Global freshwater use
and the water cycle
A planetary boundary not transgressed, but local situations unsustainable
An essential element for all forms of life, water covers 72% of the Earth's surface and represents a volume of around 1.4 billion km3 . Despite its abundance, only 2.8% of this volume is freshwater suitable for human consumption. Most freshwater is found in glaciers, but also in groundwater, rivers and lakes, as well as in the form of water vapour in the air. The proportion of water from atmospheric precipitation that flows in rivers to the sea, or is collected in lakes, aquifers and reservoirs, is a renewable resource. This is known as "blue water", and its global volume is estimated at 37,000 km3 per year ( km3 /year).
Over the course of the twentieth century, freshwater withdrawals for domestic, agricultural and industrial uses increased considerably worldwide, rising from 600 km3 /year at the beginning of the twentieth century to 3,880 km3 /year in 2017. With population growth, they are set to continue rising by 1% a year between now and 2050 (Unesco, 2022).
On a global scale, the rate of freshwater abstraction represents 10.5% of the average annual renewal rate of freshwater resources. It varies greatly from one continent to another, depending on population density and the abundance or otherwise of the resource: Asia (41.3%), North America (8.8%), Africa (6.6%), Europe (4.2%), Australia and Oceania (2.9%), South America (1.7%) - (Unesco, 2022). Around 69% of the water withdrawn is used for agriculture (mainly for irrigation, but also for livestock and aquaculture), 19% for industry (including energy production) and 12% for municipalities (Unesco, 2021).
With climate change, domestic renewable water resources per capita declined by around 20% between 2000 and 2018. This trend is most marked in countries with the lowest per capita resources, such as sub-Saharan Africa (- 41%), Central Asia (- 30%), West Asia (- 29%) and North Africa (- 26%), with risks of water shortages (FAO, 2021).
In view of the stakes involved in water use and the needs of ecosystems, the authors of the planetary boundaries framework have defined thresholds for freshwater use ("blue water") that must not be exceeded at global and local (watershed) levels (Table 6 ).
Table 6: Control variables and planetary boundary for global freshwater use (blue water)
Control variables |
Thresholds and areas of uncertainty |
Global values |
Blue water - Global scale: total volume of freshwater consumed, withdrawn from renewable surface and groundwater resources. |
4,000 km3 of fresh water consumed per year (4,000 - 6,000 km3 per year) |
2,600 km3 of freshwater consumed per year (net withdrawal after discharge) |
Blue water - Local scale: a maximum freshwater abstraction threshold is proposed on a watershed scale and according to the seasonal hydrological regime. |
25% in low-flow months (25- 55%) 40% in the intermediate-flow months (40- 70% ) 55% at high-flow months (55- 85%) |
Source: based on Steffen et al., 2015
Net withdrawal (see glossary) of freshwater on a global scale (2,600 km3 ) remain below the planetary limit (4, 000 km3 ). However, some river basin (see glossary) exceed the limit. It is estimated that 25% of the world's river basins dry up before reaching the oceans, due to the use of freshwater resources in the basins (Molden, 2007).
In 2022, a threshold value for "green water", corresponding to precipitation water absorbed by plants and soils, was added to the "blue water" threshold values (Wang-Erlandsson et al., 2022). Green water plays a major role in the resilience of the biosphere. Soil erosion (reduction in useful reserves) and deforestation are major contributors to the decline in green water. Provisional estimates for green water indicate that the planetary limit has already been crosse (Table7).
Table 7: Control variable and planetary boundary for the water cycle (green water)
Control variable |
Global threshold |
Global value |
Green water: percentage of the earth's ice-free surface in which soil moisture in the root zone deviates from the natural variability observed over thepast 11,000years (much wetter or much drier). |
10% of the planet's soil |
18% of the planet's soils are thought to be in disequilibrium. |
Source: based on Wang-Erlandsson et al., 2022
The disruption of the freshwater cycle on a global scale, combined with the degradation of the resource due to human pressures (abstraction, deforestation, pollution), poses a major threat to food and health security, the ecological functioning of ecosystems (habitat provision, carbon sequestration, soil moisture, etc.) and biodiversity.
France's contribution to overcoming the planetary boundary
Over the 2008-2020 period, total annual withdrawals in mainland France, excluding hydropower and navigation canals, averaged 27.6 km3 /year (Figure 15). Extra withdrawals aiming at ensuring the navigability of canals lead to a total of 32.9 km3 /year on average. A significant downward trend in withdrawals has been observed since the mid-2000s, averaging 1.3% per year since 2008, while the population has been growing. This decrease is essentially attributable to the reduced use of power generation plants, and therefore to the reduction in freshwater withdrawals for cooling purposes. In comparison, global water withdrawals have increased by 1% per year since the 1980s (FAO, 2021).
