There are critical opportunities and profound challenges at the food–water–energy nexus. Crucial to the global nexus is the role of groundwater. Groundwaters provide 99% of the world’s useable freshwater supplies. Irrigation is required for much of the world’s food production, as 40% of the food grown globally uses irrigation. Yet some 10% of today’s irrigation water is “stolen” from tomorrow, as it relies on today’s use of non-renewable groundwater. With “business-as-usual,” it is predicted we will reach “peak groundwater” around 2050. We review groundwater-protection measures under two contrasting food-production systems: viticulture in temperate New Zealand, and halophyte production for food, fibre, and fuel in the hyper-arid United Arab Emirates (UAE). Some 75% of New Zealand’s wine is produced in the Marlborough region, and the vines generally require irrigation using groundwater. Our in-situ measurements of drainage and leaching show that there is net drainage-recharge of groundwater, and that the nitrate concentrations in the leachates are less than the drinking water standard. Groundwater is being protected though a net aquifer recharge of about 100 mm·a−1. Our work in the UAE focussed on groundwater protection under the production of the obligate halophyte Salicornia using irrigation with the reject brine from a desalination unit. A leaching-fraction is needed to despatch the residual salts out of the rootzone back to groundwater. Our heuristic modelling predicts a hyperbolic rise in aquifer salinity. From an initial salt concentration of 18.8 kg·m−3 the concentration of salt would be predicted to reach about 100 kg·m−3 in just 40 years. Solutions to extend the life of these groundwaters could involve the use of zero-liquid-discharge desalination, or the conjunctive use of alternative waters, either directly, or indirectly via managed aquifer recharge. There are opportunities and challenges at the nexus. Solutions will rely on engineering science and technology.

Understanding the dynamic interactions between root-water uptake patterns and aboveground physiological traits is crucial for predicting the adaptability and sustainability of vegetation under increasing climatic pressure, especially in water-limited regions. However, knowledge regarding the relationship between water-uptake patterns and leaf physiological characteristics in deep-rooted trees remains limited. To address this, we conducted a study in a rainfed apple orchard on the Loess Plateau during the growing seasons from 2023 to 2025. We used stable water-isotopes measured monthly to quantify tree-water sources and simultaneously monitored key leaf-physiological traits, including leaf water potential and gas exchange parameters. Our results showed that the depletion of soil water in the 0-5 m layer was the fundamental driver behind shifts in water-uptake patterns. As this 0-5 m soil water storage gradually diminished from 1218 to 997 mm, apple trees progressively lowered their leaf water potential from -1.9 to -2.6 MPa, while exponentially increasing the contribution of deep (5-20 m) soil-water to total uptake from <5% to over 50%. The deep soil-water accessed through this active lower water-potential strategy enabled the trees to exhibit typical anisohydric behavior, maintaining stomatal conductance and photosynthetic rates that did not significantly decrease when leaf water potential dropped from -1.9 to -2.6 MPa. However, sustaining gas exchange at lower water potentials entails a clear trade-off. This was manifested as a decrease in leaf-level water use efficiency from 5.8 to 2.0 mu mol mmol(-1). We reveal an environment-adaptive mechanism centered on active deep-water foraging and provides valuable insights for the management and sustainable development of deep-rooted vegetation in water-limited regions.

Orchard expansion and perennial water use increasingly influence dryland ecohydrology by altering soil-water storage and land–atmosphere fluxes. However, coordination between canopy water loss and soil-water source dynamics across dry–wet transitions remain poorly understood. Across two growing seasons, we combined sap flow, meteorology, soil moisture, dual-isotope Bayesian mixing, and fine-root profiles in young (5-year-old) and mature (10-year-old) Malus asiatica stands in Inner Mongolia, China. The mature stand had significantly higher daily stand water use (Q), apparent canopy conductance (gc), and decoupling coefficient (Ω) in all periods, with the largest differences during the wet period (Q: 3.03 vs 0.84 mm d−1; gc: 0.204 vs 0.057 mol m−2 s−1; Ω: 0.328 vs 0.173). Hydrometeorological and soil-water relationships diverged most during the dry period: young-stand Q and gc remained associated with root-zone soil water, whereas mature-stand Q was associated mainly with atmospheric drivers. In the mature stand, the largest posterior contribution came from 0–20 cm soil water during the wet period (64.2%) and from 20–60 cm soil water during the dry period (42.8%). The young stand retained 0–20 cm soil water as its largest source across periods (49.7–52.4%), while 60–80 cm soil water was never dominant. Fine-root biomass at 0–20 cm accounted for 67.5% and 60.6% of sampled totals in young and mature stands, respectively, but did not predict source contributions. Linking continuous canopy fluxes with soil-water source partitioning advances process-level understanding of rainfed-orchard ecohydrology across moisture periods and developmental stages.

