Urban Water Footprint Research Articles

Urban water footprint in Mashhad, Iran’s second largest city

Summary The water footprint (WF) is a metric used to quantify the total volume of fresh water consumed directly and indirectly by individuals and communities; it helps to inform responses to global challenges such as water scarcity, climate change and sustainable water management. This study assessed virtual (VWF), direct (DWF) and total (TWF) water footprints in Mashhad, Iran’s second largest city. Data collected from 382 households showed that the average individual VWF was 1314 m3 per month, the average individual DWF was 228 m3 per month and the average individual TWF was 1538 m3 per month. Additionally, key consumption patterns were identified, with rice and bread emerging as the most consumed items and vegetables as the least consumed. Over a 5-year period, direct water use declined. Significant correlations emerged between family size, annual cost and VWF and TWF, yet no association was found between age and the WFs. There were income-based disparities in VWF and TWF but no differences across education levels in terms of DWF, VWF and TWF. These findings offer crucial insights for policymakers and water authorities in formulating effective water-saving policies to address pressing environmental concerns.

Spatial allocation of LID practices with a water footprint approach

Urban water problems due to stormwater have been aggravated by the higher frequency of high-intensity precipitation events and the increase of paved surfaces. However, with appropriate stormwater management practices, such as low-impact development (LID), stormwater can provide an additional urban water resources rather than cause damage. This study aims to apply a water footprint to location determination of LID practices in the urban area. The LID planning procedure was demonstrated with the highest population density region in Taipei, Taiwan. In order to improve the spatial resolution of LID allocation, the “first-level dissemination area” with 450 residents was used as a spatial unit. The performance of LID practices was then evaluated with the simulation using the Storm Water Management Model (SWMM). Three LID practices, rainwater harvesting systems, permeable pavements, and bioretention systems, were selected. After the water footprint accounting, ten sites were suggested for LID implementation. The runoff reduction rate reached up to 65 % by rainwater harvesting systems or at least 3 % by permeable pavements. This study provides a simpler and more effective approach to ways of integrating an urban water footprint into LID planning and stormwater management in urban areas.

An assessment of the urban water footprint and blue water scarcity: A case study for Van (Turkey).

Today, most of the world's population faces water scarcity, while global warming, urbanization, industrialization and population increases continue to increase the severity of the pressure on water resources. Management of water resources plays a key role in the sustainability of agricultural production. The water footprint (WF) is different in comparison to other water statistics because it takes direct and indirect water consumption into account, and helps in the management of water resources. Within this context, the WF of Van province, which is Turkey's most easterly located arid region, was calculated from 2004 to 2019. The study area covers lake Van, which is Turkey's largest lake, and the Van basin with an area of 23.334 km2 and a population of 1.136.757 (2019). In the calculations, crop (WFcrop), livestock (WFlivestock), and domestic and industrial water footprints (WFdomestic+industrial) were evaluated separately, and blue and green water footprints (WFblue and WFgreen) were analyzed in detail. According to the results, the average WF of Van province was found to be 8.73 billion m3 year-1. Throughout the province, 87.6% of the WF is composed of WFcrop, 4.9% is WFlivestock and 7.5% is WFdomestic+industrial. Of the WFcrop, 62.5% depends on WFblue, i.e., freshwater. Most of the WFlivestock consisted of dairy cattle (49%) and sheep (38%). The average WFdomestic+industrial for 2004 to 2019 was 0.64 billion m3 year-1. The average per capita water footprint of Van province was found to be 889.9 m3 year-1 capita-1. In addition, the province is classified as severe water scarcity (257%). This study is one of the first province-based calculations of WF in Turkey and is the first study to bring a different aspect to published literature by including residual soil moisture from the winter months. As a result of this study, the WFblue of the WFcrop is above the worldwide average and should be reduced by changing the crop pattern or synchronizing the planting and harvest dates of the crops to a period that benefits from precipitation. In addition, this study is expected to contribute to new studies for calculating the provincial scale WF and will have positive effects on agricultural planning, water allocation and the sustainability of water resources.

Dynamics of the Urban Water Footprint on the Tibetan Plateau: A Case Study of Xining, China.

