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Metrics of water scarcity and stress have evolved over the last three decades from simple threshold indicators to holistic measures characterising human environments and freshwater sustainability. Metrics commonly estimate renewable freshwater resources using mean annual river runoff, which masks hydrological variability, and quantify subjectively socio-economic conditions characterising adaptive capacity. There is a marked absence of research evaluating whether these metrics of water scarcity are meaningful. We argue that measurement of water scarcity (1) be redefined physically in terms of the freshwater storage required to address imbalances in intra- and inter-annual fluxes of freshwater supply and demand; (2) abandons subjective quantifications of human environments and (3) be used to inform participatory decision-making processes that explore a wide range of options for addressing freshwater storage requirements beyond dams that include use of renewable groundwater, soil water and trading in virtual water. Further, we outline a conceptual framework redefining water scarcity in terms of freshwater storage.

The increasing water use for human activities is threatening the health of ecosystems. Most previous studies on water scarcity mainly centered on human society. In this study, we developed a new indicator, ecological water scarcity (WS eco ), that considers water quantity, water quality, and environmental flow requirements. WS eco was assessed at the provincial level in China. The results show that northern China suffered more severe WS eco than southern China. In addition, the WS eco level decreased in 65% of provinces from 2016 to 2019, implying the great achievement of China’s effort in saving water and reducing pollution. The main driving factor of WS eco in most provinces was pollution rather than human water use. The findings of this study demonstrate the spatial distribution, temporal dynamics, and driving factors of WS eco in China. The results can be used to guide efforts for ecological restoration and sustainable water management in different regions.

Water security assessments often rely on outputs from hydrological models that are applicable only in gauged regions where there are river discharge data to constrain the models. Therefore, there is an urgent need to explore new methods for assessing water security in ungauged regions. This study proposes the use of the water balance and water footprint concepts and satellite observations to assess water security in Anglophone Cameroon, which is an example of a typically ungauged region. Specifically, the study assesses demand-driven water scarcity in terms of blue and green water scarcities and population-driven water scarcity quantified using the Falkenmark index across all districts in Anglophone Cameroon. The study also performs a spatiotemporal trend analysis of precipitation and temperature in the study area using the Mann–Kendall test. Precipitation trend analysis returns varying strengths and magnitudes for different districts unlike temperature which demonstrates an upward trend in all districts. The water security assessment shows that blue water scarcity is substantially low across most districts, whereas population-driven water scarcity is observed in densely populated districts (<1,700 m3/capita/year). The results from this study suggest that the proposed method may be used to assess water security in ungauged regions irrespective of climate or population size.

The present study aimed to determine the effects of biostimulants on the physicochemical parameters of the agricultural soil of quinoa under two water regimes and to understand the mode of action of the biostimulants on quinoa for drought adaptation. We investigated the impact of two doses of vermicompost (5 and 10 t/ha) and arbuscular mycorrhizal fungi applied individually, or in joint application, on attenuating the negative impacts of water shortage and improving the agro-physiological and biochemical traits of quinoa, as well as soil fertility, under two water regimes (well-watered and drought stress) in open field conditions. Exposure to drought decreased biomass, leaf water potential, and stomatal conductance, and increased malondialdehyde and hydrogen peroxide content. Mycorrhiza and/or vermicompost promoted plant growth by activating photosynthesis machinery and nutrient assimilation, leading to increased total soluble sugars, proteins, and antioxidant enzyme activities in the leaf and root. After the experiment, the soil’s total organic matter, phosphorus, nitrogen, calcium, and soil glomalin content improved by the single or combined application of mycorrhiza and vermicompost. This knowledge suggests that the combination of mycorrhiza and vermicompost regulates the physiological and biochemical processes employed by quinoa in coping with drought and improves the understanding of soil–plant interaction.

Precise measurement of water scarcity is a prerequisite to effective resource management. Researchers have developed a range of water scarcity indicators. However, no single indicator grasping all dimensions is available. In this paper, we compared 12 indicators for their sensitivity to blue and green waters, quality-induced water scarcity, environmental flows, data requirements, spatial scale, and adaptive capacity. Also, an analysis was carried out based on previous studies to identify hotspots and show the dissimilarity in the results yielded by different indicators. We found four classical indicators considered in this study deficient in accuracy given their insensitivity to green water, quality-induced water scarcity, environmental flow requirement, seasonality, virtual water, and so on. Whereas, seven holistic indicators face the challenges of data scarcity, validation, and lack of widespread application. None of these indicators is inclusive enough to provide a broad-gauge assessment. Finally, we provided a profound discussion on the limitations and needs of creativity in indicators and the data challenges. We concluded that water scarcity measurement in a country or region should not be based on a single indicator. A country-specific selection of multiple indicators should be made to cover the maximum parameters in view of spatial scale and data requirements.

The Sustainable Development Goal (SDG) 6, calling for access to safe water and sanitation for all by the year 2030 supports the efforts in water-scarce countries and regions to go beyond conventional resources and tap unconventional water supplies to narrow the water demand-supply gap. Among the unconventional water resources, the potential to collect water from the air, such as fog harvesting, is by far the most under-explored. Fog water collection is a passive, low maintenance, and sustainable option that can supply fresh drinking water to communities where fog events are common. Because of the relatively simple design of fog collection systems, their operation and maintenance are minimal and the associated cost likewise; although, in certain cases, some financially constrained communities would need initial subsidies. Despite technology development and demonstrated benefits, there are certain challenges to fog harvesting, including lack of supportive policies, limited functional local institutions, inexpert communities, gender inequality, and perceived high costs without undertaking comprehensive economic analyses. By addressing such challenges, there is an opportunity to provide potable water in areas where fog intensity and duration are sufficient, and where the competition for clean water is intensifying because water resources are at a far distance or provided by expensive sources.

