State of Global Water Resources 2022
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.
Key findings
- The report provides an independent, global scale quantitative assessment of the status of 2022 w.r.t. hydrological normal (averages) for various variables like river discharge, groundwater, evaporation, soil moisture, inflow to reservoirs etc. with information taken from various sources – In-situ observations, remote sensing, models. The reports is more comprehensive than in the previous year; more hydrological variables organized.
- The report highlights the lack of (timely) availability and sharing of in-situ observations. At the same time shows the potential of innovative solutions for bridging data gaps (modelled and satellite products). However, in 2022, a significantly greater amount of data was available compared to the 2021 report.
- River Discharge & Reservoir Inflow Patterns: Over 50% of global catchment areas and reservoirs displayed deviations from typically normal conditions, of which a majority were drier than usual, aligning closely with 2021 data which also predominantly showed dry to normal conditions. 2022 was a La Nina year, El Nino started in 2023.
- Anomalies in terrestrial water storage, Soil Moisture & Evapotranspiration (ET): The anomalies in Terrestrial Water Storage (TWS) for 2022 and trends since 2002 shows hotspots of decline in (mainly) Ground Water (GW) levels. Throughout 2022, anomalies in soil moisture and evapotranspiration echoed the deviations in river discharge conditions, e.g. Europe experienced increased ET and decreased Soil Moisture during summer, conditioned by a major heat wave and drought.
- Early Warnings For All (EW4All): Measuring and assessing the status of hydrological systems and water resources is a critical prerequisite for the Early Warning System (EWS). Furthermore, reporting key events raises public awareness and provides the basis for EW4All activity.
Highlights
Key Advancements of the 2022 Report
- Inclusion of New Hydrological Cycle Components: The report was extended to include anomalies of groundwater levels, soil moisture, evapotranspiration, snow and ice, and reservoir inflows. Data was obtained from observed data sets, satellite remote sensing, and numerical modelling.
- Expansion of Observational Data: A substantial increase from 38 stations in the previous report to 273 stations in 2022. However, with data from only 14 countries, regions like Africa, Middle East, and Asia remain largely underrepresented. Also more observations on key components of the hydrological cycle are needed for deriving trends and validation of models, e.g. soil moisture, groundwater levels, evapotranspiration.
- Enhanced Spatial Resolution: The analysis now covers more than 1000 river basins globally. Still, some areas, such as the UK, require further refining.
Report Implications and Future Outlook
- The inclusion of new components, based on increased observation data and modeling results, offers a comprehensive view of the status of global water resources. The goal remains to amplify observational data and further the involvement of countries for a better understanding of the water cycle dynamics. Future reports aspire to work with even more in-situ data availability, aided by initiatives like the WMO’s Hydrological Status and Outlook System (HydroSOS).
River Discharge & Reservoirs
River Discharge Status In 2022 (Based on the observed data)
Observed mean river discharge for the year 2022 compared to the period of 1991-2020 (with a minimum of 20 years of data availability, e.g. 2001-2020); the dots are placed at the gauging station location (i.e. gauged basin outlet). The results presented here were derived from the observed river discharge data, which were obtained from NHMS and the GRDC database.
River Discharge Status In 2022 (Based on the model simulations)
Over 50% of global catchment areas and reservoirs displayed deviations from typically normal conditions, of which a majority were drier than usual, aligning closely with 2021 data which also predominantly showed dry to normal conditions. 2022 was a La Nina year, El Nino started in 2023.
The figure shows mean river discharge for the year 2022 compared to the period of 1991-2020 (for basins larger than 10,000 km2). The results presented here were derived from the modelled river discharge data, which was obtained from an ensemble of eight Global Hydrological Model Systems simulations. Inset (bottom left) shows the percentage distribution of the modelled catchment area under the given conditions. Dark gray areas indicate missing river discharge data. The results were validated against hydrological observations wherever available.
Reservoirs Inflow Status in 2022
The figure shows anomalies in the mean annual inflow into selected reservoirs in 2022 as ranked with respect to the historic period of 1991-2020. The results presented here were derived from the modelled reservoir operations data from two GHMs and one hybrid satellite-based and modelling product.
Groundwater Levels
Groundwater Level Rank
The figure shows mean groundwater levels in selected aquifers in 2022 ranked against the historic period of 2013-2022 for selected countries. Reporting units that overlap are symbolized with a stripe pattern, like for instance parts of South Africa shown in the figure.
Source: IGRAC 2023
Groundwater Level Trend
The figure shows groundwater level trends in selected aquifers for the period from 2013 to 2022 for selected countries.
Source IGRAC 2023
Soil Moisture, Evapotranspiration, Terrestrial Water Storage
Throughout 2022, anomalies in soil moisture, total terrestrial water storage and evapotranspiration echoed the deviations in river discharge conditions, e.g. Europe experienced increased ET and decreased Soil Moisture during summer, conditioned by drought.
