Bositeng Lake in China, saw normal volumes in 2023. Hulun Lake and Lake Khanka, shared by China and Russia, also experienced above-normal water volumes. Tonle Sap Lake in Cambodia, located in the Mekong River basin, exhibited above-normal water volumes as well.
Lake Turkana, the largest desert lake shared between Kenya and Ethiopia, had above-normal water volumes, following much above-normal discharge conditions.

Groundwater & Soil Moisture

GROUNDWATER LEVELS in 2023

In South Africa the majority of wells showed above-normal groundwater levels, following above-average precipitation in the recent years, same as for India, Ireland, Australia, and Israel.
Notable depletion in groundwater availability was observed in North America and Europe due to prolonged drought.
Also in Chile and Jordan groundwater levels were below-normal where the long-term declines were due to over-abstraction rather than climatic factors.

SOIL MOISTURE in 2023

Levels of soil moisture were predominantly below- or much below-normal across large territories globally, with North America, South America, North Africa, and the Middle East particularly dry during June-August.
In contrast, certain regions, including Alaska, North East Canada, India, and parts of Russia, experienced much above-normal soil moisture levels.
The northern and south-eastern coasts of Australia, along with New Zealand’s North Island, also had above-normal soil moisture due to wetter conditions and flooding.

Evapotranspiration

EVAPOTRANSPIRATION in 2023

Central and South America, especially Brazil and Argentina, faced much below-normal actual evapotranspiration (AET) in September-October-November, Mexico also experienced below-normal AET and almost throughout the entire 2023 reflecting the severe drought conditions.

Terrestrial Water Storage

TERRESTRIAL WATER STORAGE in 2023

Large parts of the continents experienced below- average terrestrial water storage (TWS) conditions in 2023. Notable exceptions were sub-Saharan Africa, the Tibetan Plateau, and sub-regions of India, Australia and northern South America.

Snow Cover & Glaciers

SNOW COVER

Most catchments (except in Northern USA and far East Russia, Lena catchment) in the Northern Hemisphere had below to much-below normal snow water equivalent (SWE) in March, indicating lower than normal snow availability and below normal spring flood potential.
Seasonal peak snow mass for 2023 was much above normal in the North American continent and much-below normal in Eurasian continent.

RETREATING GLACIERS

In 2023, glaciers lost more than 600 Gigatonnes of water, the largest mass loss ever registered in the last five decades.
Following 2022, 2023 is the second consecutive year in which all glaciated regions in the world reported ice loss.
Observed summer mass loss over the past years indicated that glaciers in Europe, Scandinavia, Caucasus, Western Canada North, South Asia West, and New Zealand have passed peak water, while Southern Andes (dominated by the Patagonian region), Russian Arctic, and Svalbard seem to still present increasing melt rates.

GLACIER PEAK WATER

As glaciers respond to warming, their runoff initially increases, reaching a 'peak water' point, after which it declines as glacier volumes shrink (Huss and Hock, 2018). If temperatures continue to increase, the glacier will disappear, and with it, its hydrological contribution.
This trend is expected globally, with significant reductions in glacier runoff by the century's end, particularly in Central Asia and the Andes, where glaciers provide over 50% of basin runoff. Many regions with smaller glaciers have likely already passed peak water (Huss and Hock, 2018).

High Impact Events

HIGH IMPACT HYDROLOGICAL EVENTS IN 2023

Widespread dry conditions and elevated temperatures, have contributed to an increase in extreme hydrological events, not only prolonged droughts but significant number of floods around the world.
Africa was the most impacted by extreme hydrological events in terms of human lives lost: In Libya where two dams collapsed due to flood, over 11,000 lives were lost and the event affected 22% of the population.
The floods also affected the Horn of Africa, Democratic Republic of Congo and Rwanda, Mozambique and Malawi, leading to additional > 1600 deaths.
Southern USA, Central America, Argentina, Uruguay, Peru and Brazil were affected by widespread drought conditions, which led to 3% gross domestic product (GDP) loss in Argentina and lowest levels observed in Amazon and in Lake Titicaca.