With climate change, drought-driven deep soil desiccation is an escalating threat to forest ecosystems. However, the interactions between plant performance and deep soil drying remain poorly understood. We integrated 0–6 m soil water profiles, fine root distributions, and plant physiological traits across an age gradient of poplar (Populus tomentosa and Populus euramericana) plantations, linking the spatiotemporal dynamics of dried soil layers (DSL) with tree eco-physiological responses. We propose the percentage of DSLT to root zone (PTR) as a new index accounting for DSL severity. Our results revealed that DSL severity followed a desiccation-to-alleviation trajectory, partially recovering around 25 years. Once PTR exceeded 50%, trees exhibited threshold responses of reduced growth rate and specific leaf area, regulation became more isohydric, and stomatal traits shifted toward smaller but more numerous apertures. Coarser roots remained in moist layers for water transport, while finer roots in drier layers to maximize uptake, reflecting combined drought tolerance and avoidance strategies. Our findings reveal the nonlinear development of DSL and identify a physiological threshold beyond which poplars initiate coordinated responses. We provide new insights into plant-soil water feedback mechanisms under long-term drying conditions.

Understanding how orchard water use and root-water uptake vary with stand age under contrasting moisture conditions is essential for developing precision water management in cold-arid regions. Sap flow monitoring and xylem stable isotope analysis were integrated to compare the water-use strategies of 5- and 10-year-old Malus asiatica stands in Inner Mongolia, China. Sap-flux density, stand water use (Q), canopy stomatal conductance (gc), and the canopy decoupling coefficient (Ω) were analyzed, and the contributions of soil water from different depths (0–80 cm) were quantified using δ18O. The results showed clear stand age- and moisture-dependent differences in both canopy water use and water uptake. Across the entire experimental period, total Q in the 10-year-old stand was 2.27 times that of the 5-year-old stand, and both Q and gc differed significantly between the two stands, with the greatest difference occurring during the wet period. During dry periods, the 5-year-old stand showed an earlier sap-flow peak followed by a rapid decline and no obvious midday plateau. The 10-year-old stand maintained a later peak and a broader plateau, indicating stronger capacity to sustain transpiration around midday. During dry periods, the decoupling Ω remained low in both stands being 0.04 in the 5-year-old stand and 0.09 in the 10-year-old stand. But decoupling increased markedly during the wet period, 0.07 and 0.20, respectively, with a steeper Ω–vapor pressure deficit (VPD) slope in the 10-year-old stand. This indicates greater plasticity in canopy-atmosphere coupling. Correlation analyses further indicated stronger soil-water limitation in the 5-year-old stand, whereas water use in the 10-year-old stand remained more responsive to atmospheric drivers. The strongest divergence in water uptake occurred during the wet period, when the 10-year-old stand relied mainly on shallow soil water, whereas the 5-year-old stand maintained a greater contribution from deep soil water. During dry periods, the contribution of deep soil water increased slightly in both stands, but shallow soil water still remained an important source. Overall, the 5-year-old stand exhibited a relatively conservative strategy characterized by lower Q, lower gc, and stronger dependence on deep soil water, whereas the 10-year-old stand showed a more opportunistic strategy that combined higher Q and higher gc with stronger exploitation of shallow soil water when it was available. Because the orchard was rainfed and SMSI remained below 0.4 during most of the growing season, these age-specific differences provide a basis for irrigation scheduling: moderate supplemental irrigation is needed in young stands to relieve early-season soil-water limitation and reduce dependence on deep soil water, whereas irrigation in mature stands should focus on rapidly maintaining shallow root-zone water availability during periods of high transpiration demand.

