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Feeding a growing population with global natural-resource constraints becomes an increasingly challenging task. Changing spatial cropping patterns could contribute to sustaining crop production and mitigating water scarcity. Previous studies on water saving through international food trade focussed either on comparing water productivities among food-trading countries or on analysing food trade in relation to national water endowments. Here, we consider, for the first time, how both differences in national average water productivities and water endowments can be considered to analyse comparative advantages of countries for different types of crop production. A linear-optimization algorithm is used to find modifications in global cropping patterns that reduce national blue water scarcity in the world's most severely water-scarce countries, while keeping global production of each crop unchanged and preventing any increase in total irrigated or rainfed harvested areas in each country. The results are used to assess national comparative advantages and disadvantages for different crops. Even when allowing a maximum expansion of the irrigated or rainfed harvested area per crop per country of only 10 %, the blue water scarcity in the world's most water-scarce countries can be greatly reduced. In this case, we could achieve a reduction of the global blue water footprint of crop production of 21 % and a decrease of the global total harvested and irrigated areas of 2 % and 10 % respectively. Shifts in rainfed areas have a dominant share in reducing the blue water footprint of crop production. How to cite. Chouchane, H., Krol, M. S., and Hoekstra, A. Y.: Changing global cropping patterns to minimize national blue water scarcity, Hydrol. Earth Syst. Sci., 24, 3015–3031, https://doi.org/10.5194/hess-24-3015-2020, 2020.

Human consumption of freshwater is now approaching or surpassing the rate at which water sources are being naturally replenished in many regions, creating water shortage risks for people and ecosystems. Here we assess the impact of human water uses and their connection to water scarcity and ecological damage across the United States, identify primary causes of river dewatering and explore ways to ameliorate them. We find irrigation of cattle-feed crops to be the greatest consumer of river water in the western United States, implicating beef and dairy consumption as the leading driver of water shortages and fish imperilment in the region. We assess opportunities for alleviating water scarcity by reducing cattle-feed production, finding that temporary, rotational fallowing of irrigated feed crops can markedly reduce water shortage risks and improve ecological sustainability. Long-term water security and river ecosystem health will ultimately require Americans to consume less beef that depends on irrigated feed crops. Water use in river basins is an age-old resource-management question, but it is rare to quantify consumption by specific sectors. The Colorado River is being overused for beef and dairy production, endangering the entire river ecosystem.

Water pollution by veterinary antibiotics (VAs) resulting from livestock production is associated with severe environmental and human health risks. While upward trends in global animal product consumption signal that these risks might exacerbate toward the future, VA related water pollution is currently insufficiently understood. To increase this understanding, the present research assesses processes influencing VA pollution from VA administration to their discharge into freshwater bodies, using an integrated modelling approach (IMA). For the VAs amoxicillin, doxycycline, oxytetracycline, sulfamethazine, and tetracycline we estimate loads administered to livestock, excretion, degradation during manure storage, fate in soil and transport to surface water. Fate and transport are modelled using the VA transport model (VANTOM), which is fed with estimates from the Pan-European Soil Erosion Risk Assessment (PESERA). The grey water footprint (GWF) is used to indicate the severity of water pollution in volumetric terms by combining VA loads and predicted no effect concentrations. We apply our approach to the German-Dutch Vecht river catchment, which is characterized by high livestock densities. Results show a VA mass load decrease larger than 99% for all substances under investigation, from their administration to surface water emission. Due to metabolization in the body, degradation during manure storage and degradation in soil, VA loads are reduced by 45%, 80% and 90% on average, respectively. While amoxicillin and sulfamethazine dissipate quickly after field application, significant fractions of doxycycline, oxytetracycline and tetracycline accumulate in the soil. The overall Vecht catchment's GWF is estimated at 250,000 m3 yr−1, resulting from doxycycline (81% and 19% contribution from the German and Dutch catchment part respectively). Uncertainty ranges of several orders of magnitude, as well as several remaining limitations to the presented IMA, underscore the importance to further develop and refine the approach.

Bioethanol productionfrom non-crop basedlignocellulosicmaterial has reached the commercial scale and is advocated as a possible solution to decarbonize the transport sector. This study evaluates how much presently used transport related fossil fuels can be replaced with lignocellulosicbioethanolusing crop residues, calculates greenhouse gas emission savings, and determines lignocellulosic bioethanol's land, water, and carbon footprints. We estimate global bioethanol production potential from 123 crop residues in 192 countries and 20 territories under different environmental constraints (optimistic and realistic sustainable potentials) versus no constraints (theoretical potential) on residue availability. Previous studies on global bioethanol production potential fromlignocellulosic materialfocused on one or few biomass feedstocks, and excluded (un)constrained residue availability scenarios. Our results suggest the global net lignocellulosic bioethanol output ranges from 7.1 to 34.0EJ per annum replacing between 7% and 31% of oil products for transport yielding relative emission savings of 338 megatonne (Mt; 70%) to 1836Mt (79%). Emission savings range from 4% to 23% of total transport emissions in the realistic sustainable versus theoretical potential. Land, water and carbon footprints of net bioethanol vary between potentials, countries/territories, and feedstocks, but overall exceed footprints of conventional bioethanol. Averaged footprints range between 0.14 and 0.24m2land per megajoule (MJ−1), 74–120L water MJ−1, and 28–44g CO2equivalent MJ−1, with smaller footprints in the theoretical potential caused by the exclusion of secondary residues and low price of alternative biomass chains in the sustainable potential.

It has become common practice to speak about ‘green’ versus ‘blue’ water consumption, in order to distinguish between consumption of rainwater versus groundwater or surface water. The two sources of water differ in terms of possibilities for storage and use. Whereas industrial, municipal and livestock water supply primarily depend on blue water, crop cultivation relies on both green and blue water. Discriminating between green and blue water consumption in a crop field is not straightforward: consumption refers to evapotranspiration (ET) and water contained in the harvested crop, which both appear in undifferentiated form. One cannot see which part of ET or the water in a plant originates from rainwater and which part from irrigation water. In this paper I propose a generic and physically based method to differentiate green and blue evaporation (E) and green and blue transpiration (T) by daily accounting of the fractions green and blue water in each soil and vegetation layer. The green and blue fractions of all water fluxes leaving a soil or vegetation layer in a day depend on the average green and blue water fractions in that soil or vegetation layer during that day. This method allows for an accurate assessment of irrigation efficiency (the ratio of blue water transpiration to the irrigation water applied), and for a precise estimation of green and blue water footprints of crop production (the ratio of either green ET or blue ET to the crop yield).

Significance Precipitation over land partitions into runoff via surface water and groundwater (blue water) and evapotranspiration (green water). We expand the traditional debate on water scarcity, which solely focuses on blue water, by assessing green water scarcity. The current debate on water scarcity is heavily skewed, since it leaves unnoticed the bulk of water availability––which is green––and the bulk of water use––which is also green. Green water is the main source of water to produce food, feed, fiber, timber, and bioenergy. Thus, to understand how freshwater scarcity constrains the production of these vital goods, explicating and including (limits to) green water use is imperative., Green water––rainfall over land that eventually flows back to the atmosphere as evapotranspiration––is the main source of water to produce food, feed, fiber, timber, and bioenergy. To understand how freshwater scarcity constrains production of these goods, we need to consider limits to the green water footprint (WFg), the green water flow allocated to human society. However, research traditionally focuses on scarcity of blue water––groundwater and surface water. Here we expand the debate on water scarcity by considering green water scarcity (WSg). At 5 × 5 arc-minute spatial resolution, we quantify WFg and the maximum sustainable level to this footprint (WFg,m), while accounting for green water requirements to support biodiversity. We then estimate WSg per country as the ratio of the national aggregate WFg to the national aggregate WFg,m. We find that globally WFg amounts to 56% of WFg,m, and overshoots it in several places, for example in countries in Europe, Central America, the Middle East, and South Asia. The sustainably available green water flows in these countries are mostly or fully allocated to human activities (predominately agriculture and forestry), occasionally at the cost of green water flows earmarked for nature. By ignoring limits to the growing human WFg, we risk further loss of ecosystem values that depend on the remaining untouched green water flows. We emphasize that green water is a critical and limited resource that should explicitly be part of any assessment of water scarcity, food security, or bioenergy potential.

