This chapter presents the main results of the evaluation of the risks as well as the policies implemented in the Paris metropolitan area to address drought-induced water scarcity risks in the context of climate change. The assessment carried out by the OECD identifies 22 recommendations to help the area strengthen its resilience to future droughts.
Adapting the Paris Metropolitan Area to a Water‑Scarce Future
Abstract
1.1.1. Drought risk has increased in the Paris metropolitan area
Droughts are a known phenomenon in the Paris metropolitan area. Droughts have occurred and were documented as early as the 16th century. One of the most severe droughts occurred in 1921, when the region’s major river, the Seine (Box 1.1), experienced a 50% reduction in water flow during the summer, and the region endured 12 months of dry soil. Were such a drought to occur today, it is estimated that water use restrictions would have to be imposed on irrigation, navigation, and industrial water use for over 150 days to maintain water supply for critical uses such as potable water (EPTB Seine Grands Lacs, 2021[1]). Since then, significant droughts occurred in 1959, 1976, 1991 and 2003, where nearly 40% of the region’s territory was affected by prolonged soil dryness on that latter year (Météo France, 2022[2]). More recently, in 2019, a major summer heatwave coupled with a spring with below average rainfall led to restrictions on water abstraction for agricultural use in almost half the region. In 2022, after a particularly dry winter, recording rainfall deficits of up to 41% compared with the 1981-2010 average, a prolonged and severe drought occurred, lasting for one year and causing 23% of the rivers in the region to be under the crisis thresholds due to their low flow rates, and 10% of rivers outside Paris with no visible flow (DRIEAT, 2023[3]).
Annual mean precipitations in the Paris metropolitan area over the period 1901-2021
Source: Authors based on World Bank data.
In the past, the region has felt drought impacts mostly through crop losses and structural damages to buildings. The historical agricultural drought of 1976 and 2003 reduced field crop yields by around a third and 60% respectively (Kapsambelis, 2018[4]). The cumulative cost of clay shrinkage and swelling phenomena responsible to structural damages on buildings, especially individual houses, reached almost EUR 2 billion for the period 1995-2019 (DRIEAT, 2023[5]), and represented an average annual cost 1.5 times higher than that of floods for the same period (Caisse Centrale de Réassurance, 2020[6]). In 2022, the region also experienced short-time navigation disruption on canals via the grouping of boats, and restrictions on the use of water for watering gardens, sports facilities, vegetable gardens, car washing, or even irrigation. These restrictions may extend to fluvial goods and tourism transportation, as well as industrial, agricultural, energy and drinking water production related water withdrawal in the event of a more severe drought.
Regional economic expansion has increased demand for water. The Paris metropolitan area produces a third of France's GDP. Half of its surface area is dedicated to agricultural production, increasingly relying on irrigation (Box 1.1). Water withdrawal for agriculture has more than doubled over the period 2012-2019 (Ministère de la Transition Ecologique et de la Cohésion des Territoires, 2020[7]). The regional manufacturing industry, which accounts for 6% of the regional GDP, is heavily dependent on water as a production factor and for cooling (Institut Paris Région; INSEE; CCI, 2021[8]). The Seine River is a particularly important water resource for the region's economy, as it transports more than 8 million tourists in the region every year (Haropa Port, 2023[9]). A growing volume of goods, accounting for 40% of France’s river freight transport in 2022, is transported on the Seine River (Voies Navigables de France, 2022[10]). Lastly, water from the Seine River is also used for energy production by certain heating and air-conditioning systems which are essential for vulnerable populations and health services. Drinking water constitutes 62% of all water uses in the region, while economic activities (including manufacturing) and energy account for 28%. Irrigation constitutes a minor share of water withdrawals (Figure 1.2).
Average annual water withdrawals 2018-2022
Note: All water withdrawals have been considered except those for the dams which would otherwise constitute 95% of all uses but are almost neutral in terms of consumption.
Source: Authors based on data of the national database of water withdrawals.
Demographic changes and subsequent urbanisation have contributed to reduced groundwater levels. The region is the most densely populated and urbanised region in France. It accommodates nearly 19% of its population and has a population density that is 10 times higher than the French national average (INSEE, 2022[11]). The regional population growth was characterised by significant urban sprawl outside of the city core (Institut Paris Région, 2021[12]), which contributed to increasing soil sealing, reducing soil permeability and disrupting the recharge of aquifers as well as the natural flow of rainwater towards watercourses. 21% of the region’s territory consists of built-up areas, mounting to 84% for the city of Paris. This compares to a 9% average in France (Agreste, 2021[13]) (Figure 1.3). Therefore, only 30% of rainfall infiltrate the soils, which is lower than the levels experienced in other French river basins (Agence de l'Eau Seine Normandie, 2022[14]).
Water resources in the Paris metropolitan area come from the Seine-Normandy River basin. The basin covers 18% of France’s surface and consists of the Seine River, its tributaries (the Yonne, Marne, and Oise), as well as smaller rivers and streams. The source of the Seine is located at an altitude of 446 meters, around 300km from Paris. It flows for 776 km in a northwest direction and empties into the English Channel. The Seine has played a crucial role in land development, trade, and industrial and agricultural activities with processing industries (e.g., petrochemicals) and manufacturing industries (e.g. automotive, aerospace) that have developed along the river. The Paris metropolitan area accounts for 65% of the river basin’s population. In particular, wetlands make up 2.8% of the region's area and play a crucial role in water purification and regulation.
Source: Authors based on the national database of water withdrawals and CORINE Land Cover 2018.
The pressure on the Seine Normandy basin’s water bodies is significant. The average surface resource per capita generally lower in the Seine-Normandy River basin than in other French river basins. Hence, while the per capita water abstraction in the Seine-Normandy River basin is below the levels observed in other French basins (Table 1.1), the anthropic pressure on water resources is relatively higher in the Seine-Normandy River basin than in other parts of France.