Accurate assessment of tree transpiration is essential for plantation water management but is limited by the spatial heterogeneity of stem sap flow. We investigated Populus tomentosa using sapwood dyeing and thermal dissipation probes under full drip irrigation (DIFI) and rainfed (CK) treatments. Results showed that under DIFI, deep soil water maintained synchronized outer and inner sap flux density (SFD) with small seasonal variation in the ratio of outer-to-inner SFD (ℛₒᵢ), exhibiting an outer-xylem-prioritized, inner-engaged radial pattern. In contrast, CK experienced deep soil water deficit, leading to substantially lower inner SFD and irregularly fluctuating ℛₒᵢ, resulting in persistent inner-layer limitation and greater radial divergence. The outer SFD responded more strongly to vapor pressure deficit and radiation (R² = 0.64–0.67) than the inner SFD (R² = 0.39–0.50). For azimuthal variation, a mixed-effects model detected a significant but small overall azimuth effect (F₃, ₂₇ = 4.94, P < 0.01), with only the north–south contrast significant in pairwise comparisons; however, tree-to-tree variation was the dominant source of heterogeneity. Neglecting azimuthal variation resulted in a 21.6% mean deviation in whole-tree transpiration estimates, whereas using two and three orientations reduced the mean deviation to 12.8% and 7.0%, respectively. Sapwood dyeing revealed that hydraulic pathways shifted from distinct sectoral patterns at the base to widely distributed pathways with increasing height. We conclude that sap-flow measurement strategies should be adjusted to stand soil-water conditions. In water-limited stands, probes covering both the outer and inner xylem are crucial to capture dynamic radial heterogeneity, while combining measurements from two to three orientations across multiple trees is needed to minimize errors arising from azimuthal and individual variation. These insights provide a basis for optimizing transpiration models and water-saving management practices in plantation ecosystems.

Efficient apple orchard water management under climate variability requires understanding how fruit load and water supply regulate branch-scale water use to optimize irrigation, yield, and fruit quality. During the summer of 2014, sap flow (SF) and maximum daily shrinkage (MDS) were measured in one branch from six apple trees (Malus domestica Borkh. Cv. ‘Jazz™’) using the Compensation Heat Pulse method and diameter variation sensors in an orchard near Havelock North, New Zealand. One west-oriented branch per tree, with diameters of 1.5 to 2.3 cm, was monitored alongside midday stem (ψs) and leaf (ψl) water potentials, leaf gas exchanges, leaf area index (LAI), and fruit dry matter per branch at the end of the growing season. Half of the trees were subjected to irrigation withdrawal after day of year (DOY) 31 (non-irrigated treatment), resulting in a significantly lower midday stem water potential (ψs) by DOY 56 (−1.03 MPa). Pre-harvest, SF and MDS were tightly correlated (r2 = 0.69), but this correlation decreased post-harvest (r2 = 0.16) due to reduced fluctuations in both SF and branch variations (BV). SF was normalized per unit of leaf area, categorizing branches into high and low LAI: fruit dry matter ratio. SF values were approximately 2.2 times higher for FI pre-harvest and remained 2-fold higher post-harvest, associated with lower ψl and higher midday leaf transpiration for FI. MDS was identified as a better indicator of mild water deficit compared to SF, with both measurements responding effectively to midday vapor pressure deficit and reference evapotranspiration values. Overall, MDS proved to be a more sensitive indicator of mild water deficit than SF, while fruit load exerted a persistent influence on branch water use, highlighting the value of branch-scale measurements for improving irrigation management in apple orchards.

Plant-available water and adequate soil aeration are two fundamental requirements for successful plant growth. These prerequisites have generally been assessed independently in relation to plant growth, with limited focus on their complementary and competing behavior in a soil-water matrix. In this study we introduce a corequisite index adopted from a complex number representation by linking soil-water (the real component) and soil-air (the imaginary component) as the orthogonal counterparts in an Argand diagram. The new corequisite index constitutes a soil-water component defined based on field capacity and permanent wilting point, and a soil-air component defined based on critical soil-gas diffusivity. To calibrate model parameters, the soil-water characteristics were measured in vadose soil profiles (0- to 60-cm depth) from 48 replicate sites. Results revealed that the corequisite index, with its magnitude (0.5-1) and corequisite angle (0-30 degrees) in the given range, provided the best combined soil water and aeration status for the selected soil. The majority of the selected soils were affected by insufficient aeration (gas diffusivity < 0.01) when at field capacity (drained to -10 kPa), requiring the soils to drain further (-50 to -100 kPa) to satisfy the corequisites. The derived soil aeration parameters showed promising relationships with measurable soil physical properties. We further recommend adopting a 15% volumetric soil air content as a general threshold for minimum soil aeration in the absence of measured soil-gas diffusivity data.