Water scarcity has received global attention in the last decade as it challenges food security in arid and semi-arid regions, particularly in the Middle East and North Africa. This research assesses the possible alleviation of water scarcity by reducing the water footprint in crop production through the application of soil mulching and drip irrigation. The study is the first to do so at catchment scale, taking into account various crops, multi-cropping, cropping patterns, and spatial differences in climate, soil, and field management factors, using field survey and local data. The AquaCrop-OS model and the global water footprint assessment (WFA) standard were used to assess the green and blue water footprint (WF) of ten major crops in the Upper Litani Basin (ULB) in Lebanon. The blue water saving and blue water scarcity reduction under these two alternative practices were compared to the current situation. The results show that the WF of crop production is more sensitive to climate than soil type. The annual blue WF of summer crops was largest when water availability was lowest. Mulching reduced the blue WF by 3.6% and mulching combined with drip irrigation reduced it by 4.7%. The blue water saving from mulching was estimated about 6.3 million m3/y and from mulching combined with drip irrigation about 8.3 million m3/y. This is substantial but by far not sufficient to reduce the overall blue WF in summer to a sustainable level at catchment scale.

Pakistan possesses the fourth largest irrigation network in the world, serving 20.2 million hectares of cultivated land. With an increasing irrigated area, Pakistan is short of freshwater resources and faces severe water scarcity and food security challenges. This is the first comprehensive study on the water footprint (WF) of crop production in Peshawar Basin. WF is defined as the volume of freshwater required to produce goods and services. In this study, we assessed the blue and green water footprints (WFs) and annual blue and green water consumption of major crops (maize, rice, tobacco, wheat, barley, sugarcane, and sugar beet) in Peshawar Basin, Pakistan. The Global Water Footprint Assessment Standard (GWFAS) and AquaCrop model were used to model the daily WF of each crop from 1986 to 2015. In addition, the blue water scarcity, in the context of available surface water, and economic water productivity (EWP) of these crops were assessed. The 30 year average blue and green WFs of major crops revealed that maize had the highest blue and green WFs (7077 and 2744 m3/ton, respectively) and sugarcane had the lowest blue and green WFs (174 and 45 m3/ton, respectively). The average annual consumption of blue water by major crops in the basin was 1.9 billion m3, where 67% was used for sugarcane and maize, covering 48% of the cropland. The average annual consumption of green water was 1.0 billion m3, where 68% was used for wheat and sugarcane, covering 67% of the cropland. The WFs of all crops exceeded the global average. The results showed that annually the basin is supplied with 30 billion m3 of freshwater. Annually, 3 billion m3 of freshwater leaves the basin unutilized. The average annual blue water consumption by major crops is 31% of the total available surface water (6 billion m3) in the basin. Tobacco and sugar beet had the highest blue and green EWP while wheat and maize had the lowest. The findings of this study can help the water management authorities in formulating a comprehensive policy for efficient utilization of available water resources in Peshawar Basin.

China’s rapid growth was fueled by investments that grew more than 10-fold since 1995. Little is known about how the capital assets acquired, while being used in productive processes for years or decades, satisfy global final consumption of goods and services, or how the resource use and emissions that occurred during capital formation are attributable to past or future consumption. Here, enabled by a new global model of capital formation and use, we quantify the linkages over the past 2 decades and into the future between six environmental pressures (EPs) associated with China’s capital formation and attributable to Chinese as well as non-Chinese consumption. We show that only 35% of the capital assets acquired by China from 1995 to 2015, representing 32–39% of the associated EPs (e.g., water consumption, greenhouse gas (GHG) emissions, and metal ore extractions), have been depreciated, while the majority rest will serve future production and consumption. The outsourcing of capital services and the associated EPs are considerable, ranging from 14 to 25% of depending on the EP indicators. Without accounting for the capital–final consumption linkages across time and space, one would miscalculate China’s environmental footprints related to the six EPs by big margins, from −61% to +114%.

The concept of a sustainable green city based on Sustainable Development Goals (SDGs)–Goal 11 - sustainable cities and communities – may not be narrowed down to solely intensifying urban green spaces. Sustainability could include urban water management to alleviate possible conflict among “water‐saving” and “greening cities” strategies. Water consumption by urban greenery has a major role in urban water management, particularly in water-scarce regions where green covers are most affected by drought and aridity. More green and blue water resources are required to maintain and expand urban green spaces. Quantifying the water footprint of urban greenery helps to balance greening cities while water saving from both green and blue water resources. We employed remote sensing and artificial intelligence techniques to assess the water consumption and water footprint of a 780‐ha public green space, the Adelaide Parklands in Australia. We estimated the green and blue water footprint of this green space (containing 29 parks) during 2010-2018 on a monthly basis. Our results showed that the mean total water footprint of the Adelaide Parklands was about 7.75 gigaliter per annum over 2010-2018; it varied from 7.19 gigaliter/year in 2018 to 8.45 gigaliter/year in 2012. The blue water footprint was consistently higher than the green water footprint even in wet time of the year. We suggest implementing sponge city and water sensitive urban design (WSUD) techniques to help greening cities while reducing the water footprint of urban green spaces. These approaches have the potential to lessen the pressure on blue water resources and optimise the consumption of green water resources.

Integrating the social and natural sciences to effectively tackle the intertwined challenges represented by the Sustainable Development Goals (SDGs) has been advocated for years. However, the practice is challenging, especially with respect to the beliefs, morals, and practices of individuals and groups or, more succinctly put, culture, which, despite attracting growing awareness, remains understated in sustainability. Here, we examine how and to what extent cultural values are linked to the achievement of the SDGs. Synthesizing knowledge from more than 300 publications, we show that cultural traits are linked to the achievement of all 17 SDGs and 79% of SDG targets. Further, empirical understanding obtained from a panel data analysis highlights that cultural values explain as much as 26% of the variations in the SDG achievements, yet the links are strikingly divergent across cultural traits and indicators. Our findings imply the need to consider more cultural contexts and nuances in sustainability science communications and policy design and to develop new cross-disciplinary solutions to sustainability challenges. For a long time, sustainability science and policy design have been rooted in environmental and economic perspectives, leaving the role of culture undervalued. Although a growing number of scholars and organizations, such as the United Nations Educational, Scientific and Cultural Organization (UNESCO), have realized the importance of culture in sustainable development and made substantial effort to integrate them, the debates against conventional sustainability discourses remain challenging. Our analysis contributes to the debate by providing both a conceptual framework and empirical evidence on the relations between cultural values and the achievement of the Sustainable Development Goals (SDGs). Our findings imply the necessity to consider more cultural context and nuances in sustainability science communication and policy design. In particular, sustainable development is suggested to be tailored to, but not be captive of, cultural context. The role of culture in sustainable development has received increasing attention but remains undervalued. We bridge culture and the Sustainable Development Goals (SDGs) in both qualitative and quantitative manners and convert the vague understanding of culture-SDG links to concrete evidence. We show that culture is linked to the attainment of all 17 SDGs, represented by 79% of the SDG targets. Culture additionally explains as much as 26% of the variations in the achievement of SDGs.