The basin areas of the Seine, Adour, Rhone and Loire (2020)
Note: The average surface resource per capita is more than four times lower in the Seine-Normandy River basin than in the Adour-Garonne or Rhone-Mediterranean ones. Hence, while the volume abstracted per capita is two times lower in the Seine-Normandy River basin compared to the two latter ones, the anthropic pressure on water resources is higher in the Seine-Normandy river basin.
Source: Authors based on data from the national database of water abstractions (BNPE) and river basins official documents.
1.1.2. Climate change will increase the risk of droughts in the future
Climate change has contributed to heightened drought risk in the region. While average yearly rainfall has slightly increased, rainfall patterns are characterised by significant variability from year to year. In addition, the annual average temperature has risen by more than 2°C since 1990. This has contributed to higher evapotranspiration and an average soil moisture decrease of 5% since 1990. Similarly, dry soils were observed 110 days on average in the region over the period 1991-2020, an increase of more than 20% compared with the previous 30 years (Météo France, 2022[2]).
While a severe drought such as the 1921 episode did not occur again, climate change will make it a likely event to occur by 2050. Climate change projections for the Paris metropolitan area anticipate decreased summer precipitation and increased evapotranspiration due to rising temperatures (Figure 1.4). Expected greater climatic variability may lead to more intense but shorter rainfall events throughout the year, which is less effective for groundwater recharge (Boé et al., 2018[15]). Evapotranspiration, resulting in drier soils, is expected to increase by 16% in 2050 and 23% in 2100 compared to annual daily averages from 1970-2000 (Agence de l'Eau Seine Normandie, 2023[16]). The combined effects of climate change will lead to lower regional river flow rates as well as a decrease in soil moisture and groundwater levels.
Average annual temperature deviation compared to the period 1970-2010
Source: Authors based data from the web platform DRIAS, “the futures of climate” which is the French public database provided by the national meteorology agency Météo France. The data used in this figure reflect the climate scenarios RCP1 4.5 and 8.5.
1.1.3. Projected drought levels and water needs are threatening regional resilience to water scarcity
To date, the Paris metropolitan area has benefitted from a remarkably resilient water supply system. Multiple water supply infrastructures have prevented the Paris metropolitan area to be negatively impacted by droughts in the past. The region benefits from four major reservoir lakes that maintain river flows when precipitation levels are low. They have secured up to 50% of the water levels of the Seine River during the 2022 drought. While fluvial transport on other major European rivers, such as the Rhine, was halted, navigation on the Seine continued. Additionally, part of the region is covered by an interconnected underground water supply network, which draws on a variety of ground and surface water sources and ensures a continuous supply of drinking water in the event of a production interruption induced by natural or human hazards, at one or more of the network's potable water production plants.
However, socio-economic development is expected to increase water demand in the future. The population of the Paris metropolitan area is expected to grow by 5% by 2050 compared to 2020 (INSEE, 2022[17]), which in turn is expected to increase potable water demand. Agricultural irrigation needs are expected to increase by 45% by 2050 to cope with hotter and drier summers and to ensure a stable production of vegetables and fruits for local consumption. Growing cooling production dependent on Seine water for air conditioning may also strain water resources. Similarly, the region expects river transport to double or triple by 2050, which could make the maintenance of necessary water flow and levels more important.
Faced with more severe drought risks, there are growing concerns that current drought resilience levels cannot be maintained in the future. It is estimated that the lakes would be recharged to only 28% of their capacity in the event of a drought equivalent to the 1921 drought (EPTB Seine Grands Lacs, 2021[1]). In addition, critical levels of soil moisture would require increased irrigation for crop production, at a time where irrigation would be restricted. Most activities depending on the rivers would be affected with up to 60 days of restrictions. Similarly, assuming the continuity of current trends in groundwater level depletion by 2050 and 2100, severe water restriction on activities depending on these resources could be experienced up to a whole year. Hence, faced with severe droughts and increased water needs, the region may lack access to sufficient water resources and in turn experience water scarcity.
1.1.4. Future drought episodes may generate important economic losses
A drought like the one in 1921 would cause major water shortages. Building on the 1921 drought episode, this report developed three climate change drought scenarios to estimate their potential impacts on river flows, soil moisture, surface water temperature and underground water levels induced by projected regional climate change (Table 1.2). The baseline scenario mimics the 1921 drought river flow rates. The median scenario reflects the simultaneous occurrence of a drought and a heatwave by introducing an elevated water temperature factor. Lastly, anticipating a worsening drought and heatwave risk by 2100, the adverse scenario reduces the 1921 river flow levels by 20% and increases water temperature by 2°C. For soil moisture, in the absence of data for the 1921 drought, the 1976 agricultural drought has been used as a reference. Underground water levels have been projected for 2050 for the baseline and median scenarios and 2100 for the adverse scenario. Direct economic impacts of these three water scarcity scenarios have been computed for each of the following sectors: energy production, fluvial transportation, water production and treatment, agriculture, industry and buildings. These direct impacts are then used as inputs to a macroeconomic model representing the economic relationship between sectors and regions to assess the propagation of direct economic impacts through the economic value chain.
Note: Scenarios were defined to reflect possible extreme events to occur by 2050 and 2100 (adverse scenario). 1921 was chosen as a reference as it marks an historic, observed drought that has been considered as plausible to re-occur by experts by 2050/2100 (Boé et al., 2018[15]) in both the RCP 4.5 and RCP 8.5 climate change projections. In addition, it is one of the only scenarios for which data considering historic drought impacts on reservoir lakes exist. As no data on the soil moisture levels in the 1921 drought exist, estimations of extreme soil moisture levels were used based on levels observed in the 1976 drought. Finally, the groundwater levels are projected as an extrapolation of the decreasing trends observed in 2020 to 2022 (last available data), showing a 6% drop in elevation compared to 2020. The temperature of surface waters is defined as the median temperature profile from a multi-year model of the Seine River's water temperature under an RCP8.5 scenario. The median scenario aims at isolating the effect of the water temperature. The adverse scenario considers that drought trends may worsen over time.
