Arjen Ysbert Hoekstra

The water footprint assessment manual : setting the global standard

This manual presents a scientifically rigorous method to help companies understand their dependency and impact on global water resources, and offers guidance on response strategies that conserve water for industry, communities, and nature. It contains the global standard for water footprint assessment as developed and maintained by the Water Footprint Network. It covers a comprehensive set of definitions and methods for water footprint accounting. It shows how water footprints are calculated for individual processes and products, as well as for consumers, nations, and businesses. It also includes methods for water footprint sustainability assessment and a library of water footprint response options. The water footprint of a product is the volume of freshwater used to produce the product, measured over the fully supply chain. It is a multidimensional indicator, showing water consumption volumes by source and polluted volumes by type of pollution; all components of a total water footprint are specified geographically and temporally.

The water footprint of humanity

This study quantifies and maps the water footprint (WF) of humanity at a high spatial resolution. It reports on consumptive use of rainwater (green WF) and ground and surface water (blue WF) and volumes of water polluted (gray WF). Water footprints are estimated per nation from both a production and consumption perspective. International virtual water flows are estimated based on trade in agricultural and industrial commodities. The global annual average WF in the period 1996–2005 was 9,087 Gm3/y (74% green, 11% blue, 15% gray). Agricultural production contributes 92%. About one-fifth of the global WF relates to production for export. The total volume of international virtual water flows related to trade in agricultural and industrial products was 2,320 Gm3/y (68% green, 13% blue, 19% gray). The WF of the global average consumer was 1,385 m3/y. The average consumer in the United States has a WF of 2,842 m3/y, whereas the average citizens in China and India have WFs of 1,071 and 1,089 m3/y, respectively. Consumption of cereal products gives the largest contribution to the WF of the average consumer (27%), followed by meat (22%) and milk products (7%). The volume and pattern of consumption and the WF per ton of product of the products consumed are the main factors determining the WF of a consumer. The study illustrates the global dimension of water consumption and pollution by showing that several countries heavily rely on foreign water resources and that many countries have significant impacts on water consumption and pollution elsewhere.

The water footprint of bioenergy

All energy scenarios show a shift toward an increased percentage of renewable energy sources, including biomass. This study gives an overview of water footprints (WFs) of bioenergy from 12 crops that currently contribute the most to global agricultural production: barley, cassava, maize, potato, rapeseed, rice, rye, sorghum, soybean, sugar beet, sugar cane, and wheat. In addition, this study includes jatropha, a suitable energy crop. Since climate and production circumstances differ among regions, calculations have been performed by country. The WF of bioelectricity is smaller than that of biofuels because it is more efficient to use total biomass (e.g., for electricity or heat) than a fraction of the crop (its sugar, starch, or oil content) for biofuel. The WF of bioethanol appears to be smaller than that of biodiesel. For electricity, sugar beet, maize, and sugar cane are the most favorable crops [50 m3/gigajoule (GJ)]. Rapeseed and jatropha, typical energy crops, are disadvantageous (400 m3/GJ). For ethanol, sugar beet, and potato (60 and 100 m3/GJ) are the most advantageous, followed by sugar cane (110 m3/GJ); sorghum (400 m3/GJ) is the most unfavorable. For biodiesel, soybean and rapeseed show to be the most favorable WF (400 m3/GJ); jatropha has an adverse WF (600 m3/GJ). When expressed per L, the WF ranges from 1,400 to 20,000 L of water per L of biofuel. If a shift toward a greater contribution of bioenergy to energy supply takes place, the results of this study can be used to select the crops and countries that produce bioenergy in the most water-efficient way.

Global Monthly Water Scarcity: Blue Water Footprints versus Blue Water Availability

Freshwater scarcity is a growing concern, placing considerable importance on the accuracy of indicators used to characterize and map water scarcity worldwide. We improve upon past efforts by using estimates of blue water footprints (consumptive use of ground- and surface water flows) rather than water withdrawals, accounting for the flows needed to sustain critical ecological functions and by considering monthly rather than annual values. We analyzed 405 river basins for the period 1996–2005. In 201 basins with 2.67 billion inhabitants there was severe water scarcity during at least one month of the year. The ecological and economic consequences of increasing degrees of water scarcity – as evidenced by the Rio Grande (Rio Bravo), Indus, and Murray-Darling River Basins – can include complete desiccation during dry seasons, decimation of aquatic biodiversity, and substantial economic disruption.