The FAO Livestock Environmental Assessment and Performance (LEAP) Partnership organised a Technical Advisory Group (TAG) to develop reference guidelines on water footprinting for livestock production systems and supply chains. The mandate of the TAG was to i) provide recommendations to monitor the environmental performance of feed and livestock supply chains over time so that progress towards improvement targets can be measured, ii) be applicable for feed and water demand of small ruminants, poultry, large ruminants and pig supply chains, iii) build on, and go beyond, the existing FAO LEAP guidelines and iv) pursue alignment with relevant international standards, specifically ISO 14040 (2006)/ISO 14044 (2006), and ISO 14046 (2014). The recommended guidelines on livestock water use address both impact assessment (water scarcity footprint as defined by ISO 14046, 2014) and water productivity (water use efficiency). While most aspects of livestock water use assessment have been proposed or discussed independently elsewhere, the TAG reviewed and connected these concepts and information in relation with each other and made recommendations towards comprehensive assessment of water use in livestock production systems and supply chains. The approaches to assess the quantity of water used for livestock systems are addressed and the specific assessment methods for water productivity and water scarcity are recommended. Water productivity assessment is further advanced by its quantification and reporting with fractions of green and blue water consumed. This allows the assessment of the environmental performance related to water use of a livestock-related system by assessing potential environmental impacts of anthropogenic water consumption (only “blue water”); as well as the assessment of overall water productivity of the system (including “green” and “blue water” consumption). A consistent combination of water productivity and water scarcity footprint metrics provides a complete picture both in terms of potential productivity improvements of the water consumption as well as minimizing potential environmental impacts related to water scarcity. This process resulted for the first time in an international consensus on water use assessment, including both the life-cycle assessment community with the water scarcity footprint and the water management community with water productivity metrics. EEA Rafaela Fil: Boulay, Anne-Marie. Sherbrooke University. LIRIDE; Canadá. Fil: Boulay, Anne-Marie. Polytechnique Montreal. CIRAIG; Canadá Fil: Drastig, Katrin. Leibniz Institute for Agricultural Engineering and Bioeconomy; Alemania Fil: Amanullah. University of Agriculture Peshawar. Faculty of Crop Production Sciences. Department of Agronomy; Paquistán Fil: Chapagain, Ashok. Pacific Institute; Estados Unidos Fil: Charlon, Veronica. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina Fil: Civit, Bárbara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ambiente, Hábitat y Energía; Argentina Fil: DeCamillis, Camillo. Food and Agriculture Organization of the United Nations (FAO); Italia Fil: Souza, Marlos De. Food and Agriculture Organization of the United Nations (FAO); Italia Fil: Hess, Tim. Cranfield University. Cranfield Water Science Institute; Reino Unido Fil: Hoekstra, Arjen Y. University of Twente. Twente Water Centre; Holanda Fil: Hoekstra, Arjen Y. National University of Singapore. Lee Kuan Yew School of Public Policy. Institute of Water Policy; Singapur Fil: Ibidhi, Ridha. National Institute of Agronomic Research of Tunisia. Department of Animal and Forage Production; Túnez Fil: Lathuillière, Michael J. Stockholm Environment Institute; Suecia Fil: Lathuillière, Michael J. University of British Columbia. Institute for Resources, Environment and Sustainability; Canadá Fil: Manzardo, Alessandro. University of Padova. Department of Industrial Engineering. CESQA; Italia Fil: McAllister, Tim. Lethbridge Research and Development Centre. Agriculture and Agri-Food Canada; Canadá Fil: Morales, Ricardo A. AgroDer SC; México Fil: Motoshita, Masaharu. National Institute of Advanced Industrial Science and Technology. Institute of Science for Safety and Sustainability; Japón Fil: Palhares, Julio Cesar Pascale. Embrapa Southeast Livestock; Brasil Fil: Pirlo, Giacomo. Research Centre for Animal Production and Aquaculture. Council for Agricultural Research and Economics; Italia Fil: Ridoutt, Brad. University of the Free State. Department Agricultural Economics; Sudáfrica Fil: Ridoutt, Brad. Commonwealth Scientific and Industrial Research Organisation (CSIRO). Agriculture and Food; Australia Fil: Russo, Valentina. University of Cape Town. Department of Chemical Engineering. Environmental and Process Systems Engineering Research Group; Sudáfrica Fil: Salmoral, Gloria. Cranfield University. Cranfield Water Science Institute; Reino Unido Fil: Salmoral, Gloria. University of Exeter. Environment and Sustainability Institute; Reino Unido Fil: Salmoral, Gloria. University of Exeter. College of Engineering, Mathematics and Physical Sciences; Reino Unido Fil: Singh, Ranvir. Massey University. School of Agriculture and Environment; Nueva Zelanda Fil: Vanham, Davy. Joint Research Centre. European Commission; Italia Fil: Wiedemann, Stephen. Integrity Ag and Environment; Australia Fil: Weichao, Zheng. China Agricultural University; China Fil: Pfister, Stephan. ETH-Zürich. Department of Civil, Environmental and Geomatic Engineering; Suiza

Population growth and rising affluence increase the demand for agricultural commodities. Associated growth in production increases dependency on natural resources in countries that attempt to meet part or all the new demand locally. This study assesses the impact of changing meat and milk production on natural resource use in Kenya under three plausible scenarios of socio-economic development, namely Business-As-Usual (BAU), Sustainable Development (SDP) and Kenya Vision 2030 (V2030) scenarios. The IMPACT model is used to develop projected livestock production parameters for meat and milk. The BAU and SDP represent standard scenarios for Kenya of a global economic model, IMPACT, while V2030 incorporates in the model features specific to Kenya’s medium-term national development plan. We use calculations of water footprint and land footprint as resource use indicators to quantify the anticipated appropriation of water and land resources for meat and milk production and trade by 2040. Though camel dairy production numbers increase the most by quadrupling between 2005 and 2040, it is cattle dairy production that significantly determined gains in production between the scenarios. Productivity gains under the SDP scenario does not match the investments made thereby leading to only slightly better values for water and land productivity than those achieved under the BAU scenario. Improvement in land productivity is the most dramatic for shoat milk production in the arid and semi-arid systems under the V2030 relative to the BAU scenario and is the least marked for milk production by cattle in the humid system under the V2030 relative to the BAU scenario. By quantifying water and land productivity across heterogenous production systems, our findings are aimed at aiding decision-makers in Kenya and other developing countries to understand the implication of strategies aimed at increasing domestic agricultural and livestock production on water and land resource both locally and through trade with other countries.

Increasing pressure on the world’s freshwater resources raises serious concerns about global food security and the sustainability of water use in agriculture. Here we quantify and map at a 5-arcmin spatial resolution the blue water footprint of each country’s national consumption and where they infringe sustainable environmental flows as defined by the presumptive environmental flow standard or the 80% rule, in which runoff depletion by more than 20% will pose risk to ecosystems. We find that 52% of the blue water footprint of global consumption and 43% of international blue virtual water flows come from places where the sustainable environmental flow is violated. About 22% of the environmental flow infringement of the blue water footprint of global consumption lies outside the specific countries of consumption, indicating that a number of them have externalized their impacts. By establishing a link between the consumption of a product in one place and water scarcity in places far from the place of consumption, our assessment may aid a dialogue on how to assign and share responsibilities concerning water use. Increasing pressure on the world’s water resources raises serious concerns about future food security. This global, spatially explicit assessment of water consumption reveals where and by how much sustainable blue water flows are infringed. The study covers 146 food items for 174 countries over 1996–2005.