Source: Authors based on modelling from (Boé et al., 2018[15]).
Building on these scenarios, it is estimated that a severe drought occurring in the Paris metropolitan area could cost up to EUR 2.5 billion. Direct costs, stemming from water use restrictions induced by low river flows and low levels of aquifers, as well as losses resulting from low soil moisture, would range from EUR 966 to 1446 million, and represent up to 70% of the total cost for the region (Table 1.3). For each of the scenarios, almost half of the costs would be borne by the manufacturing sectors due to water use restrictions that would be imposed under the drought event. The costs borne by the agricultural sector are estimated up to EUR 220 million linked to irrigation restrictions, and up to EUR 146 million due to soil droughts both leading to production losses. Disruptions in energy production due to higher water temperatures represent a value-added cost of EUR 24 million in 2050 and 50 million in 2100. Finally, beyond water use restrictions, soil droughts induce the phenomenon of clay shrinkage, which is responsible for structural damage to buildings, estimated at around EUR 300 million for each of the scenarios. Due to data and methodological constrains, the analysis excluded the impact of water shortages on the health and sustainability of ecosystems. The baseline scenario compares to the damages incurred by France following the significant flood of 2016 (EUR 1.4 billion (Fédération française de l'assurance, 2017[18])), considered the worst since 1982. In the adverse scenario, the total costs for the region compares to the costs of the storm Xynthia (EUR 2.5 billion (Association française de l'assurance, 2011[19])) that hit France in 2010 and is one of the worst natural disasters experienced in the country in the past decades.
Droughts have economic ripple effects as changes in production and the demand cascade through the economic value chains. While some activities, such as road transportation, distribution of goods and banking may not be directly affected by drought conditions, they indirectly suffer economic losses due to decrease in their suppliers or clients’ activity. Similarly, economic disruptions spread along the value chain to economic actors located outside of the Paris metropolitan area and could be felt in the rest of France and other European regions. These additional economic costs are estimated to reach between EUR 200 to 330 million for other French regions, and up to 170 million for EU countries.
EUR millions
Note: The costs represent the losses in added value in euros of 2020. The total costs account for the direct and indirect costs.
Source: Authors.
Droughts also have social and environmental impacts that go well-beyond their economic consequences. Water use restrictions for domestic and recreational use impact citizens’ well-being. In addition, droughts reduce the dilution of chemicals (e.g. nitrogen and phosphorus from agriculture and sanitation discharges) and organic compounds in water bodies, threatening ecosystem health. Increased pollution or temperature in water bodies due to lower water levels can lead to a lack of oxygen and higher water toxicity. This, in turn, threatens the good ecological status of water bodies, their aquatic biodiversity, and the suitability of water for drinking and recreational uses (e.g. swimming). Droughts can also degrade green infrastructure in cities, such as parks and gardens that play a vital role in mitigating heat islands and regulating rainwater contributing to the health of citizens. Resources allocation during water shortages period may also cause tensions with other water users in the catchments beyond the Paris metropolitan area or between urban users and other users in the catchment, such as agricultural users, especially as the city of Paris sources some of its drinking water from locations outside the Paris metropolitan area.
1.2.1. Strategies to address water scarcity risks induced by droughts have significatively improved
All major national strategic plans have recognised droughts as a strategic risk and policy priority. Drought risk has been strongly recognised in France’s first National Adaptation Plans, giving rise to the first national drought risk assessment (Explore 2070). The second National Adaptation Plan in 2018 led to the elaboration of the first National Strategy to Adapt Water Resources to Climate Change (Ministère de la Transition Ecologique et de la Cohésion des Territoires, 2018[20]),a multi-stakeholder agreement aimed at improving the use of water resources through increased water conservation and efficiency, improved water allocation, the mobilisation of unconventional resources, and better water quality. It reinforced the need to align urban planning with the river basins’ management plans. Similarly, the 2023 National Water Plan encourages a reduction of water withdrawals by 10% by 2030, promoting preventive action such as water conservation, resource use efficiency and the integration of unconventional water resources (such as rainwater harvesting).
At the regional level, strategic policy documents recognise the importance of drought risk management. The Climate Adaptation Strategy of the Seine-Normandy basin provides drought hazard projections and proposes a set of preventive measures to build resilience to water scarcity. Building on this strategy, the Paris metropolitan area released a Climate Change Adaptation plan in 2022 (Région Ile-de-France, 2022[21]) which recognises drought as a risk for the region’s-built assets and ecosystems. Drought risk prevention is at the core of this strategy. Similarly, the Greater Paris Metropolitan Area elaborated its Metropolitan Climate Air Energy Plan in 2018, highlighting the vulnerability of houses to droughts due to clay swelling and envisaging to improve knowledge related to droughts’ impacts on ecosystems and assets at metropolitan level (Métropole du Grand Paris, 2018[22]). While the city of Paris’ resilience strategy already identified drought as a major risk, its forthcoming Climate Plan (2024-2030) recognises water scarcity risks prominently, setting out ambitious objectives to mitigate such risks and reduce vulnerability to it. The plan suggests reducing water withdrawals for potable water by 15% reduction in water withdrawals for drinking water by 2030 and to optimise the management of unconventional water resources such as rainwater or even swimming pools ’ones (Ville de Paris, 2023[23]).
