Toute l'actualitéToday, water deficit is no longer an occasional hazard but a structural transformation of the hydrological cycle. In many agricultural regions, atmospheric demand now exceeds the capacity of ecosystems to retain and redistribute available moisture. This shift challenges a productive model historically built on climatic stability and the relative availability of water resources. How can the continuity of agricultural production be maintained when water becomes a structural limiting factor? Rethinking agricultural models therefore requires revisiting the biophysical mechanisms that govern water infiltration, storage, and availability across soils, crops, and territories, and repositioning the capacity of ecosystems to regulate water at the core of agronomic and territorial decision-making.
Water Deficit: A Systemic Transformation of the Agricultural Water Cycle
The Intensification of Climatic Constraints
The sixth assessment report of the IPCC highlights the increasing frequency and intensity of agricultural droughts as a combined consequence of global warming and changes in atmospheric circulation. Rising temperatures increase potential evapotranspiration—that is, the amount of water that could be transferred from soil and plants to the atmosphere if water were available without limitation. This indicator reflects climatic water demand: the warmer, drier, and windier the air, the greater this demand becomes. Consequently, even when precipitation remains constant, an increase in potential evapotranspiration intensifies crop water stress, as the atmosphere demands more water than the soil–plant system can supply.
Water stress therefore arises from a structural imbalance between the actual supply of water—dependent on rainfall and the soil’s capacity to store it—and a rapidly increasing atmospheric demand. This tension alters cropping calendars, weakens sensitive phenological stages such as flowering or grain filling, and increases the variability of yields from one year to the next. In this context, productive stability becomes a central concern: a system’s capacity to absorb successive water shocks now determines economic viability as much as the yield levels achieved in favorable years.
Blue Water and Green Water: A Strategic Framework
The work of Malin Falkenmark beginning in the mid-1990s, followed by research conducted with Johan Rockström in the early 2000s, profoundly reshaped hydrological analysis by distinguishing between blue water stored in rivers and aquifers and green water retained in soils and directly used by plants.
Rainfed agriculture—that is, production systems relying exclusively on natural precipitation rather than artificial irrigation—accounts for the majority of cultivated land worldwide. It depends directly on the moisture stored in soils following rainfall infiltration, in other words on green water. The hydrological performance of rainfed agriculture therefore depends on the soil’s ability to absorb precipitation, slow runoff, build a usable reserve within its active horizons, and release this water in line with the physiological needs of crops.
Water deficit thus reflects a failure of ecosystem regulation as much as a volumetric shortage. Such a perspective shifts attention toward the structural and biological quality of soils, as well as the spatial organization of agricultural landscapes, which determine how water circulates and how long it remains within territories.
From Water Deficit to Water Bankruptcy
When these natural regulatory mechanisms deteriorate over time, a structural imbalance can emerge between needs and ecological capacity. At the scale of territories and value chains, such an imbalance corresponds to what the United Nations University report Global Water Bankruptcy describes as water bankruptcy: a tipping point at which water demand permanently exceeds the capacity of ecosystems to supply it, jeopardizing agricultural production, supply security, and the economic stability of entire sectors.
Toward Water Sobriety: Restoring the Hydrological Capacity of Soils
Vegetative Cover and Infiltration Dynamics
In agricultural systems, soils left bare between crops exhibit structural vulnerability to intense rainfall. The kinetic impact of raindrops breaks down surface aggregates; disaggregated silts and clays migrate toward the surface and clog soil pores—that is, the interstitial spaces through which water infiltrates and circulates—forming a surface crust that reduces infiltration capacity. Excess water then runs off across the surface, carrying away fine particles and nutrients while the replenishment of the soil’s plant-available water reserve remains limited.
Introducing cover crops fundamentally alters this sequence. Vegetative cover absorbs the impact of raindrops, root systems structure the soil at depth, and associated biological activity—earthworms, microorganisms, and root exudates—fosters the formation of stable aggregates. This biological architecture increases macroporosity, improves hydraulic continuity, and facilitates percolation toward active soil horizons.
Several meta-analyses conducted in temperate and Mediterranean agricultural systems—notably Basche & DeLonge (2017) and Blanco-Canqui et al. (2015)—demonstrate significant improvements in infiltration rates and reductions in runoff in most of the contexts studied, although results depend on climate, soil texture, and crop rotations. The magnitude of benefits therefore varies according to local conditions, requiring a contextualized agronomic approach. When coherently integrated into cropping systems, permanent soil cover increases the share of precipitation effectively stored in the soil and available for subsequent crops, transforming rainfall events into hydrological capital rather than transient flows.