Monthly Soil Moisture Anomaly in 2022
Monthly anomaly in surface soil moisture in 2022 (Dec 2021-Feb 2022 and Jun - Aug 2022) as ranked with respect to the historical period of 2003-2020. The mask over Greenland from the GLIMS (Global Land Ice Measurements from Space) has been applied.
Source: NASA 2023
Seasonal Evapotranspiration Anomaly in 2022
Seasonal anomaly in evapotranspiration in 2022 as ranked with respect to the historical period of 2003-2020. Note: DFJ 2022 includes Dec 2021.
Source: NASA 2023
Terrestrial Water Storage
TWS = ∑ Groundwater, Soil Moisture, Rivers, Lakes, Reservoirs, Snow & ice storage etc.
Status of Terrestrial water storage in 2022
Terrestrial water storage anomalies in the year 2022 ranked with respect to the historic period (2002-2020), i.e. the same reference period as for the 2021 State of Global Water Resources report.
Note also that Greenland and Antarctica are not included in the maps, as their mass balance trends are large, and therefore overshadow the other continental mass balance trends depicted here.
Trend of Terrestrial water storage between 2002 and 2022
Trends in terrestrial water storage over 2002-2022.
The green hotspots might be due to melting of glaciers and red ones due to over extraction of ground water over the years.
High Impact Hydrologic Events
Selected most notable high impact hydrological events across the globe in 2022 - points indicate flood (blue) and drought (red) events.
Extreme Weather in Asia and Oceania
The Yangtze River Basin in China faced a severe drought, while Pakistan's Indus River Basin witnessed extreme floods. The disaster resulted in at least 1,700 fatalities, with 33 million people affected, and nearly 8 million people displaced. The total damage and economic losses were estimated at US$30 billion. East Australia's Murray-Darling River basin, New Zealand, and Winnipeg basin in Canada experienced several flood events.
Africa's Contrasting Hydrological Situations
While the Greater Horn of Africa dealt with a severe drought affecting 21 million people's food security, areas like the Niger Basin and coastal areas of South Africa saw above-average discharge and major flood events.
Droughts
Severe droughts impacted regions including the USA, Greater Horn of Africa, Europe, Middle East, and La Plata Basin. Europe's drought posed challenges in rivers like the Danube and Rhine and disrupted nuclear electricity production in France due the lack of cooling water.These areas also saw depleted inflows into reservoirs, decreased soil moisture and evapotranspiration levels.
Highlight Stories of 2022
Massive decline in Alps
Numerous European rivers have experienced exacerbating water-related hazards, including floods and droughts. Many of these disasters can be linked to extreme heatwaves causing glacier melt. Droughts in basins such as the Rhine and Danube resulted in water shortages for cooling in power plants, which led to some shutdowns. High evaporation rates have caused a significant drop in lake and river water levels. Glaciers (snow cover area in Apls) have been greatly affected, with examples like Switzerland experiencing a 6.2% reduction in glacial volume over a single summer.
The extent of Alps
Pakistan Floods
Heatwave followed by heavy rainfall and melting of glaciers in Pakistan. Over 33 Million people were affected by flooding in Pakistan, which took place during an exceptionally rainy monsoon period in 2022. July and August 2022 saw almost 200% of normal precipitation. High level of soil moisture can be seen in Pakistan for the months June, July, August (soil moisture image from the report). This excessive rainfall combined with Glacial Lake Outburst led to severe flooding with 1/3rd of the country flooded, and had an economic loss of up to 30 Billion USD and more than 1700 casualties. Due to the flat orography and low drainage capacity, some affected areas remained inundated for several weeks.
Drought in Latin America
The 2022 drought conditions in the La Plata Basin have been the most severe since 1944, impacting agriculture, reducing crop production, and affecting global crop markets. The drought conditions have caused a significant drop in hydropower production in 2022, resulting from low river flows. There were several instances of no water supply in Paraguay during 2022.
State of the Snow Cover and Glaciers
In 2022, the snow cover in the Alps remained significantly below a 30-year climatology, affecting discharge of the major European rivers. The Andes saw declining winter snow, being the lowest in 2021 with some recovery in 2022, impacting water supplies in Chile and Argentina. Observations of Georgia's glaciers, especially the Shkhara, reveal doubling of melting rates over the past years. The Asian Water Tower observed significant glacial melting and changing river run-offs of the Indus, Amu Darya, Yangtze and Yellow River basins, highlighting the deepening influence of climate change on regional water resources.
Subtropical Andes
The winter snow in the subtropical Andes regulates the flows of mountain rivers across central Chile and central-western Argentina and provides the largest volumes of water for recharging the aquifers used on both sides of the Andes, for cities like Santiago (Chile) and Mendoza (Argentina).