1.2.2. Current strategies do not reflect a long-term vision anchored in drought risk assessment
Common to all strategies is the absence of a long-term strategic vision, reflecting insufficient drought risk knowledge. The investments and behavioural changes required in the use and management of water resources under climate change necessitate long-term planning and vision. However, no strategy goes beyond 2030. This is partly due to the absence of drought risk assessments that integrate climate change scenarios. Currently, there is no assessment to determine whether future water supply would be enough to meet water demand in the long-term. As a consequence, the water utilities, the agency responsible to manage river ways or any institution depending on water resources do not know whether and how they will be exposed or vulnerable to droughts in the future. For such assessments, quantitative, spatial, and temporal information of water demand is needed. Efforts are underway to enhance knowledge of climate-induced drought risks, with a new programme (i.e. Explore 2) aimed at providing updated hydrological projection data to perform risk assessment.
The strategies may fall short of achieving resilience to water scarcity. At national and river basin levels, the objectives laid out to ensure resilience consist in reducing water withdrawals by 10%, optimising resources and improving water quality. While standards of water quality exist, it is unclear whether it will be enough to ensure water availability considering future dilution capacity of water resources in the event of droughts. In addition, while strategies to preserve water quality have been implemented for decades, the water quality has not improved as expected (Agence de l'eau Seine Normandie, 2019[24]) casting doubts on the measures proposed. Similarly, if reducing water withdrawals by 10% at river basin level will reduce vulnerability to droughts, such objective is not derived from a risk assessment and does not correspond to any targeted level of resilience. Hence, despite such a reduction in water withdrawals, the region may still suffer drought restrictions in the case of a drought like the 1921 one. In addition, considering business as usual scenarios such as those used for the assessment of economic costs above, the targeted reduction of withdrawals laid out in the strategies appear as extremely challenging. The extent to which national and regional stakeholders are willing to accept drought restrictions, i.e. the acceptable social and economic costs that the region accepts to incur in various drought scenarios is not addressed in the various plans and strategies described above.
1.2.3. Despite an integrated water governance framework, further sectoral coordination is needed to foster policy alignment
Despite cross-sectoral governance that embraces a whole-of-society approach to managing water resources, sectoral coordination remains a challenge. The water governance prevailing in France is consistent with fostering resilience to droughts. It recognises the role of all the sectors and public stakeholders in water management, who all rely on water resources. Despite this and for example, the agricultural sector largely neglects droughts, even promoting practices contradictory to water preservation (Cour des comptes européenne, 2021[25]). At the regional level, agricultural policies and the stated ambition to strengthen food security (Région Ile-de-France, 2021[26]) could increase irrigation water needs by 45% by 2050. While the Paris metropolitan area, including the City of Paris, are considering greening mobility and clean energy strategies, they do not seem to adequately assess the risks of water scarcity. For instance, cooling network installations to foster green air conditioning are dependent on resources from the Seine River for 70% of the energy produced. Strengthening cooling network installations to foster green air conditioning could be incompatible with tackling future droughts (Ville de Paris, 2019[27]).
In addition, the region could benefit from further upstream-downstream coordination, especially between urban and peri-urban areas within the Seine-Normandy river basin. All regional strategies and plans align with the national Water Plan's ambition to strengthen prevention of water scarcity, though there are some differences based on the mandates of regional stakeholders. Regional administrations, for example, oversee environmental and economic development policies, and hence focus their efforts more on biodiversity protection than water supply, which is managed at the municipal level. Since all local governments are responsible for urban planning, it is important that water management objectives set out at the basin level are integrated in a coordinated manner. For example, improving water quality is one objective where decisions made by upstream municipalities affect downstream ones, regardless of their individual plans. Similarly, national and river basin strategies aim to reduce water withdrawals by 10% at the river basin level which in turn requires coordination to determine how each municipality needs to contribute to this objective while considering upstream-downstream cooperation. Currently, there are no coordination mechanisms to ensure that regional strategic documents complement each other, maintain consistency in urban planning, facilitate upstream-downstream cooperation, and prioritise actions within the region.
Building resilience to drought-induced water scarcity requires a combination of measures to manage both water demand and supply, as well as improve water quality. Water demand measures aim at conserving water or improving water efficiency (e.g. awareness raising campaigns to promote shifts in water usage patterns, water allocation mechanisms...). Water supply measures aim at improving water supply efficiency or providing additional resources, others than through withdrawals. Lastly, improving water quality helps mitigating water scarcity risks induced by lower dilution capacity of aquatic environment that could create pollution issues rendering activities such as swimming, potable water production or reproduction of fish species challenging, among others.
1.3.1. Reducing water withdrawals reduces drought-induced water scarcity risks
The region has successfully managed to reduce water withdrawals in the past. To date, total volumes of water withdrawals have decreased by 14% since 2012 (Figure 1.5). The demand for drinking water decreased by 8% between 1998 and 2008, with significant disparities between Paris (-32%) and the more rural part of the Paris metropolitan area that experienced an increase in consumption (Agreste, 2011[28]). With 123 litres person per day, household water consumption in the region is now below the French average and relatively low compared to other OECD countries. The decline of major steel and chemical industries in the region (Chevrot et al., 2018[29]) led to an average annual reduction of 14% in industrial water withdrawals from 2015 to 2022. Conversely, irrigated areas (7%) increase (Agreste, 2022[30]), resulting in a doubling of irrigation withdrawals between 2012 and 2020.
Volumes abstracted annually from 2012 to 2020 (m3)
Source: Authors based on the national database of water withdrawals (BNPE).