Phosphorus (P) losses from fertilized croplands to inland water bodies cause serious environmental problems. During wet years, high precipitation disproportionately contributes to P losses. We combine simulations of a gridded crop model and outputs from a number of hydrological and climate models to assess global impacts of changes in precipitation regimes on P losses during the 21st century. Under the baseline climate during 1991-2010, median P losses are 2.7 ± 0.5 kg P ha-1 year-1 over global croplands of four major crops, while during wet years, P losses are 3.6 ± 0.7 kg P ha-1 year-1. By the end of this century, P losses in wet years would reach 4.2 ± 1.0 (RCP2.6) and 4.7 ± 1.3 (RCP8.5) kg P ha-1 year-1 due to increases in high annual precipitation alone. The increases in P losses are the highest (up to 200%) in the arid regions of Middle East, Central Asia, and northern Africa. Consequently, in three quarters of the world's river basins, representing about 40% of total global runoff and home up to 7 billion people, P dilution capacity of freshwater could be exceeded due to P losses from croplands by the end of this century.

Many cities are confronted with both water scarcity and urban flooding as centralized water infrastructures becoming increasingly inadequate in a changing climate. Decentralized infrastructures like rainwater harvesting (RWH) can ease both issues. Yet, most studies find RWH offers limited infrastructure capacity at high cost. Previous assessments, however, fail to consider two critical advantages: multi-functionality and high adaptability. By improving the incorporation of these advantages in our analysis of 1.06 million buildings with distinct design and water demand characteristics and 20-year hourly precipitation records in New York City (NYC), we demonstrate, contrary to existing studies, that strategically designed, financed and implemented rooftop RWH systems in all or a subset of the buildings can meet large-scale infrastructure development needs for water supply and stormwater management. RWH implementation featuring public-private partnerships (PPP) in 43-96% of the buildings can serve 17-29% of the city's non-drinking water demands while reducing the public expenditure per unit of water supply by 13-85%. The distributed citywide RWH implementations prevent 35-56% of rooftop runoff from entering the sewage system, rivers, and/or waterways per month, with observed rooftop runoff reductions as high as 90% for a single rain event.

Availability of sufficient and clean freshwater has become a growing constraint to sustainable agricultural development in many countries. We explore two pathways that hold the potential to reduce water consumption and pollution related to cereal production in Iran: reducing food waste and changing cropping patterns. Hereto, we first evaluated the green, blue and grey water footprint (WF) associated with production of wheat, barley and rice. Next, we assessed resulting water scarcity and pollution levels at the provincial scale, for the period 1980–2010. Both total WF and its blue water share were found to have increased considerably from 1980 on. For the year 2010 (a representative hydrological year), results show that the national total green–blue WF of production of these major cereals is 43 × 109 m3. Regarding the grey WF of production, 30 × 109 m3 was required to take up surplus N loads to water bodies. Resulting blue water scarcity and water pollution levels are highest in the arid and semi-arid provinces, caused in part by cereal production destined for export to other regions. Exploring reduction pathways showed that bridling cereal waste allows a potential reduction in both the green–blue WF and grey WF of production of up to 5% each. Relocating production areas and modifying cereal trade patterns from water-abundant to scarcer provinces could save up to 3.5% in the green–blue WF of production and up to 25% in the grey WF.

Water productivity benchmarks for irrigated and rainfed agriculture will provide relevant information to manage scarce water resources and control groundwater level decline. We analyse the temporal and spatial variation of the water productivity (WP) of maize and soybean in Nebraska, with WP defined as harvested crop weight per total evapotraspiration. The results show that WP of both maize and soybean increase from west to east within Nebraska and have increased over the last 25 years, mainly due to the increase in crop yields (land productivity). We derive WP benchmarks for each crop per climate zone. Increasing actual WPs in the state to benchmark levels will increase yields by 21 % for maize and by 19 % for soybean. The WP benchmark levels for the two crops presented here will help formulating targets for closing water productivity gaps and improving the sustainability of water use in the state.

Undernutrition, obesity, climate change, and freshwater depletion share food and agricultural systems as an underlying driver. Efforts to more closely align dietary patterns with sustainability and health goals could be better informed with data covering the spectrum of countries characterized by over- and undernutrition. Here, we model the greenhouse gas (GHG) and water footprints of nine increasingly plant-forward diets, aligned with criteria for a healthy diet, specific to 140 countries. Results varied widely by country due to differences in: nutritional adjustments, baseline consumption patterns from which modeled diets were derived, import patterns, and the GHG- and water-intensities of foods by country of origin. Relative to exclusively plant-based (vegan) diets, diets comprised of plant foods with modest amounts of low-food chain animals (i.e., forage fish, bivalve mollusks, insects) had comparably small GHG and water footprints. In 95 percent of countries, diets that only included animal products for one meal per day were less GHG-intensive than lacto-ovo vegetarian diets (in which terrestrial and aquatic meats were eliminated entirely) in part due to the GHG-intensity of dairy foods. The relatively optimal choices among modeled diets otherwise varied across countries, in part due to contributions from deforestation (e.g., for feed production and grazing lands) and highly freshwater-intensive forms of aquaculture. Globally, modest plant-forward shifts (e.g., to low red meat diets) were offset by modeled increases in protein and caloric intake among undernourished populations, resulting in net increases in GHG and water footprints. These and other findings highlight the importance of trade, culture, and nutrition in diet footprint analyses. The country-specific results presented here could provide nutritionally-viable pathways for high-meat consuming countries as well as transitioning countries that might otherwise adopt the Western dietary pattern.

The world’s population residing in urban areas grew from 30% in 1950 to about 60% in 2020 and is expected to reach 68% by 2050. As urban areas continue to grow, green spaces in cities are getting ever more treasured. Most cities have adopted strategies to be greener to improve their resilience and livability. To make the best of the benefits offered by urban green spaces, healthy greenness is essential and this means additional water consumption. Water limitation usually results in drying out of green areas in summer, when benefits and services by green spaces are highly demanded (e.g. cooling effect). In the 21st century, vulnerability to water shortage is not restricted to dry regions anymore; water scarcity in the time of need is threatening the livability of cities even in wet regions (i.e. extreme summers in Europe). In this study, we estimate for the first time, to our knowledge, the blue water consumption of urban green spaces. We measure the evapotranspiration of an urban green space using three approaches of in-situ, observational-based and remote sensing, and employ principles of water footprint. We assess the blue and green water footprint of urban greenery to maintain green areas of a city based on their water demand, not the abstracted water or irrigated water. In the case of Adelaide Parklands in Australia, the annual total water footprint is 1114mm, of which 17% consumes in spring, 42% in summer, 27% in autumn, and 14% in winter. The average blue water footprint of the Parklands calculates 0.66 m3 per square meter per annum. The hot and dry summer causes a high total water footprint compared to the cold and wet winter. This study is transferable to other cities for quantification of blue water consumption of urban green spaces and their water footprint. These findings may help to guide urbanisation priorities to move toward greening cities with no extra pressure on scarce water resources.