A global assessment of the Water Footprint of Farm Animal Products

The increase in the consumption of animal products is likely to put further pressure on the world’s freshwater resources. This paper provides a comprehensive account of the water footprint of animal products, considering different production systems and feed composition per animal type and country. Nearly one-third of the total water footprint of agriculture in the world is related to the production of animal products. The water footprint of any animal product is larger than the water footprint of crop products with equivalent nutritional value. The average water footprint per calorie for beef is 20 times larger than for cereals and starchy roots. The water footprint per gram of protein for milk, eggs and chicken meat is 1.5 times larger than for pulses. The unfavorable feed conversion efficiency for animal products is largely responsible for the relatively large water footprint of animal products compared to the crop products. Animal products from industrial systems generally consume and pollute more ground- and surface-water resources than animal products from grazing or mixed systems. The rising global meat consumption and the intensification of animal production systems will put further pressure on the global freshwater resources in the coming decades. The study shows that from a freshwater perspective, animal products from grazing systems have a smaller blue and grey water footprint than products from industrial systems, and that it is more water-efficient to obtain calories, protein and fat through crop products than animal products.

Four billion people facing severe water scarcity

Global water scarcity assessment at a high spatial and temporal resolution, accounting for environmental flow requirements. Freshwater scarcity is increasingly perceived as a global systemic risk. Previous global water scarcity assessments, measuring water scarcity annually, have underestimated experienced water scarcity by failing to capture the seasonal fluctuations in water consumption and availability. We assess blue water scarcity globally at a high spatial resolution on a monthly basis. We find that two-thirds of the global population (4.0 billion people) live under conditions of severe water scarcity at least 1 month of the year. Nearly half of those people live in India and China. Half a billion people in the world face severe water scarcity all year round. Putting caps to water consumption by river basin, increasing water-use efficiencies, and better sharing of the limited freshwater resources will be key in reducing the threat posed by water scarcity on biodiversity and human welfare.

The global component of freshwater demand and supply: an assessment of virtual water flows between nations as a result of trade in agricultural and industrial products

Where the river basin is generally seen as the appropriate unit for analysing freshwater availability and use, this paper shows that it becomes increasingly important to put freshwater issues in a global context. International trade in commodities implies flows of ‘virtual water’ over large distances, where virtual water should be understood as the volume of water required to produce a commodity. Virtual water flows between nations have been estimated from statistics on international product trade and the virtual water content per product in the exporting country. With increasing globalization of trade, global water interdependencies and overseas externalities are likely to increase. At the same time liberalization of trade creates opportunities to increase physical water savings.

Humanity's unsustainable environmental footprint.

Within the context of Earth’s limited natural resources and assimilation capacity, the current environmental footprint of humankind is not sustainable. Assessing land, water, energy, material, and other footprints along supply chains is paramount in understanding the sustainability, efficiency, and equity of resource use from the perspective of producers, consumers, and government. We review current footprints and relate those to maximum sustainable levels, highlighting the need for future work on combining footprints, assessing trade-offs between them, improving computational techniques, estimating maximum sustainable footprint levels, and benchmarking efficiency of resource use. Ultimately, major transformative changes in the global economy are necessary to reduce humanity’s environmental footprint to sustainable levels.

Water in crisis

What do you do to start reading water in crisis? Searching the book that you love to read first or find an interesting book that will make you want to read? Everybody has difference with their reason of reading a book. Actuary, reading habit must be from earlier. Many people may be love to read, but not a book. Its not fault. Someone will be bored to open the thick book with small words to read. In more, this is the real condition. So do happen probably with this water in crisis.

Virtual versus real water transfers within China.

North China faces severe water scarcity—more than 40% of the annual renewable water resources are abstracted for human use. Nevertheless, nearly 10% of the water used in agriculture is employed in producing food exported to south China. To compensate for this ‘virtual water flow’ and to reduce water scarcity in the north, the huge south–north Water Transfer Project is currently being implemented. This paradox—the transfer of huge volumes of water from the water-rich south to the water-poor north versus transfer of substantial volumes of food from the food-sufficient north to the food-deficit south—is receiving increased attention, but the research in this field has not yet reached further than rough estimation and qualitative description. The aim of this paper is to review and quantify the volumes of virtual water flows between the regions in China and to put them in the context of water availability per region. The analysis shows that north China annually exports about 52 billion m3 of water in virtual form to south China, which is more than the maximum proposed water transfer volume along the three routes of the Water Transfer Project from south to north.