The objectives of the National Water Plan to further reduce water withdrawals may be very ambitious considering current consumption patterns. Translating the National Water Plan’s goal of a 10% reduction in water withdrawals into sector-specific targets requires reducing potable water withdrawals to be reduced by 14% by 2030 compared to 2022, a rate that significantly exceeds past trends (Agence de l'Eau Seine Normandie, 2023[16]). Water abstraction for the industry sector is expected to reduce by 4% at a time where France ambitions to reindustrialise the country. Finally, water abstractions for irrigation are to remain constant which might be challenging as climate change and food security policies are expected to increase needs in a sector where water uses are marginal currently (Figure 1.6).
Note: The share of abstractions for irrigation excludes energy and canals uses.
Source: Authors based on data from BNPE.
1.3.2. Demand-side measures have successfully contributed to reducing water withdrawals, but there remains untapped potential
Measures to raise awareness could be scaled up
Measures to raise awareness should focus on reducing water consumption in the long term. Drought risk monitoring services, such as VigiEau2 were created to monitor and communicate about drought preparedness measures. The French Ministry of Environment has developed communication kits “Chaque geste compte, préservons nos ressources” (“Every action counts to save resources”) to support local stakeholders and water utilities in their efforts to raise drought risk awareness and increase knowledge on how to reduce water consumption.3 However, these measures have focused on crisis anticipation and management. Other measures, such as water-saving labels for household appliances should be expanded to inform conscious consumption choices. This measure could reduce household water consumption in the region by 22% (Ademe, 2021[31]) and stimulate further innovation in products’ design. Measures to train farmers to use water-efficient crops, such as the “Enseigner à produire autrement” (Teaching to Produce Differently) programme are promising avenues to further reduce water abstraction rates in the future.
Water prices do not reflect scarcity, but an increase may not be effective and can prove challenging
Potable water prices in the Paris metropolitan area are low and do not reflect the scarcity of water. Overall, the share of households’ consumption expenditures for water in France is relatively low, and half of many other European countries (Figure 1.7). The cost of drinking water varies across the Paris metropolitan area, with notably low prices in the inner city of Paris and rates above the French national average in other cities of the region. Current consumer prices for potable water are based on cost recovery of water operators but were not set to reflect water scarcity.
%, Average on the period 2018-2022
Source: Authors based on Eurostat data. The total households’ expenditures cover 12 categories of expenditures such as recreation, transport, health, education, furnishing, housing (including water and energy), beverages and other goods and services expenditures.
Despite relatively low water prices for potable water, an increase is unlikely to yield water savings. Given that the region is characterised by a predominantly urban population with already below-average water consumption levels, increasing water prices may not be effective in reducing demand for drinking water. In addition, the water tariffs are the lowest in the wealthiest departments of the region. Hence, when there is room for significant increase, this is also where the price elasticity is theoretically the lowest (Figure 1.8). Finally, metering, which could enable households to better understand their consumption and become more responsive to pricing, remains uncommon in the region.
Note: Each dot represents a department of the Paris metropolitan area.
Source: Authors based on data from INSEE and SISPEA.
Water prices for agriculture and manufacturing do not reflect water scarcity either but increasing them can prove challenging. Prices for irrigation are higher in the Paris metropolitan area than in other French river basins (Figure 1.9), except for gravity-fed irrigation, which is a marginal practice in the region. Nevertheless, water prices remain too low to encourage farmers to switch to less water-intensive crops or reducing the area under irrigation. In the manufacturing sector, prices are not set to incentivise water conservation or efficiency. Yet, increasing prices in the agriculture sector would require significant increase to influence water demand and pose acceptability challenges (up to tenfold).
0.01 EUR/m3, 2022
Source: Authors from data of the various water agencies.
Water allocation mechanisms have been used to limit water use only during drought crisis management
The water allocation regime prevailing in the Paris metropolitan area barely limits abstractions except during drought crises. Generally, water in the Seine-Normandy Basin is allocated for long period of times, with no restrictions if the user can demonstrate that there will be no negative impact on resources and ecosystems based on an environmental evaluation.4 Restrictions only come into play during droughts. Departmental drought Decrees (Ministry of Environment, 2023[32]) then regulate water allocation by priority uses. They define a system of gradual restrictions ranging from awareness-raising to abstraction bans, with a view to prevent potable water scarcity and ecosystem damages. This could lead to, for instance, the agriculture sector to be asked to reduce withdrawals by up to 50% to save water, while citizens will not suffer any restrictions for potable water use.
Promising initiatives are underway at both regional and national levels that promote long term reductions in water abstraction. Aqui’brie, for example, is an association that manages an aquifer providing drinking water to nearly 10% of the region’s citizens and water for irrigation and manufacturing. As the aquifer’s water levels were decreasing, this association was set up to propose a joint and sustainable management of abstractions informed by scientific models and bringing users from water utilities, the agriculture and industry sectors together to collectively reduce water abstraction consistently over time. At the national level, recent regulations have been developed to incentivise companies to reduce water consumption by lessening their water restrictions during drought conditions. Finally, the national level initiative encourages water sharing mechanisms through farmers associations (Organismes Uniques de Gestion Collective) or more recently collaborative territorial projects (“Projets de Territoire de Gestion de l’Eau”). The farmers association can distribute water withdrawal rights based on its own allocation criteria (Cinotti, Galtier and Granger, 2020[33]). In the case of territorial projects, water users need to demonstrate that they consider climate impacts in their water consumption trajectories.
Faced with demanding irrigation goals, significant efforts are needed to allocate existing water permits sustainably in the agriculture sector. While the sector is expected to keep irrigation volumes constant, the Paris metropolitan area plans on increasing food security (Région Ile-de-France, 2021[26]), suggesting increased irrigation needs. In addition, as climatic conditions might worsen, irrigation needs might also increase. Hence, when water withdrawals permits are shared among farmers through a farming association, this association could promote a system that rewards those who adopt practices conducive to water conservation and resource optimisation, or that support long-term reduction of water withdrawals. Similarly, long-term water conservation trajectories could be required in water permits’ applications. Finally, drought restrictions can further be adapted to incentivise users to reduce water consumption in the first place. This entails moving away from a static model of water allocation towards one that incentivises virtuous behaviours, thereby fostering a culture of innovation and resilience within the agricultural sector.