China is working hard to reconcile growing demands for freshwater with already oversubscribed renewable water resources. However, the knowledge essential for setting and achieving the intended water consumption cuts remains limited. Here we show that on-farm water management interventions such as improved irrigation and soil management practices for maize cultivation can lead to substantial water consumption reductions, by a simulated total of 28–46 % (7–14 billion m3/year) nationally, with or without the impacts of climate change. The water consumption cut is equivalent to 16–31 % of the ultimate capacity of the South-North Water Transfer Project. Much of the reduction is achievable at the populous and water-stressed North China Plain and Northeast China. Meanwhile, the interventions can increase maize production by an estimated 7–15 %, meeting 22–28 % of demand increase projected for 2050. The water management and food production improvements obtained are crucial for achieving multiple Sustainable Development Goals (SDGs) related to water, land, and food in China and far beyond. © 2019 The Authors

Increased water demand and overexploitation of limited freshwater resources lead to water scarcity, economic downturn, and conflicts over water in many places around the world. A sensible policy measure to bridle humanity's water footprint, then, is to set local and time‐specific water footprint caps, to ensure that water appropriation for human uses remains within ecological boundaries. This study estimates—for all river basins in the world—monthly blue water flows that can be allocated to human uses, while explicitly earmarking water for nature. Addressing some implications of temporal variability, we quantify trade‐offs between potentially violating environmental flow requirements versus underutilizing available flow—a trade‐off that is particularly pronounced in basins with a high seasonal and interannual variability. We discuss several limitations and challenges that need to be overcome if setting water footprint caps is to become a practically applicable policy instrument, including the need (for policy makers) to reach agreement on which specific capping procedure to follow. We conclude by relating local and time‐specific water footprint caps to the planetary boundary for freshwater use., Key Points Overexploitation of freshwater resources shows humanity's current inability to live within the means of the planet in terms of water useWe propose setting water footprint caps per river basin to ensure human water appropriation remains within ecological boundariesWe relate local and time‐specific water footprint caps to the planetary boundary for freshwater use

Water-stressed countries need to plan their food security and reduce the pressure on their limited water resources. Agriculture, the largest water-using sector, has a major role in addressing water scarcity and food security challenges. While there has been quite some attention to water management solutions like soil mulching and improved irrigation, less attention has been paid to adapting the cropping pattern to save water. Here, we investigate how a change in which crops are grown where and when can influence the green and blue water footprint (WF) of crop production, save blue water, reduce blue water scarcity and increase both food and cash crop production, using FAO's AquaCrop model. The performance of two potential solutions, first a strategy of mulching plus drip irrigation, and second a strategy with changing the cropping pattern in addition to mulching and drip irrigation, were compared in one of the most water-stressed catchments in the world, the Upper Litani Basin in Lebanon. Our results show a substantial potential for more efficient use of green water resources for food production while saving scarce blue water resources. Whereas mulching and drip irrigation together decrease the blue WF in the basin by 4.5%, changing the cropping pattern as well can decrease it by 20.3%. Food and cash production could increase by 3% and 50% by changing the cropping pattern, compared to 1.5% and 2.1% by mulching and drip irrigation. Changing the cropping pattern could thus significantly reduce water scarcity and enlarge food and cash production in the basin. © 2020 Authors are thankful for the support from the UN-FAO headquarter and FAO-Lebanon. The ground data used for the simulation and modelling were collected during the field visit of the Litani Basin funded by the FAO-WaPOR project (FRAME consortium)

Environmental contamination with pharmaceuticals is widespread, inducing risks to both human health and the environment. This paper explores potential societal solutions to human and veterinary pharmaceuticals in the aquatic environment. To this end, we adopt transition research’s multi-level perspective framework, which allows us to understand the dynamics underlying pharmaceutical emissions and to recognize social and technical factors triggering change. Our qualitative analysis is based on data collected through literature research and interviews with actors from pharmaceutical industry, the health and agricultural sector. The research aims at identifying potential future solutions including requirements for as well as barriers to pathways leading to these solutions and describing the role of key actors involved. The three alternative societal solutions identified are: 1) accepting pharmaceuticals in the environment - substantial changes to the system are not required; 2) reconfiguring the current system by implementing various innovations that reduce pharmaceutical emissions; 3) fundamentally changing the current system to (largely) avoid pharmaceutical emissions. The paper further elicits societal, financial, organizational, regulatory and technological requirements that can facilitate implementation of these solutions. This work is novel as it constitutes a systemic view on all stages of the pharmaceutical lifecycle, comprehensively synthesizing options and measures along the entire lifecycle into societal solutions that are framed as transition pathways. Deriving societal solutions from key actor’s perspectives is innovative and provides insights to reflect on choices societies are going to have to make regarding pharmaceuticals in the environment. The authors gratefully thank interviewees who allocated time to answer interview questions, shared valuable insights and expressed opinions. Thanks to G. Niebaum for feedback after a trial interview and to E. Aukes for methodological advice. Brugnach’s contribution was partially supported by the Spanish Government’s María de Maeztu excellence accreditation (Ref. MDM-2017-0714 ). The authors acknowledge funding by the European Regional Development fund of the European Union under the INTERREG project MEDUWA-Vecht(e) (project number 142118).

At a spatial resolution level of 5 by 5 arc minute, we estimate anthropogenic nitrogen (N) loads to freshwater, globally. The global anthropogenic N load to freshwater systems from diffuse and point sources in the period 2002–2010 was 32.6 million tonnes per year. China contributed about 45% to this global anthropogenic N load. The USA was the second largest contributor (7%), followed by Russia (6%) and India (5%). Three quarters of the N loads came from diffuse sources (agriculture), 23% from domestic point sources and 2% from industrial point sources. Among the crops, production of cereals had the largest contribution to the N loads (18%, of which 7% wheat and 6% maize), followed by vegetables (15%) and oil crops (11%). It is estimated that, globally, 18% of the total N input on crop fields in the form of artificial fertilizer and manure leaches to freshwater systems.

Agriculture is the largest water user and the driving force behind global water stress. While several studies have already assessed global green and blue water use in crop production at high spatial resolution, few studies have explicitly linked water scarcity to water use in the production of individual crops and assessed the sustainability of each crop production. We provide a detailed assessment of the sustainability and efficiency of the blue water use in global crop production. The study shows that 57% of the global blue WF is unsustainable. Close to 70% of the unsustainable portion of global blue WF is due to the production of five crops: wheat (27%), rice (17%), cotton (10%), sugarcane (8%), and fodder (7%). These crops have large unsustainable blue WF fraction ranging from 43% for rice to 68% for wheat. Countries with a significant proportion of unsustainable blue WF associated with crop production are primarily found in the Middle East and Central Asia. Qatar is at the top of the list, with about 71% of its blue WF being unsustainable, followed by Uzbekistan (68%), Pakistan (68%), and Turkmenistan (67%). Approximately 25% of the blue water can be saved globally by reducing the crop-specific WF to benchmark level.

In Table 2, the unit for nitrogen, phosphate, and potash should have been Mg instead of g (Figure Presented).

Although corporate social responsibility in general and corporate water stewardship specifically are of increasing concern to businesses, investors are lagging behind in fostering water sustainable investment practices – despite the large impact their investment decisions have on the state and shape of tomorrow's water resources. This paper is the first-ever study to assess whether and how investors include water sustainability criteria in their investment decisions, by scrutinizing their publicly released policies on the topic. We hereto (1) developed an assessment framework using the water footprint concept, (2) applied it to twenty large investors in a case study for the Netherlands, and (3) ranked them accordingly. We found that, by and large, water sustainability is a blind spot to investors, resulting in disclosed policies being neither well-demarcated nor clearly formulated, especially regarding the supply chain of the activities invested in. There is a long way to go before investors can ensure efficient, sustainable and fair water use in their investment policy, but our framework helps investors direct their urgently needed improvement process, to transition toward water sustainable production systems in a circular economy.