France's annual net withdrawal of freshwater averages 4.2 km3 over the 2008-2020 period. This net withdrawal accounts for 0.2% of the global net withdrawal estimated at 2,600 km3 . This contribution to the global value appears weaker than France's demographic (0.85%) and economic (2.33%) weight in the world.
Figure 15: Evolution of freshwater abstraction in France from 2008 to 2020, excluding supply to navigation canals and hydroelectricity
Scope: mainland France.
Sources: OFB, BNPE. Processing: SDES, 2023
To identify potential tensions over freshwater exploitation, this global vision has to be completed by considering local limits at watershed scale. They are expressed as a percentage of the natural mean monthly flow and they are based on environmental water flows, i.e. the quantity of water that must be left in the watercourse to ensure the life of aquatic ecosystems. Environmental water flow (EWF) thresholds come from the work of Pastor and al. (2014). The method allocates EWF as a percentage of mean monthly flow, adjusted to the natural variability of river flow during the year. Specifically, it allocates 60% of mean monthly flow as EWF during low-flow seasons, 45% during intermediate-flow seasons and 30% during high-flow seasons. Additionally, an uncertainty range of plus or minus 15% was added to take account of the variability of EWF values obtained by different methods. It was used to infer the uncertainty zone between frontier and limit. For the low-flow period, the uncertainty zone begins when withdrawals exceed 25% of the mean monthly flow, and the limit not to be exceeded is 55%. These thresholds are 40% and 70% for intermediate-flow periods, and 55% to 85% for high-flow periods.
For France, since removals are known by year, the method proposed by Steffen et al. (2015) was adapted. It was applied to the summer season (June to August), on the assumption that withdrawals are highest at this time of year, when irrigation needs are concentrated. At the same time, rivers flows is generally low, representing only 16% of annual runoff volume in mainland France. For the seasonal breakdown of volumes abstracted, it is assumed that all agricultural water use is attributed to the summer period. For other water uses, a quarter of annual withdrawals are allocated to the summer period. To be consistent with the unit of abstraction, flows are expressed in volume, and are naturalized26 by adding net abstraction volumes. The method was applied to the 33 mainland France sub-watersheds of the Water Framework Directive (WFD).
Over the 2008-2018 period, for 15 metropolitan sub-basins, summer abstractions are within the safety zone, with values that remain below 25% of the average summer runof (map3).
26 Flow naturalization involves correcting observed flows for the influence of human use, to obtain an estimate of the natural flow. Here, naturalization involves adding to the observed flow volume the portion of the volume withdrawn that is not returned to the aquatic environment (net withdrawal).
Map 3: Crossing of the local "blue water" boundary in summer, by WFD* sub-watershed, over the 2008-2018 period
*WFD = Water Framework Directive.
Note for the reader: in the Mayenne-Sarthe-Loir sub-basin, more than 75% of years, i.e. more than 8 years out of 11, summer abstractions exceeded 25% of "naturalized" runoff volumes in this zone, and they exceeded 55% of "naturalized" runoff volumes in at least one year out of 11.
Notes: "Occurrence between 25% and 50%" means that 3 to 5 years out of the period, the local boundary in the summer season is exceeded; For the summer season, the local boundary or the local "blue water" limit is crossed when withdrawals represent more than 25% or more than 55% respectively of "naturalized" runoff volumes, i.e. river runoff plus net withdrawal volumes (water volumes "consumed", not returned) for all uses. The summer period covers the months of June to August inclusive. For agricultural use, all withdrawals are attributed to the summer period. For other water uses, summer abstraction is estimated at a quarter of the annual volume.
Sources: Banque Hydro (river flows); Banque nationale des prélèvements quantitatifs en eau (volumes abstracted). Processing: SDES, 2023
Conversely, the local blue water boundary is exceeded at least once in three sub-basins: Mayenne-Sarthe-Loir (once), Moselle (twice) and Côtiers aquitains et charentais (seven times). In the Mayenne-Sarthe-Loir and Côtiers aquitains et charentais sub-basins, abstractions come mainly from groundwater, including deep aquifers, as surface water is less abundant. Consequently, the withdrawal/runoff ratio is high, which explains these results.
For 16 sub-basins, including the 3 whose local blue water boundary is crossed, summer withdrawals fall within the uncertainty zone at least once. The greatest number of exceedances of the 25% threshold are detected years 2011 and 2017. Frequent crossings (at least 3 years out of the 11 observed, i.e. 27%) are explained by various causes: low summer runoff (Charente), which may be associated with predominant irrigation abstraction (Mayenne-Sarthe-Loir, Côtiers aquitains et charentais); high abstraction for drinking water (Seine amont for Paris water supply); high abstraction for cooling power plants (Moselle, Isère, Rhône moyen and Vienne-Creuse).
Although the geographical scale used masks contrasting situations within sub-basins, this initial analysis clearly shows the need to reduce water abstraction, particularly in summer, especially as summer run-off tends to become scarcer with climate change.