Pesticides can potentially cause undesirable adverse side effects on nontarget organisms, humans, and the environment (soils, surface, and groundwater resources) because pesticides are toxic by design and are deliberately released into the environment. Pesticide risk is a combination of the (eco)toxicological properties of the pesticide and the potential exposure of humans, flora, and fauna to the pesticide. This article gives a general introduction to pesticide fate in the environment, summarizes risks associated with the production, use, and disposal of pesticides, and provides an overview on current strategies and tools to minimize these risks.

Modernization of irrigation systems is considered to improve irrigation efficiency, save water, and increase crop yields in water-scare semi-arid regions. This study conducted a long-term (10-years) simulations evaluating the potential effects of three different irrigation scenarios on soil water and salt balances, and crop water productivity of cotton-wheat cultivation in the Hakra Branch Canal command of Punjab, Pakistan. The physically based agro-hydrological model, Soil–Water-Atmosphere-Plant (SWAP) was applied to simulate the long-term (2007–2017) effects of three irrigation scenarios; (1) current surface irrigation (baseline reference) based on local farmers observations, (2) improved precision surface irrigation system (PSIS), and (3) a high-efficiency irrigation system (HEIS). The HEIS scenario without a leaching fraction (noted as HEIS_noLF), defined as using sprinkler irrigation to bring the soil back to the field capacity, resulted in about 48

New data highlight the economic value of using nitrogen-rich saline waters, either from groundwater or reject brines from desalination units, to irrigate the halophytic crop Salicornia bigelovii for food, fodder, and fuel in a hyper-arid environment. The greatest benefit was achieved using pressure-compensated drippers. Field measurements of drainage and leaching under the crop showed that all of the salt and nitrogen from the groundwater was returned back to the aquifer as leachate. A simple, heuristic model of groundwater quantity and quality was developed to infer the environmental impacts of irrigating crops with saline and high-nitrate groundwater in a hyper-arid environment. The rise in solute concentration in groundwater is hyperbolic. The parameters needed for this simple model are the fraction of the land that is irrigated, the initial depth of the saturated thickness, the saturated water content, and the annual rate of evapotranspiration. An indicator of the time-rise is the number of years to double the solute concentration. This is ӨAho /2 ETC, where ӨA is the aquifer’s saturated water content, ho is the original thickness of the saturated layer, and ETc is the annual rate of crop evapotranspiration. The general model is simple and straightforward to parameterise to predict the evapoconcentration of groundwater salinity.

Summary The need for more-efficient agricultural use of irrigation water arises out of the increased competition for water resources and the greater pressure on irrigation practices to be environmentally friendly. Here, we use a simple water-balance approach to model soil-water storage changes for the purpose of better estimating the irrigation requirements for a range of field crops growing in the Auckland region of New Zealand. In this humid, maritime climate irrigation requirements can very greatly in time and with crop type. Such information is needed by the local authorities, for planning purposes to determine appropriate water right allocations for local growers. The model we have developed considers the root zone to be one dimensional, comprising a uniform soil of known hydraulic properties, and having plants with roots extending vertically to a known depth. Model output consists of daily values of the soil moisture stored in the root zone. Crop water use was calculated via the Penman-Monteith model, using a generalized coefficient for each crop. A threshold moisture level, which depends on a combination of soil and crop factors, is used trigger the irrigation events. Water drainage below the root zone is calculated from easily determined soil hydraulic properties, and the amount of water stored in the profile. We use a statistical analysis based on 25 years of weather data to provide answers to the questions of “how much” and ‘how often”, at any level of given risk of exceedence. Irrigation requirements were considered for a wide range of crops that grow in the Auckland region. Variation in rainfall and drainage are described using a gamma probability density function (PDF), while the variation in irrigation requirement was found to be capable of description using a Gaussian PDF. This general model of irrigation requirements is easily parameterised, and can be run for any crop-soil combination using the historical weather data. It can be used to consider requirements for any level of prescribed risk. It could even be developed further to quantify specific water right allocations, and subsequently it could be turned into a Decision Support Tool for defining good irrigation practice, even in real time.