The formulation of water footprint (WF) benchmarks in crop production – i.e. identifying reference levels of reasonable amounts of water consumption and pollution per tonne of crop produced – has been suggested as a promising strategy to counter inefficient water use and pollution. The current study is the first to show how setting WF benchmarks may help alleviate groundwater scarcity and pollution, in a case study for Iran. We advance the field of WF assessment by developing WF benchmark levels for crop production, which we successively use to assess potential groundwater saving, quality improvement and economic water productivity gains. First, we calculate climate-specific WF benchmark levels for both total blue water footprints and nitrogen-related grey groundwater footprints for 26 crops, for all years in the period 1980–2010, at 5 × 5′ spatial resolution. Second, we estimate the water saving potential for total blue water resources and for groundwater resources specifically, as well as the grey groundwater footprint reduction potential. Finally, we compare mean economic water productivities of crop production in the past with productivities if WFs are reduced to benchmark levels. We find that groundwater comprises up to 83% of total blue water consumption of irrigated crops, with the highest share in arid areas and in cereals. Aquifers are under significant to severe stress, except in the dry sub-humid zone, where irrigation mainly relies on surface water. Reducing WFs of crops to 25th percentile benchmark levels can save 32% of groundwater compared to the reference year 2010, and lower the nitrogen-related grey groundwater footprint by 23%. Moreover, it would increase average economic groundwater productivity in Iran by 20% for cereals, and 59% for nuts. We conclude that reducing WFs to climate-specific benchmark levels in a water-stressed country is a promising way to alleviate overexploitation of aquifers and increase national food security.

This paper introduces a modeling framework for the analysis of real and virtual water flows at national scale. The framework has two components: (1) a national water model that simulates agricultural, industrial and municipal water uses, and available water and land resources; and (2) an international virtual water trade model that captures national virtual water exports and imports related to trade in crops and animal products. This National Water, Food & Trade (NWFT) modeling framework is applied to Egypt, a water-poor country and the world's largest importer of wheat. Egypt's food and water gaps and the country's food (virtual water) imports are estimated over a baseline period (1986–2013) and projected up to 2050 based on four scenarios. Egypt's food and water gaps are growing rapidly as a result of steep population growth and limited water resources. The NWFT modeling framework shows the nexus of the population dynamics, water uses for different sectors, and their compounding effects on Egypt's food gap and water self-sufficiency. The sensitivity analysis reveals that for solving Egypt's water and food problem non-water-based solutions like educational, health, and awareness programs aimed at lowering population growth will be an essential addition to the traditional water resources development solution. Both the national and the global models project similar trends of Egypt's food gap. The NWFT modeling framework can be easily adapted to other nations and regions., Graphical abstract Unlabelled Image, Highlights • Virtual water trade should be considered when managing national water resources. • Non-water based solutions can remediate water problems in water-scarce countries. • Egypt's water and food gaps are projected to aggressively widen in the future. • Both the global and national models projected similar patterns of Egypt's imports. • NWFT modeling framework can be easily applied to any country in the world.

This paper analyzed the impact of land use and its spatial configuration on streamflow in the Samin catchment (278 km2), Indonesia. Historic land use was reconstructed based on satellite images for the years 1982, 1994, 2000, 2006, and 2013. A calibrated and validated Soil and Water Assessment Tool (SWAT) simulated the catchment hydrology of the study area, taking respective land use covers as inputs. A correlation analysis between changes in land use covers and simulated streamflow characteristics was carried out. A land-cover scenario analysis assessed the sensitivity of streamflow characteristics to different future land use covers. The results show that an increase in the settlement connectivity can result in an increase in the ratio of surface runoff to streamflow and a decrease in the ratio of dry-season streamflow to wet-season streamflow, and vice versa. The results suggest that land use pattern management can be an important component in water management.

Hydrological response to expected future changes in land use and climate in the Samin catchment (278 km2) in Java, Indonesia, was simulated using the Soil and Water Assessment Tool model. We analysed changes between the baseline period 1983–2005 and the future period 2030–2050 under both land-use change and climate change. We used the outputs of a bias-corrected regional climate model and six global climate models to include climate model uncertainty. The results show that land-use change and climate change individually will cause changes in the water balance components, but that more pronounced changes are expected if the drivers are combined, in particular for changes in annual streamflow and surface runoff. The findings of this study will be useful for water resource managers to mitigate future risks associated with land-use and climate changes in the study catchment.

For centuries, humans have resorted to building dams to gain control over freshwater available for human consumption. Although dams and their reservoirs have made many important contributions to human development, they receive negative attention as well, because of the large amounts of water they can consume through evaporation. We estimate the blue water footprint of the world's artificial reservoirs and attribute it to the purposes hydroelectricity generation, irrigation water supply, residential and industrial water supply, flood protection, fishing and recreation, based on their economic value. We estimate that economic benefits from 2235 reservoirs included in this study amount to 265 × 109 US$ a year, with residential and industrial water supply and hydroelectricity generation as major contributors. The water footprint associated with these benefits is the sum of the water footprint of dam construction (

The United States is the largest producer of goods and services in the world. Rainfall, surface water supplies, and groundwater aquifers represent a fundamental input to economic production. Despite the importance of water resources to economic activity, we do not have consistent information on water use for specific locations and economic sectors. A national, spatially detailed database of water use by sector would provide insight into U.S. utilization and dependence on water resources for economic production. To this end, we calculate the water footprint of over 500 food, energy, mining, services, and manufacturing industries and goods produced in the United States. To do this, we employ a data intensive approach that integrates water footprint and input‐output techniques into a novel methodological framework. This approach enables us to present the most detailed and comprehensive water footprint analysis of any country to date. This study broadly contributes to our understanding of water in the U.S. economy, enables supply chain managers to assess direct and indirect water dependencies, and provides opportunities to reduce water use through benchmarking. In fact, we find that 94% of U.S. industries could reduce their total water footprint more by sourcing from more water‐efficient suppliers in their supply chain than they could by converting their own operations to be more water‐efficient.

Growing water demands put increasing pressure on local water resources, especially in water-short countries. Virtual water trade can play a key role in filling the gap between local demand and supply of water-intensive commodities. This study aims to analyse the dynamics in virtual water trade of Tunisia in relation to environmental and socio-economic factors such as GDP, irrigated land, precipitation, population and water scarcity. The water footprint of crop production is estimated using AquaCrop for six crops over the period 1981–2010. Net virtual water import (NVWI) is quantified at yearly basis. Regression models are used to investigate dynamics in NVWI in relation to the selected factors. The results show that NVWI during the study period for the selected crops is not influenced by blue water scarcity. NVWI correlates in two alternative models to either population and precipitation (model I) or to GDP and irrigated area (model II). The models are better in explaining NVWI of staple crops (wheat, barley, potatoes) than NVWI of cash crops (dates, olives, tomatoes). Using model I, we are able to explain both trends and inter-annual variability for rain-fed crops. Model II performs better for irrigated crops and is able to explain trends significantly; no significant relation is found, however, with variables hypothesized to represent inter-annual variability.