The adoption of the water footprint concept and its application in assessing water stress can provide valuable insights into the sustainable use of water resources in agricultural production. The objective of the present study is to calculate the agricultural water stress index (AWSI) using the water footprint framework and water scarcity indices, namely blue water scarcity (BWS), water stress index (WSI), water self-sufficiency (WSS), water dependency (WD), and water poverty (WP) indices in Iran’s agricultural sector during the period of 2008–2019. Subsequently, the spatiotemporal patterns of water scarcity indices were examined at both the provincial and national levels. The findings reveal that the agricultural water footprint (AWF) amounted to approximately 195.6 Gm 3 , with AWF blue , AWF green , and AWF gray accounting for 85.2%, 6.9%, and 7.9%, respectively. The average national AWSI was estimated to be 0.94, indicating a state of extreme stress, and exhibiting an upward trend from 2012 to 2019. The southern and central regions, notably Yazd, Kerman, Tehran, and Hormozgan, have experienced severe and extreme water stress (AWSI > 1.38). Conversely, the humid and Mediterranean regions in the north, northwest, and west of Iran experience varying degrees of low to moderate water scarcity. Nevertheless, the western region (West Azerbaijan) and the northwest region (Zanjan and Hamedan) have transitioned from a state of moderate stress to a high-stress category (AWSI > 0.6). Based on the results, regions where BWS < AWSI < WSI exhibit lower levels of WP and WSS, but higher levels of WD. Conversely, in regions where AWSI > BWS > WSI, the significant diversity of agricultural products has contributed to an increase in WP and WSS, along with a decrease in WD. The AWSI, based on the water footprint concept, proves to be more suitable for reflecting regional water scarcity compared to existing water stress indices, particularly in arid and semi-arid agricultural production regions, due to the demonstrated environmental impacts of sustainable agricultural production.

Irrigation expansion is often posed as a promising option to enhance food security. Here, we assess the influence of expansion of irrigation, primarily in rural areas of the contiguous United States (CONUS), on the intensification and spatial proliferation of freshwater scarcity. Results show rain-fed to irrigation-fed (RFtoIF) transition will result in an additional 169.6 million hectares or 22% of the total CONUS land area facing moderate or severe water scarcity. Analysis of just the 53 large urban clusters with 146 million residents shows that the transition will result in 97 million urban population facing water scarcity for at least one month per year on average versus 82 million before the irrigation expansion. Notably, none of the six large urban regions facing an increase in scarcity with RFtoIF transition are located in arid regions in part because the magnitude of impact is dependent on multiple factors including local water demand, abstractions in the river upstream, and the buffering capacity of ancillary water sources to cities. For these reasons, areas with higher population and industrialization also generally experience a relatively smaller change in scarcity than regions with lower water demand. While the exact magnitude of impacts are subject to simulation uncertainties despite efforts to exercise due diligence, the study unambiguously underscores the need for strategies aimed at boosting crop productivity to incorporate the effects on water availability throughout the entire extent of the flow networks, instead of solely focusing on the local level. The results further highlight that if irrigation expansion is poorly managed, it may increase urban water scarcity, thus also possibly increasing the likelihood of water conflict between urban and rural areas.

Sustainable development requires modifying the current consumption pattern of natural resources. This study investigates efficient tactics for reducing the unsustainability and inefficiency of human’s food-related blue water consumption alongside improving national environmental and socioeconomic status. As a case study for Iran, 15 alternative management scenarios (AMS) were defined compared to the current on-farm management, and their effects were assessed on a monthly scale. Based on the results, 45.5 billion m³ y⁻¹ (BCM) blue water is consumed within the croplands, 78% and 34% of which are unsustainable and inefficient, respectively. AMCs reduces the unsustainable and inefficient blue water consumption by 2–17 BCM and 2–13 BCM, respectively. The combination of yield gap closure, drip irrigation, soil mulching, and deficit irrigation has the largest effect on blue water saving; it releases or changes the status of monthly blue water scarcity in 11 provinces; increases field-employees by 132%, food security by 9%, international food-export by 87%, and gross domestic production by 54%. However, it doesn’t fully address blue water overconsumption in the summer period; hence, further measures are needed to reduce blue water scarcity to the sustainable level in these environmental hotspots.

A dependable assessment of quality-induced water scarcity (QualWS) is essential for tackling the issue and achieving sustainable development goals. The conventional Emission-based grey water footprint (GWF) may over- or under-estimate QualWS, as it solely focuses on local pollutant emissions while disregarding other influential factors, such as water body self-purification capacity, transboundary water flows and the potential under- or over-estimation of water pollution emissions. To address this limitation, we propose the State-based GWF to reflect the quality status of local water resources accurately. The indicator is applied in annual and monthly QualWS assessments at the provincial scale in China. In 2021, 19 provinces were identified as QualWS hotspots, comprising seven moderate and 12 slight hotspots for at least one pollutant. Notably, the State-based assessment revealed eight previously overlooked hotspots undetected by conventional methods. Furthermore, total phosphorus emerged as the most critical water pollutant, followed by total nitrogen and chemical oxygen demand. Our assessment presents an innovative perspective for understanding QualWS and establishes a scientific basis for effective aquatic environment management.