Policies and actions to preserve water resources
Water is a common human good, necessary for all forms of life. As a vital resource, water is subject to ancient rules governing its extraction and use, which have evolved over time to limit potential conflicts and preserve the environment.
With the development of hydroelectricity in France, the first "water police" authorization system was introduced in 1898. The Water Act of January 3, 1992 introduced the declaration system and extended the authorization system to a list of installations and structures (nomenclature decree of March 29, 1993, since codified in L214-1 et seq. of the Environment Code). All new or renewed water abstractions with an impact on the environment must be the subject of a file including an incidence study or an impact study. The authorization defines a maximum flow rate and volume.
The 2006 law on water and aquatic environments introduced the notion of instream flow (L214-18 of the Environment Code), which "must not be less than one tenth of the modulus of the watercourse immediately downstream or at the right of the structure, corresponding to the mean interannual flow".
At European level, the first texts focused on water quality. The WFD of October 23, 2000 establishes a more general framework for a comprehensive EU water policy. This directive aims to prevent and reduce water pollution, promote its sustainable use, protect the environment, improve the state of aquatic ecosystems (wetlands) and mitigate the effects of floods and droughts. The aim is to achieve good status for all water bodies. To achieve this, the directive institutes planning at the level of the river basin, i.e. the area into which all runoff water converges. Every six years, a basin inventory is drawn up, identifying water bodies in poor condition27, as well as a program of measures designed to maintain or restore good status. To qualify for "good quantitative status", groundwater withdrawals must not exceed the renewal capacity of the available resource, taking into account the need to supply aquatic ecosystems.
France has 12 river basins, 5 of which are overseas. In each basin, water management is overseen by water agencies in mainland France, and water offices in overseas territories. Together with government departments, the water agencies are responsible for drawing up the Water Development and Management Plan (Sdage), or master plans for water development and management, which plan water management at basin level, and integrate the programs of measures. Each Sdage deals with the management of water abstraction to maintain, or even restore, the good status of rivers and groundwater, and to preserve the ecosystems linked to them: wetlands, transitional and coastal water bodies.
Resource management during low-water periods is based on a set of nodal points and zones, with flow targets for rivers, water level targets for certain coastal marshes and piezometric targets for groundwater. These objectives are set out in the Sdages. At a more local level, water development and management plans (Water Development and Management Plan - Sage) can also adjust these objectives on the basis of a territorial analysis. These values serve as a reference for drought management, as well as for the granting of new or renewed water abstraction authorizations.
27 To be more precise, water bodies "at risk of not meeting the environmental objective (RNAOE)".
When drought occurs, restrictions on water use may be imposed by departmental prefects28. Drought decrees can only be issued for a limited period, for a specific area. They must ensure the exercise of priority uses, in particular health, civil security, drinking water supply and the preservation of aquatic ecosystems, while respecting equality between users in the different departments and the necessary upstream-downstream solidarity of the catchment areas. The aim is to adapt needs as closely as possible to the available resource, by encouraging sober use and seeking solutions adapted to local needs and contexts. The development of water management projects (PTGE) should enable this objective to be achieved, through an approach based on a global and co-constructed approach to water resources over a coherent perimeter from a hydrological or hydrogeological point of view. The PTGE approach is recommended by the French government in all regions where quantitative water management is a real issue, and wherever dialogue between stakeholders is necessary to address this issue of the future.
The action plan for resilient and concerted water management, presented in March 2023, aims to guarantee quality water for all and preserve ecosystems. Its 53 measures are designed to respond to three major challenges: sobriety of use, quality and availability of the resource. The specific challenge of organizing sobriety of use for all stakeholders is reflected in a 10% reduction in abstractions by 2030. In addition, each sector must define and implement water-saving plans.
28 Follow-up on these decrees is available at propluvia.developpement-durable.gouv.fr/propluvia/faces/index.jsp.
Further information
- FAO, 2021. The state of the world's land and water resources for food and agriculture: systems on the brink of breakdown.
- Molden, D. et al., 2007. Trends in water and agricultural development. Pages 57-89 in D. Molden, editor. Water for food, water for life: a comprehensive assessment of water management in agriculture. Earthscan, London, UK and International Water Management Institute, Colombo, Sri Lanka.
- Pastor, A. et al., 2014. Accounting for environmental flow requirements in global water assessments, Hydrol. Earth Syst. Sci. 18, 5041-5059, https://doi.org/10.5194/hess-18-5041-2014.
- Unesco, 2022. United Nations World Water Development Report - Groundwater: making the invisible visible.
- Unesco, 2021. United Nations World Water Development Report - The Value of Water.
- Wang-Erlandsson, L. et al., 2022. A planetary boundary for green water Nat Rev Earth Environ 3, 380-392.
TO ACT
- Eaufrance. Limiting the impact of domestic water use.
- G-Eau. Economic analysis of territory projects for water management (PTGE) with an agricultural component.