We estimate the global anthropogenic phosphorus (P) loads to freshwater and the associated grey water footprints (GWFs) for the period 2002–2010, at a spatial resolution of 5 × 5 arc min, and compare the GWF per river basin to runoff to assess the P-related water pollution level (WPL). The global anthropogenic P load to freshwater systems from both diffuse and point sources is estimated at 1.5 Tg/yr. More than half of this total load was in Asia, followed by Europe (19%) and Latin America and the Caribbean (13%). The domestic sector contributed 54% to the total, agriculture 38%, and industry 8%. In agriculture, cereals production had the largest contribution to the P load (31%), followed by fruits, vegetables, and oil crops, each contributing 15%. The global total GWF related to anthropogenic P loads is estimated to be 147 × 10 12 m 3/yr, with China contributing 30%, India 8%, USA 7%, and Spain and Brazil 6% each. The basins with WPL > 1 (where GWF exceeds the basin's assimilation capacity) together cover about 38% of the global land area, 37% of the global river discharge, and provide residence to about 90% of the global population.

Global food trade entails virtual flows of agricultural resources and pollution across countries. Here we performed a global-scale assessment of impacts of international food trade on blue water use, total water use, and nitrogen (N) inputs and on N losses in maize, rice, and wheat production. We simulated baseline conditions for the year 2000 and explored the impacts of an agricultural intensification scenario, in which low-input countries increase N and irrigation inputs to a greater extent than high-input countries. We combined a crop model with the Global Trade Analysis Project model. Results show that food exports generally occurred from regions with lower water and N use intensities, defined here as water and N uses in relation to crop yields, to regions with higher resources use intensities. Globally, food trade thus conserved a large amount of water resources and N applications, and also substantially reduced N losses. The trade-related conservation in blue water use reached 85 km3 y−1, accounting for more than half of total blue water use for producing the three crops. Food exported from the USA contributed the largest proportion of global water and N conservation as well as N loss reduction, but also led to substantial export-associated N losses in the country itself. Under the intensification scenario, the converging water and N use intensities across countries result in a more balanced world; crop trade will generally decrease, and global water resources conservation and N pollution reduction associated with the trade will reduce accordingly. The study provides useful information to understand the implications of agricultural intensification for international crop trade, crop water use and N pollution patterns in the world.

Hydrological models often require input data on soil-water retention (SWR), but obtaining such data is laborious and costly so that SWR in many places remains unknown. To fill the gap, a prediction of SWR using a pedotransfer function (PTF) is one of the alternatives. This study aims to select the most suitable existing PTFs in order to predict SWR for the case of the upper Bengawan Solo (UBS) catchment on Java, Indonesia. Ten point PTFs and two continuous PTFs, which were developed from tropical soils elsewhere, have been applied directly and recalibrated based on a small soil sample set in UBS. Scatter plots and statistical indices of mean error (ME), root mean square error (RMSE), model efficiency (EF) and Pearson’s correlation (r) showed that recalibration using the Shuffled Complex Evolution-University of Arizona (SCE-UA) algorithm can help to improve the prediction of PTFs significantly compared to direct application of PTFs. This study is the first showing that improving SWR-PTFs by recalibration for a new catchment based on around 50 soil samples provides an effective parsimonious alternative to developing a SWR-PTF from specifically collected soil datasets, which typically needs around 100 soil samples or more.

This paper presents the first estimate of global water use in the forestry sector related to roundwood production for lumber, pulp, paper, fuel and firewood. For the period 1961–2010, we estimate forest evaporation at a high spatial resolution level and attribute total water consumption to various forest products, including ecosystem services. Global water consumption for roundwood production increased by 25% over 50 years to 961 × 109 m3/y (96% green; 4% blue) in 2001–2010. The water footprint per m3 of wood is significantly smaller in (sub)tropical forests compared to temperate/boreal forests, because (sub)tropical forests host relatively more value next to wood production in the form of other ecosystem services. In terms of economic water productivity and energy yield from bio-ethanol per unit of water, roundwood is rather comparable with major food, feed and energy crops. Recycling of wood products could effectively reduce the water footprint of the forestry sector, thereby leaving more water available for the generation of other ecosystem services. Intensification of wood production can only reduce the water footprint per unit of wood if the additional wood value per ha outweighs the loss of value of other ecosystem services, which is often not the case in (sub)tropical forests. The results of this study contribute to a more complete picture of the human appropriation of water, thus feeding the debate on water for food or feed versus energy and wood.

Changes in the stream flow of the Samin catchment (277.9 km2) in Java, Indonesia, have been attributed to land use change and climate change. Hydroclimatic data covering the period 1990–2013 and land use data acquired from Landsat satellite imageries for the years 1994 and 2013 were analysed. A quantitative measure is developed to attribute stream flow changes to land use and climate changes based on the changes in the proportion of excess water relative to changes in the proportion of excess energy. The results show that 72% of the increase in stream flow might be attributed to land use change. The results are validated by a land use change analysis and two statistical trend analyses namely the Mann-Kendall trend analysis and Sen's slope estimator for mean annual discharge, rainfall and potential evapotranspiration. The results of the statistical trend analysis are in the same direction as the results of the attribution analysis, where climate change was relatively minor compared to significant land uses change due to deforestation during the period 1994–2013. We conclude that changes in stream flow can be mainly attributed to land use change rather than climate change for the study catchment.

Reducing the water footprint (WF) of the process of growing irrigated crops is an indispensable element in water management, particularly in water-scarce areas. To achieve this, information on marginal cost curves (MCCs) that rank management packages according to their cost-effectiveness to reduce the WF need to support the decision making. MCCs enable the estimation of the cost associated with a certain WF reduction target, e.g. towards a given WF permit (expressed in m3  ha−1 per season) or to a certain WF benchmark (expressed in m3  t−1 of crop). This paper aims to develop MCCs for WF reduction for a range of selected cases. AquaCrop, a soil-water-balance and crop-growth model, is used to estimate the effect of different management packages on evapotranspiration and crop yield and thus the WF of crop production. A management package is defined as a specific combination of management practices: irrigation technique (furrow, sprinkler, drip or subsurface drip); irrigation strategy (full or deficit irrigation); and mulching practice (no, organic or synthetic mulching). The annual average cost for each management package is estimated as the annualized capital cost plus the annual costs of maintenance and operations (i.e. costs of water, energy and labour). Different cases are considered, including three crops (maize, tomato and potato); four types of environment (humid in UK, sub-humid in Italy, semi-arid in Spain and arid in Israel); three hydrologic years (wet, normal and dry years) and three soil types (loam, silty clay loam and sandy loam). For each crop, alternative WF reduction pathways were developed, after which the most cost-effective pathway was selected to develop the MCC for WF reduction. When aiming at WF reduction one can best improve the irrigation strategy first, next the mulching practice and finally the irrigation technique. Moving from a full to deficit irrigation strategy is found to be a no-regret measure: it reduces the WF by reducing water consumption at negligible yield reduction while reducing the cost for irrigation water and the associated costs for energy and labour. Next, moving from no to organic mulching has a high cost-effectiveness, reducing the WF significantly at low cost. Finally, changing from sprinkler or furrow to drip or subsurface drip irrigation reduces the WF, but at a significant cost.