Since 2009–2010, the region’s winter snow accumulation has declined substantially, resulting in an extended period of drought locally known as “mega-drought.” Analysis of the snow-covered areas indicates that the winter of 2021 showed the lowest snow accumulation values on record, while during the winter of 2022, the snow amounts reached slightly above-average conditions in some areas with below-average conditions persisting along the central watersheds between ~32° and ~37°S, especially along the eastern side of the Andes (Argentina). As these watersheds contain the most heavily populated urban centres of the region, water shortages have continued, and the local governments have kept water restriction measures in place.
Cryosphere changes and Water Management in Central Asia
Over the last decade, increasing attention has been paid to monitoring of the Central Asian cryosphere due to its critical role in regional water security and vulnerability to global climate change.
Several projects supported by the international community have focused on glacier monitoring, high-altitude hydrometeorological observations, permafrost and seasonal snow cover. It aimed at building and sustaining regional and national capacity, also, enabling long-term understanding of cryospheric changes, monitoring impacts on water resources and other environmental changes.
The Smart & Precise Prognostic Hydrology in Central Asia (SAPPHIRE Central Asia) is an initiative developed to support the Central Asian National Hydrological and Meteorological Services in utilizing data from modern automatic or remote monitoring technologies. It operationalizes the use of cryosphere data by providing a basin-scale snow tracker representing the real-time analysis of snow water equivalent against climatic averages to identify anomalies over the region.
Status of Georgian glaciers
In Georgia, on the ridge of the Greater Caucasus, there are well-developed, high-elevation glaciers (as high as 5 174 m).
Since the 1960s, climate change has led to the disappearance of 29% of Georgia’s glaciers, and the area covered by glaciers has decreased by 30.3%. This has directly affected the water balance, downstream water users, landscape degradation, increased Black Sea levels, and the frequency and intensity of glacial-origin natural disasters, resulting in both material and human losses.
The Shkhara glacier's retreat serves as a compelling example of the accelerated melting of Georgian glaciers in the past half-century. Data from LANDSAT and from field observations by the Department of Hydrometeorology of Georgia show that the speed of retreat of the Shkhara glacier has increased from approximately 6.5 m/year to approximately 14.7 m/year. A similar change was observed for other large glaciers in Georgia.
Asian Water Tower
The Third Pole, encompassing the Tibetan Plateau, the Himalayas, the Karakorum, the Hindu Kush, the Pamirs and the Tien Shan Mountains, is characterized as the Asian Water Tower (AWT), and is the most important and most vulnerable among the water towers of the world. The AWT is the planet’s largest reservoir of ice and snow after the Arctic and Antarctic regions. It provides a reliable water supply to almost 2 billion people.
Glacial melting is accelerating in the region. From 2000 to 2018, total glacier mass in the AWT decreased by approximately 4.3%, in a heterogeneous spatial pattern with the greatest magnitude of melting in the south-eastern Tibetan Plateau and smaller retreat or even gain in mass in the Karakoram, western Kunlun and eastern Pamirs. Permafrost degradation is evident, characterized by thickening of the active layer, rising of ground temperature and shortening of frozen duration of active layer. Snow cover area has significantly decreased, and the snowmelt season has shortened. The number, total area and volume of glacier lakes have increased rapidly as a whole, and the total water mass in lakes has increased by approximately 16% of the total lake volume.
During 1980–2018, annual river run-off across most of the AWT showed a significant increase in rivers such as the upper Indus (+3.9 gigatons (Gt) of river run-off, including glacier melt mass, precipitation and snow melt induced run-off, per decade) but was stable in rivers such as the Yangtze and Salween, while a decline in run-off was observed in the Yellow River (–1.5 Gt river runoff per decade).
Snow water equivalent in Canada
In many parts of Canada, March Snow Water Equivalent (SWE) provides a proxy for seasonally maximum SWE and can be estimated from a combination of assimilated in situ data, satellite passive microwave retrievals and historically forced snow models using the approach reported by Mudryk et al. [i] March 2022 SWE anomalies are presented as percent differences with respect to the 1991–2020 average. Large portions of south-central and south-eastern Canada had above average SWE in March 2022, though there were particular areas of the southern Rocky Mountain and prairie region along the Canada–United States border with well-below-average SWE conditions. Areas of north-central Canada, including parts of the Northwest Territories, had below-average SWE in March 2022, while areas north of the Arctic Circle had SWE varying from slightly below to slightly above the 1991–2020 average.
EW4All (Early Warnings for All)
- None of the EW4All 30 countries had accessible data (Either timely or availability/sharing)
- Most of them were affected by major floods and droughts during 2022 – E.g. In Bangladesh, 7 million people were affected and caused 141 casualties; Sahel floods affecting Niger, Sudan, Chad, as well as the drought in the Horn of Africa affecting Ethiopia, Sudan, South Sudan, Uganda.
- Connection to EW4All The report provides an overview of the status of data availability and encourages data sharing which is crucial for developing meaningful products for the UN Early Warnings for All initiative. The graphical global summaries of various hydrological components help in identifying the hotspots to inform planning, preparedness and management of disasters.
Thanks to partners, WMO Members and experts