Context More than 830 million ha of soils are salt affected, representing around 9% of the world’s land surface. Groundwater high in salt already covers some 16% of the land area. Saline water can be used effectively for irrigation by salt leaching to despatch the accumulated salts, but this can pose a risk of salinisation of groundwater. It is important that the efficacy of salt leaching is confirmed, and the impacts of salt loading below the rootzone can be assessed. Aims We examine the efficiency and impact of salt leaching to remove salt from the rootzone. Methods Our soil, a Typic Torripsamment, is the dominant soil across the Arabian Peninsula. We carried out detailed laboratory experiments of salt leaching dynamics via salt breakthrough curves, analytical modelling, and through the field monitoring of impacts. Key results Analytical solutions well predicted the salt breakthrough curves from repacked soil columns in the laboratory and we were able to confirm that all of the soil’s water was actively involved in transport, and that salt behaved as an inert tracer. The breakthrough curves were well predicted using a small solute dispersivity, so piston displacement was found to be a good assumption. Salt was easily flushed from the columns. To back this up in the field, soil sampling was carried out down to 1 m across 36 profiles after the harvest of a halophytic crop irrigated with saline water. Salt storage was only 1.8 kg m−2, even though 80 kg m−2 had been applied. This is a positive result for managing irrigation. Conclusions Salt leaching can maintain equable salinity in the rootzone. However, this leaching carried salt back to groundwater at 2–3 times the concentration of the applied water. We confirmed that the amount of salt leaching back to groundwater can be significant. Implications This salt dilemma will require careful management to achieve crop yields and protect the environment.

Soil moisture (SM) is essential for sustaining services from Earth's critical zone, a thinliving skin spanning from the canopy to groundwater. In the Anthropocene epoch, intensive afforestation has remarkably contributed to global greening and certain service improvements, often at the cost of reduced SM. However, attributing the response of SM in deep soil to such human activities is a great challenge because of the scarcity of long - term observations. Here, we present a 37 y (1985 to 2021) analysis of SM dynamics at two scales across China's monsoon loess critical zone. Site - scale data indicate that land - use conversion from arable cropland to forest/grassland caused an 18% increase in SM deficit over 0 to 18 m depth (P < 0.01). Importantly, this SM deficit intensified over time, despite limited climate change influence. Across the Loess Plateau, SM storage in 0 to 10 m layer exhibited a significant decreasing trend from 1985 to 2021, with a turning point in 1999 when starting afforestation. Compared with SM storage before 1999, the relative contributions of climate change and afforestation to SM decline after 1999 were -8% and 108%, respectively. This emphasizes the pronounced impacts of intensifying land - use conversions as the principal catalyst of SM decline. Such a decline shifts 18% of total area into an at - risk status, mainly in the semiarid region, thereby threatening SM security. To mitigate this risk, future land management policies should acknowledge the crucial role of intensifying land - use conversions and their interplay with climate change. This is imperative to ensure SM security and sustain critical zone services.

Food security is a key target in the UN Sustainable Development Goals (SDGs) and is also one of the biggest challenges for China, the largest developing country in population in the world. Massive attention has been directed to the future impacts of hydrometeorological extremes on crop yield. However, knowledge gaps still stand concerning the effectiveness of irrigation, as the largest water consumption sector, on agricultural production under different climate scenarios. Here we showed the drought based on the modified Palmer Drought Severity Index and analyzed the drought-induced wheat yield losses in irrigated and non-irrigated agriculture across China according to three methods including the Multiple Linear Regression method, Deep Learning algorithm, and Erosion-Productivity Impact Calculator model. We found that the droughts become more intensive in the future, and drought-induced wheat yield loss under RCP8.5 scenario was expected to reach 32–49%. Intercomparison of drought-induced wheat yield changes between irrigated and non-irrigated agriculture indicated significantly less drought-induced crop-yield losses given sufficient irrigation under the RCP2.6 and RCP6.0 scenarios. However, our results under RCP8.5 suggested that the effectiveness of irrigation in enhancing food security is minor under this high-emission future climate scenario. These findings allowed us to revisit the effectiveness of irrigation in a warming climate and highlighted the importance of climate change mitigation in food security.