Determining the changes in the urban water footprint (WF) of the Tibetan Plateau is important for sustainable development within this region and in downstream regions. Taking Xining, the largest city on the Tibetan Plateau, as an example, this study quantified the changes in the WF of this region in the 2005–2018 period. We found that Xining’s total WF increased by 22.6%, from 8.9 billion to 10.9 billion m3 in this period. The increase in Xining’s gray WF (WFgray) resulting from the intensification of urban point-source pollution was the primary cause of the increase in its total WF. Xining’s WFgray from point-source pollution increased by 75.3%, from 3.1 billion to 5.4 billion m3. In addition, Xining’s WF far surpassed the amount of available water resources (WA) in this region. It is possible to prevent Xining’s WF from exceeding its WA only by simultaneously controlling point- and nonpoint-source pollution in the future. Thus, it is recommended that great importance be attached to the rapid increase in the WFgray of the Tibetan Plateau resulting from rapid urbanization and that effective measures be implemented to control point- and nonpoint-source pollution, so as to safeguard sustainable development within the Tibetan Plateau and in downstream regions.

Blue and grey urban water footprints through citizens’ perception and time series analysis of Brazilian dynamics

ABSTRACT Predicting future water demands of societies is a major challenge because it involves a holistic understanding of possible changes within socio-hydrological systems. Although recent research has made efforts to translate social dimensions into the analysis of hydrological systems, few studies have involved citizen participation in water footprint analysis. This paper integrates time series with citizens’ perceptions, knowledge and beliefs concerning sanitation elements to account for municipal blue and grey water footprints in São Carlos, Brazil, from 2009 to 2016, and potential water footprints in 2030 and 2050. In this case study, grey footprint potentially exceeds the blue water footprint by up to 35 times, and volunteered information suggested a reduction in water consumption, larger garbage production and greater investment in sanitation infrastructure from authorities. We conclude that public knowledge can be used to delineate possible water footprint scenarios and reveal paradoxes in the coevolution of socio-hydrological systems on an urban scale.

Full Domestic Supply Chains of Blue Virtual Water Flows Estimated for Major U.S. Cities

AbstractThrough the trade of products and services, cities indirectly depend on distant water sources to function, prosper, and grow. To fully account for indirect (virtual) water dependencies, virtual water flows need to be known along complex supply chains. To this purpose, we build a new environmental multiregional input–output model for U.S. regions. The model is used to quantify the domestic, blue virtual water flows and analyze the water footprints of 69 major U.S. cities. Our results show a large inequality in the urban water consumed for economic production: just 7 out of the 69 cities included in this study account for 35% of the U.S. national water footprint of production. This is due to the production of water‐intensive agricultural products in the metropolitan areas of western cities. The inequality reduces for the urban water footprint of consumption because, through the supply chains of industrialized food sectors, western virtual water is partially transferred to eastern cities as final demand. The water embodied in industrial products and services tends to be higher in western cities than in eastern cities; that is, the water embodied in food services could be several times higher in Los Angeles than in New York City. Trade hub cities attract large inflows of products which are mostly transformed for consumption elsewhere. Thus, the omission of product interdependencies within trade hub cities can increase by several times their water footprints of consumption. Overall, the proposed model is able to enhance subnational estimates of U.S. virtual water flows.

Large cities get more for less: Water footprint efficiency across the US.

Many urban indicators and functional citywide properties have been shown to scale with population due to agglomeration effects. We hypothesize that scaling relations may also exist for water-related urban indicators such as the water footprint. The water footprint is an indicator of water use that measures humans’ appropriation of freshwater resources. We analyze the scaling of the water footprint for 65 mid- to large-sized US cities using both empirical estimates and a social interaction network model of city functioning. The network model is used to explain the presence of any scaling exponent in the empirical estimates of the urban water footprint by linking to previous theories of urban scaling. We find that the urban water footprint tends to approximately show sublinear scaling behavior with both population and gross domestic product. Thus, large cities tend to be more water footprint efficient and productive than mid-sized cities, where efficiency and productivity are quantified, in a broad sense, as deviations from a linear scaling exponent. We find the sublinear scaling may be linked to changes in urban economic structure with city size, which lead to large cities shifting water intensive economic activities to less populated regions. In addition, we find that green water contributes to the scaling both positively by transferring the dependence of food consumption on population into the water footprint and negatively by increasing heterogeneity. Overall, the proposed scaling relations allow for the comparison of water footprint efficiency and productivity of cities. Comparing these properties and identifying deviations from the expected behavior has implications for water resources and urban sustainability.