There is room for a higher adoption rate of household water savings equipment
Despite the potential benefits of water-saving technologies, their adoption rates remain limited in the Paris metropolitan area. For example, initiatives such as distributing water-saving kits aim to reduce potable water consumption (such as faucet devices) without compromising user comfort. Although these technologies offer estimated water savings of around 10% on average (Ville de Paris, 2013[34]) their adoption rates remain limited in the region. One cited reason is the lack of sustainability of these solutions, as users may not renew their equipment or simply not to install it. This suggests a need for increased awareness and the implementation of financial or regulatory incentives to promote the adoption of these technologies.
1.3.3. Continued investment in water supply measures will be an important element of future drought resilience
While riverine infrastructure has significatively contributed to the resilience of the region, worsening drought trends may compromise their efficiency
The Paris metropolitan area is endowed with a robust riverine infrastructure network that plays a crucial role in ensuring adequate water flow and levels in major rivers. The region benefits from four reservoir lakes that provide an important water storage capacity. Through regulating water flows and levels, they help secure water supply for potable, industrial, agricultural, and energy production uses during water scarce periods. They also play an important role in managing flood risk (OECD, 2014[35]). The volumetric capacity of the lakes represents 71% of the annual water withdrawals in the Paris metropolitan area. The water stored is then released from June until end of October each year, contributing up to 70% of the river flows during summers (AESN&DRIEE, 2016[36]). Mobile dams installed along rivers allow for the regulation of water levels throughout the year, ensuring river navigation while also managing flood risks during heavy rainfall periods. Based on the OECD scenarios, even in adverse drought scenario, water flow rates will be sufficient to maintain water levels for navigation on the Seine, suggesting significant resilience of the fluvial transportation sector to water scarcity.
Using the reservoir lakes to manage both the increased drought as well as pronounced flood risk is a challenge. Until recently the reservoir lakes have been mostly concerned with managing flood risks throughout the year, which pursued a strategy of releasing excess water intermittently and using the storage capacity to attenuate flood risk levels during heavy rainfall. The agency managing the reservoirs (Établissement Publique Territorial du Bassin EPTB) is increasingly aware of the need to manage the lakes with a view to increasing water storage capacity for the event of droughts. However, with an increased flood risk during winter, allowing for longer-term water storage to ensure summer drought support entails an important trade-off. Creating new lake infrastructure to add storage capacity was ruled out as an effective drought management measure, echoing concerns about being able to fill the reservoirs in the first place.
Drinking water supply relies on robust distribution networks and strategies
Drinking water infrastructure is resilient to droughts. The average network water losses for the region stands at approximately 10% (SISPEA, 2021[37]), surpassing both the French national average (20%) and European levels (23%) (EurEau, 2021[38]). Water operators are deeply committed to maintaining and enhancing this performance, making significant investments to that extent. Furthermore, water operators have established interconnections to ensure mutual support during drought events (Aquavesc, SEDIF, Sénéo, Ville de Paris, 2020[39]). Among these operators, the Paris drinking water authority (Eau de Paris) benefits from diverse underground water resources, outside of the region, and stores everyday twice the needs for potable water in Paris.
While the performance of public water distribution networks is generally excellent, disparities exist between municipalities and more could be done on private networks. Leak alert systems deployed by water utilities in the region on private networks have demonstrated that significant savings are possible. Increasing such measures could represent significant water savings and reduce water bills for households, companies or public administrations. In addition, while public networks’ performance is generally excellent, disparities exist between municipalities. with some older and less well-maintained piping systems in some rural areas. Hence, while the 4 distribution networks in the interconnected area demonstrate higher than 90% performance ratio, 25% of the municipal networks have performance ratio below 77% and hence below the French average (Figure 1.10). Improving the performance of these networks by 10% can contribute to significant water savings (nearly 12% of the water savings efforts required by the national water plan).
Ratio of volumes consumed over volumes distributed for municipalities within the region, France and for European countries in 2021
Note: The average performance of municipal distribution networks in the region is lower than the average performance for the region. This is explained by the calculation method, as the average performance for the region reflects the ratio of the total volumes consumed in the region over the total volumes distributed. The data provided in this figure gives equal weight to distribution networks of small rural areas and those of the interconnected area, hence the average performance of municipal distribution networks in the region is lower.
Source: Authors, based on SISPEA data.
Nature-based solutions are progressing, but their uptake requires further knowledge
Nature-based solutions contributing to water retention are gradually being implemented in the Paris metropolitan area. The protection of wetlands and forests areas can increase water storage capacity by improving soil moisture and aquifer recharge and can avoid water run-off (Office francais pour la biodiversité, 2012[40]). In cities, revegetation or de-sealing can significantly reduce the urban heat island effect, thereby limiting the increase in drinking water consumption observed during heatwaves. Biodiversity restoration, including wetland protection, afforestation and green urban infrastructure are among the priority measures implemented by the Seine-Normandy water agency (Agence de l'Eau Seine Normandie, 2022[41]). A programme envisages to protect 1000 hectares of urban abandoned land by 2025, and to accompany the planting of 2 million trees by 2030 (Région Ile-de-France, 2022[42]). Similarly, the Greater Paris Metropolitan Area authority has established a biodiversity fund to finance tree planting operations, ecological gap filling, and the de-sealing and renaturation of spaces with ambitious goals. The Greater Paris Metropolitan Area authority also promotes innovative solutions for integrating these solutions into urban planning through calls for projects. Finally, the city of Paris elaborated a biodiversity strategy aimed at reducing water evaporation rates and water needs for vegetation by consistent species selections. The strategy also emphasises the importance of de-sealing (Ville de Paris, 2018[43]).