We sought to assess the impact on groundwater of using three types of saline waters to irrigate the halophyte Salicornia bigelovii Torrey in the hyper-arid United Arab Emirates. These were groundwater (GW) at 25 dS m-1, reverse-osmosis brine (RO) from a desalination unit at 40 dS m-1, and the aquabrine (AQ) effluent from land -based aquaculture in tanks filled with RO brine, also at 40 dS m-1. The three waters were applied through bubblers (BUB), pressure-compensated drippers (PCD), or subsurface irrigation tape (SUB). The yields of Sali-cornia fresh tips, harvest forage, and seed were greatest for AQ applied through BUB, being 650 g m- 2. We found 2-2.6 kg m- 2 for dry forage yield with AQ through BUB, compared with 1-2.3 kg m- 2 for the other waters and emitter devices. The highest water productivities WPI (kg m-3) across all three crop-outputs came from Aqua -brine applied by pressure-compensated drippers. We assessed the gross economic water productivity (GEWPI, $ m-3) based solely on gross revenue. The GEWPI was highest for AQ applied through PCD and SUB, namely 5.8-6.2 $ m- 3. The value derives primarily from fresh tips. The GEWPl was well above the cost of desalination at $1.5 m- 3. We measured drainage and leaching using fluxmeters. The greatest salt load to groundwater came from BUB, being 135-195 kg m- 2. For PCD and SUB it was between 14 and 36 kg m- 2. Mass-balance calculations of these salt loadings can predict the impact on the saline quality of aquifers. We used an exemplar loading of 75 kg m- 2, and results in an annual salinity rise of 2.6 dS m-1 y-1 for an aquifer of saturated depth of 100 m. This significant rate of rise in the salinity of groundwater would represent a continuing deterioration in the utility of groundwater.

Many tree species have developed extensive root systems that allow them to survive in arid environments by obtaining water from a large soil volume. These root systems can transport and redistribute soil water during drought by hydraulic redistribution (HR). A recent study revealed the phenomenon of evaporation-driven hydraulic redistribution (EDHR), which is driven by evaporative demand (transpiration). In this study, we confirmed the occurrence of EDHR in Chinese white poplar (Populus tomentosa) through root sap flow measurements. We utilized microcomputed tomography technology to reconstruct the xylem network of woody lateral roots and proposed conceptual models to verify EDHR from a physical perspective. Our results indicated that EDHR is driven by the internal water potential gradient within the plant xylem network, which requires 3 conditions: high evaporative demand, soil water potential gradient, and special xylem structure of the root junction. The simulations demonstrated that during periods of extreme drought, EDHR could replenish water to dry roots and improve root water potential up to 38.9% to 41.6%. This highlights the crucial eco-physiological importance of EDHR in drought tolerance. Our proposed models provide insights into the complex structure of root junctions and their impact on water movement, thus enhancing our understanding of the relationship between xylem structure and plant hydraulics.

The temporal variations of latent heat flux (AET) and its affecting factors vary from seconds to decades, and alter with crop species. Understanding the temporal coherence between AET and its influencing factors across different underlying surfaces is a crucial research topic with practical implications, and can enable better water man-agement. To investigate this, we conducted a study in southern China measuring water and heat fluxes over flooded rice-winter wheat rotation fields from 2017 to 2021. Wavelet transform technology was employed to analyze the spectral properties of AET and its affecting factors. Results showed that the power spectra of AET exhibited different cascade laws for rice and winter wheat. The spectral variabilities of AET occurred at daily and seasonal time scales for both rice and winter wheat, and an additional weekly time-scale for rice. Furthermore, the cospectrum between AET and soil water content (SWC) for rice showed a significant temporal correlation at 2-4 days, indicating the period of water input. We found that the daily AET of both crops changed synchronously with daily net radiation (Rn), and preceded daily vapor pressure deficit (VPD) and air temperature (Ta) by 1.5-2.6 h. The phase angle between AET and Ta was significantly lower for rice (mean = 1.8 h) than winter wheat (mean = 2.3 h). Partial wavelet coherence revealed that Rn, followed by VPD, was the main meteorological factor affecting AET for the rotated flooded rice-winter wheat system at each time scale, especially at the daily time scale. Additionally, the effect of VPD on AET was lower for winter wheat than rice at scales below a month. These findings offered a useful insight into selecting models of AET for varying time scales and promoting better agricultural water management.