Soil Organic Matter and Water Retention
Soil organic carbon content is a key determinant of the structural architecture of agricultural soils. By promoting the formation and stabilization of aggregates, it directly influences the distribution and continuity of soil pores, and therefore the way water circulates and is stored within the soil profile. Studies such as Rawls et al. (2003) and Minasny & McBratney (2018) highlight a positive relationship between soil organic carbon and water-holding capacity, while emphasizing the context-dependent nature of this effect. Its magnitude depends strongly on soil texture and mineralogy: the impact is generally more pronounced in sandy or loamy soils, where biological structuring compensates for limited intrinsic storage capacity, than in clay-rich soils already characterized by high microporosity.
Increasing soil organic carbon stocks can therefore enhance the plant-available water reserve while improving structural cohesion and reducing vulnerability to erosion. Biological activity stimulated by this enrichment contributes to the formation of macropores and to improved hydraulic continuity within the soil profile. This more functional soil structure strengthens the soil’s capacity to buffer short- to medium-term water deficits, whose frequency is increasing in many temperate regions. In this sense, restoring soil carbon stocks emerges as both a hydrological and climatic lever, stabilizing production while contributing to emission mitigation.
Conservation Agriculture and Hydraulic Continuity
Systems combining reduced soil disturbance, permanent soil cover, and diversified crop rotations profoundly reshape the pore architecture of surface horizons. No-till practices limit the mechanical disruption of aggregates, vegetative cover protects the soil surface and contributes carbon inputs, while diversified rotations encourage differentiated root structuring. Analyses of conservation agriculture systems, including Pittelkow et al. (2015) and Blanco-Canqui & Ruis (2018), show significant improvements in infiltration and structural stability when these practices are implemented together. By contrast, the effects are more variable—and sometimes limited—when no-till is adopted without cover crops or crop diversification, highlighting the systemic nature of the approach.
Improved hydraulic continuity—that is, effective connectivity between soil pores—allows infiltrated water to percolate into deeper horizons rather than flowing across the surface, thereby reducing runoff losses. This structured pore network regulates hydrological flows by absorbing intense rainfall, facilitating water storage within the soil profile, and gradually releasing moisture during dry periods.
Hydrological performance therefore depends on the overall coherence of the cropping system: it results from the integration of multiple practices implemented together rather than from the isolated adoption of a single technique.
Trees and Landscapes: Reconfiguring Agricultural Hydrology
Agroforestry and Microclimatic Regulation
Agroforestry reintroduces vertical complexity into simplified agricultural systems—that is, fields dominated by a single vegetation layer, typically consisting of uniform annual crops. Introducing trees creates multiple vegetation strata that alter energy and water exchanges between soil, vegetation, and the atmosphere.
Trees intercept and redistribute solar radiation (radiative fluxes), reducing the energy reaching the soil surface and the crops beneath. This modulation of radiation lowers surface temperatures and limits excessive heating of the crop canopy. It is accompanied by reduced wind speed within the field, which in turn decreases water losses associated with atmospheric turbulence.
These microclimatic modifications attenuate instantaneous evaporative demand—that is, the amount of water the atmosphere can extract at a given moment from soils and plants when air conditions are hot and dry. During heat waves, this reduction in atmospheric demand can limit the intensity of water stress experienced by associated crops.
At the same time, the depth and diversity of tree root systems contribute to structuring the soil at depth and improving its porosity. Agroforestry design—tree density, row orientation, and species selection—determines the balance between competition and complementarity for water and light. Careful ecological design makes it possible to optimize these interactions between trees and crops in order to maximize the hydrological resilience of the ecosystem.
Vertical Hydraulic Redistribution
Deep tree root systems, capable of exploring several meters of soil depending on species and pedological conditions, access water reserves beyond the reach of annual crops. This deep anchoring modifies the vertical distribution of water flows within the soil profile.
Ecohydrological research, from the pioneering observations of Richards & Caldwell (1987) to more recent syntheses by Neumann & Cardon (2012), documents processes of hydraulic redistribution—sometimes referred to as hydraulic lift—through which water absorbed at depth during the day may be released into upper soil layers when these layers become drier than deeper horizons. This moisture gradient allows water to move upward through the root system, particularly at night when reduced transpiration favors the reversal of hydraulic flows. In this way, the root network connects different soil layers and can, depending on moisture contrasts, help maintain residual moisture in surface horizons, benefiting fine roots of the tree itself and, in some contexts, associated crops and soil biological activity.