To exploit the full potential of nature-based solutions, the mapping of ecosystems and their services is needed. Studies have been conducted to assess the potential for de-sealing public spaces in the city of Paris to increase natural groundwater storage capacity (APUR, 2023[44]). Considering the costs of de-sealing, priority should be given to areas where storage will effectively mitigate drought risks, i.e. in locations where infiltration can indeed lead to increase storage. Similar studies are conducted to evaluate opportunities for renaturing watercourses and wetlands. However, barely 10% of wetlands are currently mapped and therefore eligible for protection (DRIEAT, 2020[45]). Knowing the status of buffer zones would allow for the identification of priority areas to be preserved, as they have the greatest water storage capacity and therefore support during low-flow periods in the summer. A river basin-wide analysis could further support the identification of areas to strategically invest in Nature-based solutions to generate water security benefits.
Unconventional water supply measures hold a significant potential to contributing to water use efficiency
Water reuse measures are increasingly considered in the region. The Seine-Normandy water agency finances projects aimed at reusing wastewater in closed-loop systems to reduce industrial water withdrawals or meet the energy needs of infrastructure. With the current pressure to reindustrialise the country, water reuse will be particularly important. Similarly, the use of rainwater is permitted for all outdoor purposes, toilet flushing, floor washing, and laundry in the region. The regional authority offers 50% support to individuals wishing to install water collectors for sanitary use or garden watering (Région Ile-de-France, 2022[46]). The City of Paris informs citizens about the possibility of rainwater collection, especially for watering shared gardens or vegetation. It also requires real estate developers to install rainwater collectors for watering associated building spaces and for sanitary purposes. Additionally, projects for reusing drainage or pool water have been initiated in the region and are undergoing detailed studies. The potential volume of swimming pools’ waters in Paris alone could represent 16% of the non-potable water volumes used by the city (APUR, 2022[47]). However, reclaimed water or greywater infrastructure are not used in the Paris metropolitan area.
The adoption of water reuse measures could constitute an interesting option for new buildings, depending on their cost-efficiency. The installation of rainwater harvesting systems to store and reuse such resources can be complex and costly for existing buildings, which has hindered their adoption. In new constructions, especially in less dense areas rainwater collection can be easily integrated in water and sanitation infrastructure. Regarding pool water and mine water, cost-benefit ratios vary depending on the final uses and deploying infrastructure to use such resources requires a case-by-case analysis as those provided by the Parisian Urban Planning Agency (APUR) (APUR, 2013[48]). Finally, while reclaimed water is probably not adapted to households, it could prove suitable for irrigation.
Addressing regulatory challenges may foster the implementation of water reuse measures. Current regulations, particularly regarding greywater reuse, limit investments in improving associated technologies. Greywater reuse currently falls under treated wastewater regulations, limiting its use to irrigation and watering of green spaces, subject to adequate treatment, mostly for health considerations. Therefore, despite examples from Spain and Japan demonstrating the potential of greywater to conserve household water traditionally used for sanitation, it cannot currently be incorporated into private construction plans. This restriction also applies to rainwater reuse, as existing regulatory frameworks provide minimal guidance or support. In 2022, legislation was amended to streamline procedures and facilitate wastewater reuse by eliminating regulatory hurdles such as assessments, authorisation processes, and specific wastewater quality standards under certain conditions. Additional efforts are needed to promote broader adoption of water reuse practices.
In implementing water reuse measures, it is crucial to avoid inadvertently creating maladaptation. Grey infrastructure geared towards fostering water reuse is often touted as effective in mitigating drought risks, drawing inspiration from practices worldwide. However, water reuse could negatively impact the Seine River flows as the discharge of treated wastewater can contribute up to 70% to the flow of the river during low water periods. Hence, diverting this water for reuse could significantly reduce the river's flow.
Beyond water reuse, other unconventional resources may be considered but with a significant risk of maladaptation. While water reservoirs are seen as a way to mitigate drought risks, they can also negatively impact water resources and the environment by reducing river and seasonal low flows (Carluer N., 2017[49]). The Seine-Normandy water agency takes a cautious approach, approving such infrastructure only in specific cases and where long-term reduction in water withdrawals can be demonstrated. This careful strategy helps prevent increased water dependency and in turn vulnerability to water scarcity, as well as potential maladaptation. Similar risks exist with water transfers between river basins.
1.3.4. Water quality measures have not met their goals
Ensuring water quality is an essential element of adapting to future droughts. The quality of water resources in the Paris metropolitan area is threatened by diffuse pollution from agricultural activities, including nitrogen, phosphorus, and pesticides, as well as pollution from urban areas. Measures such as regulations governing water pollution levels or financial incentives to support sustainable farming practices are essential to prevent water scarcity induced by lower dilution capacity in case of droughts. However, regardless of climate impacts, current measures have proved insufficient to ensure water quality on the river basin, with 41% of the surface water and 30% of underground water resources deemed as good quality in 2019 (Agence de l'Eau Seine Normandie, 2022[41]) and even worse results in the Paris metropolitan area (Figure 1.11).
2019
Source: (DRIEAT, 2019[50]).