The depletion of water resources, in terms of both quantity and quality, has become a major concern both locally and globally. Ruminants, in particular, are under increased public scrutiny due to their relatively high water use per unit of meat or milk produced. Estimating the water footprint of livestock production is a relatively new field of research for which methods are still evolving. This review describes the approaches used to quantify water use in ruminant production systems as well as the methodological and conceptual issues associated with each approach. Water use estimates for the main products from ruminant production systems are also presented, along with possible management strategies to reduce water use. In the past, quantifying water withdrawal in ruminant production focused on the water demand for drinking or operational purposes. Recently, the recognition of water as a scarce resource has led to the development of several methodologies including water footprint assessment, life cycle assessment, and livestock water productivity to assess water use and its environmental impacts. These methods differ with respect to their target outcome (efficiency or environmental impacts), geographic focus (local or global), description of water sources (green, blue, and gray), handling of water quality concerns, the interpretation of environmental impacts, and the metric by which results are communicated (volumetric units or impact equivalents). Ruminant production is a complex activity where animals are often reared at different sites using a range of resources over their lifetime. Additional water use occurs during slaughter, product processing, and packaging. Estimating water use at the various stages of meat and milk production and communicating those estimates will help producers and other stakeholders identify hotspots and implement strategies to improve water use efficiency. Improvements in ruminant productivity (i.e., BW and milk production) and reproductive efficiency can also reduce the water footprint per unit product. However, given that feed production makes up the majority of water use by ruminants, research and development efforts should focus on this area. More research and clarity are needed to examine the validity of assumptions and possible trade-offs between ruminants' water use and other sustainability indicators.

Summarization: Bioenergy is the most widely used type of renewable energy. A drawback of crops applied for bioenergy is that they compete with food and use the same natural resources like water. From a natural resources perspective, it would be more efficient to apply the large potential of available crop residues. In this paper, we calculate the water footprint (WF) of ten crop residue types and a few other second-generation bioenergy feedstocks (miscanthus, eucalyptus and pine). Further we estimate the WF of energy carriers produced through different conversion techniques (heat or electricity from combustion and gasification, bioethanol from fermentation and oil from pyrolysis), using the global WF standard. The WFs of crop residues, miscanthus and wood show a large variation. Crop residues have a smaller WF than miscanthus and wood. Given a certain feedstock, the WF of pyrolysis oil is smaller than the WF of bioethanol from fermentation. The WFs of heat from combustion or gasification are similar. The WF of electricity by combustion ranges from 33 to 324 m3/GJ and the WF of electricity by gasification from 21 to 104 m3/GJ. This research concludes that it is relatively water-efficient to apply crop residues, and that the production of miscanthus and wood for bioenergy is less favourable. Crop residues can best be converted to oil rather than to ethanol. Electricity from gasification has a smaller WF than electricity form combustion; heat from combustion has a smaller WF than heat from gasification. By showing the water efficiency of different feedstocks and techniques to produce second-generation bioenergy, the study provides a useful basis to wisely choose amongst different alternative forms of second-generation bioenergy. Presented on: Journal of Cleaner Production

Meat production puts larger demands on water and land and results in larger greenhouse gas emissions than alternative forms of food. This study uses footprint indicators, the water, land and carbon footprint, to assess natural resources use and greenhouse gas emissions for sheep and chicken meat produced in Tunisia in different farming systems in the period 1996–2005. Tunisia is a water-scarce country with large areas of pasture for sheep production. Poultry production is relatively large and based on importedfeed. The farming systems considered are: the industrial system for chicken, and the agro-pastoral system using cereal crop-residues, the agro-pastoral system using barley and the pastoral system using barley for sheep. Chicken meat has a smaller water footprint (6030 litre/kg), land footprint (9 m2/kg) and carbonfootprint (3 CO2-eq/kg) than sheep meat (with an average water footprint of 18900 litre/kg, land footprint of 57 m2/kg, and carbon footprint of 28 CO2-eq/kg). For sheep meat, the agro-pastoral system using cereal crop-residues is the production system with smallest water and land footprints, but the highest carbon footprint. The pastoral system using barley has larger water and land footprints than the agro-pastoral system using barley, but comparable carbon footprint.

Water pollution by pharmaceuticals is widespread, causing both environmental and human health risks. We assess pharmaceutical water pollution from human and veterinary pharmaceuticals at three geographical levels: global, national (considering Germany and the Netherlands) and catchment level (with a case study for the Vecht catchment shared by Germany and the Netherlands). The grey water footprint (GWF), a measure of water pollution in volumetric terms, is estimated from pharmaceutical loads entering the aquatic environment, considering different pollutant sources and pathways. We study different substances depending on data availability, which varies across geographical levels. Results show a global per capita GWF of 1900 m3 yr−1 resulting from human consumption of ciprofloxacin. The largest GWFs in both Germany and the Netherlands were found for ethinylestradiol for human and amoxicillin for veterinary use. The estimated per capita GWF from human use of ethinylestradiol is 2300 m3 yr−1 for Germany and 11,300 m3 yr−1 for the Netherlands. The per capita GWFs of German and Dutch consumers of animal products are 12,900 and 10,600 m3 yr−1, respectively. For the Vecht catchment, we estimate the water pollution level per sub-catchment by comparing the GWF to available runoff, which enables us to identify geographic hotspots. In the basin as a whole, GWFs from human and veterinary pharmaceuticals both exceed available runoff. At all levels, pharmaceutical water pollution substantially adds to earlier water footprint studies that excluded this type of pollution, which demonstrates the importance to include pharmaceutics in water footprint studies., Highlights • This is the first broad study on grey water footprint (GWF) of pharmaceuticals. • Human and veterinary compounds are included and three spatial levels assessed. • GWFs of pharmaceuticals are substantial compared to GWFs of other pollutants. • Animal products add a substantial part to consumer’s pharmaceutical-related GWF. • Grey water footprints exceed available runoff in a case study for the Vecht basin.

Feeding a growing population with global natural resource constraints becomes an increasingly challenging task. Changing spatial cropping patterns and international crop trade could contribute to sustain crop production and mitigate water scarcity. Previous studies on water saving through international food trade focussed either on comparing water productivities among food-trading countries or on analysing food trade in relation to national water endowments. Here, we consider, for the first time, how both differences in water productivities and water endowments can be considered to analyse comparative advantages of countries for different types of crop production. A linear optimization algorithm is used to find modifications in global cropping patterns that reduce blue water scarcity in the world's hotspots, under the constraint of current global production per crop and current cropland areas. The optimization considers national water and land endowments as well as water and land productivity per country per crop. The results are used to assess national comparative advantages and disadvantages for different crops. When allowing a maximum expansion of harvested area per crop per country of 10 %, the blue water scarcity in the world's most water-scarce countries can be greatly reduced. In this case, we could achieve a reduction of the current blue water footprint of crop production in the world of 9 % and a decrease of global total harvested area of 4 %.

The development of ‘greening’ cities introduces an uneasy tension between more green spaces and the increased use of scarce blue water resources to maintain this greenness, particularly in dry regions. This paper presents the first estimate of the blue water footprint (WF) of urban greenery. We estimated total water consumption of a 10-hectare parkland in Adelaide, South Australia. Evapotranspiration of the urban vegetation was estimated by monitoring soil water inflows, outflows, and storage changes at an experimental site representing different species, microclimates, and plant densities, the most critical parameters affecting water use. The total WF was estimated at 11,140 m3/ha per year, 59% from blue water (irrigation), and 41% from green water (rainwater), with the highest water consumption in summer. The dependency on blue water resources for maintaining the greenery varied from 49% in October to 67% in March. Even in the wet period of the year, there was a significant blue WF. Given the lack of blue water resources to allocate for further greening the city in an arid environment, we suggest an integrated adaptive management strategy to maintain available greenery and expand green spaces with a minimum of extra pressure on blue water resources. peerReviewed