Danube countries have witnessed numerous waves of drought events, causing significant agro-economic loss, but three consecutive dry years amplified the debate on how to deal with future drought risk. The European drought of 2022 has shown how important it is to look at food security from an environmental droughts risk assessment approach. The coupling drought–yield losses framework derives from the understanding that all land systems are connected through coupled human and natural systems, and these social, ecological, and agro-economic impacts are the result. Maize is considered a commodity and a staple food in Europe with the largest market share in global maize exports. Drought–heat stress, war and subsequent limitations on Ukrainian trade have created a shortage of maize supply in 2022 over Europe. This study focused on eighteen countries where maize production becomes highly susceptible to drought in the Danube River Basin (DRB; Austria, Bosnia and Herzegovina, Bulgaria, Croatia, the Czech Republic, Hungary, Montenegro, Romania, Serbia, Slovakia, and Slovenia). To understand the coupling drought–yield losses mechanism, time series of maize yield datasets and multiple remote sensing indices were used on arable lands for 278 districts at a high spatial resolution. The main objective of this study was to determine which regions respond to the changes in the rate of evapotranspiration and soil moisture and in which period and how much maize production is affected. The time series of the two-band enhanced vegetation index (EVI2), the evaporative stress index (ESI), and the relative water availability (AWR) were calculated. The spatial evolution of the ESI for 4-week and 12-week time windows, EVI2, and relative soil saturation at the topsoil and rootzone layers demonstrate the progress of agricultural drought under varying agroclimatic conditions and its impacts on maize yields. Our study adopted a novel mechanism-based risk assessment approach using a four-variate C-vine copula in the perspective of modelling yield losses. To assess how much maize production can be limited by drought stress, the weekly dynamics of the strength of bivariate linkage of eight compound modes were provided. The return periods of drought–yield losses signatures in the study region were less than 4 years. The highest chances (once every 2.50–2.86 years) of the occurrence of drought–yield losses signature occurred in Romania, Bulgaria, Slovakia, Bosnia and Herzegovina. The availability of soil water is one of the crucial indicators (AWR40) that explain the high degree of yield variability. This is an alarming finding given the expected or increasing year-to-year variability in soil moisture in these regions. The joint cumulative distribution function (FCROP, ESI, AWR40, AWR100) suggests that shorter-term ESI will be most beneficial for maize yield estimation in agricultural districts where crop productivity is primarily impaired by warmer and drier events. This combination of effects can cause short-term compound hot and dry extremes characterized by rapid onset, severe intensity, and devastating impacts on crop production. Droughts between 2015 and 2022 challenged governments across the Danube basin and highlighted the need for intergovernmental interactions and coordination. For the DRB area, user-oriented drought monitoring portals are already providing real-time information about drought occurrences and intensity to practitioners, but drought-yield loss assessments for such predictions for most of the region have been lacking.

There is a need to understand the link between the impacts on groundwater and the benefits when using saline waters to irrigate halophytes growing on Torripsamment desert soils in hyper-arid environments. We set up a pilot trial near Dubai using irrigation with highly saline waters with electrical conductivities (EC) between 25 and 40 dS m-1. Two difficulties were encountered. One related to our inability to measure the soil's water content. Our three-wire time domain reflectometer (TDR) probes could not measure the water content because of the high electrical conductivity. But by shielding all three wires of the TDR probe with glue-lined heat-shrink we found that Topp's TDR equation applied, and we could measure the rise in water content during the daily irrigations. Initially our passive-tension drainage fluxmeters (DFM) did not register drainage at a depth of 600 mm. We considered the failure of the DFMs was due to the disturbance of the calcic and gypsic materials at depth, such that when the re-packed soil was s re-wet it formed an impermeable layer. We installed the top of the DFMs at a depth of 200 mm. We increased the diameter of the convergence ring from 150 mm to 250 mm for wider drainage capture and increased the wick length of the passive tension from 600 mm to 700 mm. Our measurements showed the DFMs found that the EC of the leachate could reach over two times that of the applied irrigation water.