1.3.5. Drought resilience measures must be adapted to the types of water users
Understanding the profiles of water users is important to tailor effective drought resilience measures. Considering the ambitious overall water reduction goal the region set out to meet, all types of water users will have to contribute proportionally to their capacities. For measures to be effectively adopted it is therefore important to carefully assess the level of effort that can be expected from each user, which depends, among others, on the water reduction efforts already undertaken in the past, but also on the needs and current consumption of users. For example, faced with increasing needs induced by climatic conditions and food security strategies in the region, the agriculture sector may not be able to keep irrigation withdrawals constant by 2030 set by the Seine-Normandy water agency. To cope with future water demand in the sector while keeping constant irrigation withdrawals compared to 2022, the agriculture sector may then need to integrate water reuse for part of the irrigation’s needs, water efficient equipment and to consider changing crops or reducing irrigated areas to conserve water.
However, comprehensive knowledge of water consumption patterns by user type remains limited in the Paris metropolitan area. Currently, there is no data of existing consumption by type of water user as there is no individual metering services in the region. Most studies conducted reflect a very specific perimeter of domestic users and do not reflect the diversity of drinking water uses (e.g. administrations, companies, hotels, rural and urban citizens...). While overall volumes consumed are known annually, no granular data exist to assess the effective uses of farmers and industries. Finally, withdrawals under a certain volume are not reported at all.
The region lacks a financing strategy reflecting an assessment of the needs to build resilience against droughts. The absence of a specific resilience target makes it challenging to accurately determine financial requirements. However, the action plan within the water plan indicates a necessity for increased public funding, alongside efforts to attract private investment, highlighting the need for a collective financial effort. Furthermore, while reduced water consumption benefits conservation efforts, it jeopardises the financial stability of water agencies and operators who rely on these tariffs. These revenues are crucial for funding infrastructure upgrades and resilience initiatives. Similarly, financial compensation schemes such as national catastrophe insurance (CatNat), which cover damage from building due to drought trends, face sustainability challenges.
Confronted with financing needs, it is crucial to identify funding sources. These sources could either come from existing funds or new avenues. First, integrating drought risks into existing funds like the national Major Natural Risk Prevention Fund and Green Fund could enhance synergies between flood prevention and drought resilience efforts, providing significant co-benefits. Indeed, financing measures for drought resilience could help mitigate flood risks. Additionally, aligning financial instruments such as the European agricultural funds with sustainable water practices could efficiently allocate resources to support drought resilience. Finally, exploring new revenue streams, such as payments for ecosystem services, increasing volumetric water tariffs, introducing fixed charges for resilience, or imposing fees for water pollution, could strengthen financial resilience against drought risks. Moreover, to supplement additional resources, encouraging private sector investment in drought resilience is crucial, promoting a culture of managing water-related risks.
Drought risk assessment
Improve monitoring of water uses and abstraction volumes by type of user in the region to better understand water demand and its impact on the availability of water resources.
Update water supply projections at regional level to integrate recent climate change projections.
Project water demand in different socio-economic scenarios.
Identify economic and non-economic activities exposed to drought risk under changing climatic conditions and assess their vulnerability at regional level (e.g. river flow under which fluvial transportation is threatened, or soil moisture levels leading to crop losses...).
Define an acceptable level of risk based on the vulnerability analysis (e.g. minimum level of river flows to ensure ecosystem functioning or access to drinking water...).
Communicate publicly on the results of the drought risk assessment to raise awareness.
Strategic framework
Reinforce strategies and drought resilience plans by adopting a long-term, cross-sectoral vision, anchored in a thorough drought risk assessment that accommodate uncertainty and remain flexible to reorient action depending on the climate trajectories.
Enhance coordination between municipalities to align water management measures to ensure upstream-downstream solidarity and coordination between urban and peri-urban areas.
Strengthen policy coherence between regional economic development, urban planning, climate change, industrial and agricultural policies, and water management objectives.
Engage stakeholders across all sectors and define accountabilities and actions for all in the drought resilience plans.
Demand-side measures
Pursue information and awareness-raising efforts that encourage the adoption of water savings measures by all types of users such as changes of crops, households’ behaviours including outside drought periods.
Promote the use of water efficient technologies such as water saving kits for households or efficient irrigation equipment.
Use existing water allocation mechanisms such as water permits or waivers for drought restrictions to incentivise long-term reduction of water withdrawal.
Promote collaborative experience such as Aqui’brie or farmers’ associations as ways to achieve long-term water abstraction reductions.
Water supply measures
To optimise the selection of water supply measures, conduct a water consumption diagnosis to evaluate the need to complement water conservation measures by water supply ones.
Continue efforts to improve water network efficiency, especially at the municipal level.
Systematically monitor leakages in private networks to encourage water savings in households, administrations, or companies.
Consider the adoption and integration of grey water reuse in regulations.
Foster rainwater reuse measures in constructions when relevant.
Ramp up efforts to map ecosystem services to identify priority areas for the deployment of nature-based solutions to increase natural groundwater storage capacity.
Financing resilience to droughts
Develop a financing strategy that assesses the costs of the public investments needed to implement the measures promoted at river basin, regional and municipal levels, as well as funding sources to build resilience to drought.
Better align public investments with drought resilience to strengthen the efficiency of existing funds, such as those of the national Major Natural Risk Prevention Fund and Green Fund, or from public infrastructure operators.
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← 1. Representative Concentration Pathways (RCP) are climate change scenarios to project future greenhouse gas concentrations. There are four RCP scenarios ranging from very high greenhouse gas concentrations (RCP8.5) to very low (RCP2.6).
← 2. The plateform Vigi’Eau is publicly available on vigieau.gouv.fr.
← 3. This plateform proposes messages and tools to support local stakeholders in raising awareness on droughts and water saving measures: https://www.ecologie.gouv.fr/actualites/secheresse-france.
← 4. The environmental evaluation is part of a standardised procedure under the law water that is described on the website of the Paris metropolitan area prefecture region. (Dossiers loi sur l’eau : mode d’emploi | DRIEAT Île-de-France (developpement-durable.gouv.fr))