The magnitude of this process depends on rooting depth and density, soil physical properties, and the availability of water in deeper horizons. It therefore varies according to tree species, agroforestry design, and climatic conditions. By redistributing water vertically, trees actively contribute to regulating the local water cycle and to stabilizing the functioning of the soil–plant–atmosphere system.
Functional Landscapes and Territorial Water Retention
The simplification of agricultural landscapes—the removal of hedgerows, clearing of woodlots, drainage of wetlands, and enlargement of fields—has profoundly altered water circulation at the territorial scale. By removing physical and biological obstacles that once slowed flows, these transformations have accelerated surface runoff and reduced water residence time within watersheds. An increasing share of rainfall therefore rapidly reaches drainage outlets, limiting diffuse infiltration and the gradual recharge of soils and aquifers.
Restoring ecological infrastructures such as hedgerows, grass strips, and wetlands acts simultaneously on several hydrological mechanisms. Vegetated hedgerows and embankments increase landscape roughness, slow runoff, and promote infiltration upstream. Grass strips intercept surface flows, reduce erosion, and enhance local percolation. Wetlands, whether natural or restored, function as hydrological buffers by temporarily storing water during rainfall events and releasing it gradually, thereby smoothing hydrological extremes.
Analyses by the European Commission’s Joint Research Centre highlight the role of Nature-based Solutions in strengthening the hydrological resilience of agricultural territories, notably by increasing water retention time and moderating peak flows. These mechanisms do not replace technical infrastructures, but they alter their operating conditions by reducing flow variability. Managing water deficit therefore extends beyond the scale of individual fields to that of the watershed. Regulating water flows requires coordination among farmers, public authorities, and economic actors. A territory’s ability to retain, infiltrate, and redistribute water thus becomes a collective asset upon which the hydrological stability of farms and value chains depends.
Agronomic and Economic Adaptation to Water Risk: Transforming Production Systems
Reconfiguring Cropping Choices in a Constrained Climate
By modifying the biophysical conditions in which crops develop, restoring the ecological functions of soils and landscapes constitutes a necessary condition for hydrological resilience. Yet the intensification of water deficits also requires a transformation of the very structure of agricultural production.
The choice of species and varieties becomes a strategic parameter. Differences in physiological responses to water stress—rooting depth, stomatal regulation capacity, phenological plasticity—directly influence a crop’s ability to maintain productive potential under constraint. Adapting crop rotations to regional climate projections therefore amounts to a structural repositioning of agricultural systems in relation to their future environmental conditions.
Crop diversification constitutes a second lever. Highly specialized systems concentrate exposure to water risks on a limited number of productions. By contrast, more diversified rotations distribute risks, reduce dependence on water-intensive crops, and enable more precise adjustment of cropping calendars to critical climatic periods identified through data. Transforming production systems therefore requires reconsidering the coherence between regional climate conditions, crop physiology, and the organization of crop rotations.
Embedding the Transition within Value Chains
These agronomic transformations unfold within value chains whose structure strongly influences decisions at the farm level. Introducing new crops, modifying rotations, or reducing dependence on certain productions requires not only technical adjustments but also commercial and contractual adaptations.
The durability of these transitions depends on the capacity of economic actors to integrate water constraints into their sourcing criteria and long-term commitments. When market outlets are secure and risks are shared, producers gain greater room to adapt their systems. Conversely, rigid economic frameworks tend to maintain production models that are increasingly misaligned with emerging climatic realities.
Water risk is therefore not merely an environmental variable; it affects supply continuity, volume stability, and cost predictability. As episodes of tension become more frequent, the ability of value chains to anticipate these dynamics becomes a determining factor in their economic resilience.
Water deficit highlights a now-central interdependence between climate, ecosystems, and agricultural models. A territory’s capacity to produce under constraint depends first and foremost on the functionality of its soils and landscapes: infiltration, storage, and redistribution of water form the physical foundation of productive stability. Yet ecological restoration alone is insufficient without parallel changes in cropping choices and economic frameworks. Aligning production systems with regional climate trajectories and structuring value chains accordingly becomes a condition for long-term viability. Technical infrastructures—irrigation systems, storage facilities, and monitoring tools—can complement these dynamics. Their effectiveness, however, remains closely tied to the hydrological quality of the ecosystems in which they operate. Rethinking agricultural models in the face of water deficit therefore implies a change of scale: from field to watershed, from annual yield to multi-year stability, from water management to the transformation of production systems. The future of agriculture will depend on this articulation between restoring living systems and reorganizing value chains within an increasingly uncertain hydrological regime.