Water footprints in Beijing, Tianjin and Hebei: A perspective from comparisons between urban and rural consumptions in different regions

Examination of a region/country's water footprint and its underlying influencing factors is essential for enhancing understanding of water resource problems and challenges. This study addresses the influencing factors that lead to different consumption-based water footprints (WFs) per capita in different countries/regions, with emphasis on differentiating urban and rural WFs and examining the role of urbanization. Structural decomposition analysis, which is conventionally used for investigating temporal changes of an environmental variable, is adapted to inspect the factors shaping spatial difference. This adapted approach breaks down the difference of WFs per capita between provinces into five contributing factors, i.e., urbanization level, direct water use efficiency, production structure, inhabitant consumption level and consumption structure. According to WF accounting based on input-output tables in Beijing, Tianjin and Hebei in the greater capital region of China in 2010, the urban WFs per capita are between 1.6 and 3.7 times the rural WFs. Residential WFs per capita in Beijing, Tianjin and Hebei show a large variability between 114 m3 and 463 m3. The results of the adapted structural decomposition analysis indicate that urbanization and rising consumption levels, which are two foreseeable trends when economic and social conditions improve, result in increasing WF per capita, whereas the direct water use efficiency, economic production structure and consumption structure may contribute to offset the WF. Inhabitant consumption levels dominate other factors resulting in differences of WF per capita between provinces. The results are beneficial for informing policies towards sustainable water resource consumption under the framework of the integrated development of the greater capital region in China.

Decomposition of the Urban Water Footprint of Food Consumption: A Case Study of Xiamen City

Decomposition of the urban water footprint can provide insight for water management. In this paper, a new decomposition method based on the log-mean Divisia index model (LMDI) was developed to analyze the driving forces of water footprint changes, attributable to food consumption. Compared to previous studies, this new approach can distinguish between various factors relating to urban and rural residents. The water footprint of food consumption in Xiamen City, from 2001 to 2012, was calculated. Following this, the driving forces of water footprint change were broken down into considerations of the population, the structure of food consumption, the level of food consumption, water intensity, and the population rate. Research shows that between 2001 and 2012, the water footprint of food consumption in Xiamen increased by 675.53 Mm3, with a growth rate of 88.69%. Population effects were the leading contributors to this change, accounting for 87.97% of the total growth. The food consumption structure also had a considerable effect on this increase. Here, the urban area represented 94.96% of the water footprint increase, driven by the effect of the food consumption structure. Water intensity and the urban/rural population rate had a weak positive cumulative effect. The effects of the urban/rural population rate on the water footprint change in urban and rural areas, however, were individually significant. The level of food consumption was the only negative factor. In terms of food categories, meat and grain had the greatest effects during the study period. Controlling the urban population, promoting a healthy and less water-intensive diet, reducing food waste, and improving agriculture efficiency, are all elements of an effective approach for mitigating the growth of the water footprint.

Direct and indirect urban water footprints of the United States

AbstractThe water footprint of the urban environment is not limited to direct water consumption (i.e., municipal supplies); embedded water in imported resources, or virtual water transfers, provides an additional component of the urban water footprint. Using empirical data, our analysis extends traditional urban water footprinting analysis to quantify both direct and indirect urban resources for the United States. We determine direct water volumes and their embedded energy through open records requests of water utilities. The indirect component of the urban water footprint includes water indirectly consumed through energy and food, relating to the food‐energy‐water nexus. We comprehensively quantify the indirect water footprint for 74 metropolitan statistical areas through the combination of various databases, including the Commodity Flow Survey of the U.S. Census Bureau, the U.S. Department of Agriculture, the Water Footprint Network, and the Energy Information Administration. We then analyze spatial heterogeneity in both direct and indirect water footprints, determining the average urban water footprint in the United States to be 1.64 million gallons of water per person per year [6200 m3/person/yr or 17,000 L/person/d], dominated by indirect water. Additionally, our study of the urban water cycle extends beyond considering only water resources to include embedded energy and equivalent carbon dioxide emissions. The inclusion of multiple sectors of the urban water cycle and their underlying processes provides important insights to the overall urban environment, the interdependencies of the food‐energy‐water nexus, and water resource sustainability. Our results provide opportunities for benchmarking the urban energy‐water nexus, water footprints, and climate change potential.

Food consumption and related water resources in Nordic cities

Many modern cities have strongly invested in the sustainability of their urban water management system. Nordic cities like Stockholm or Copenhagen are amongst pioneers in investments towards integrated urban water management. However, cities can never be fully self-sufficient due to their dependency on external (water) resources. In this paper, we quantify this water dependency with respect to food consumption in nine cities located in the five Nordic countries (Sweden, Denmark, Finland, Norway and Iceland), by means of the water footprint concept. Detailed urban water footprint assessments are scarce in the literature. By analysing national nutrition surveys, we find that urban food intake behaviour differs from national food intake behaviour. In large Nordic cities people eat generally less potatoes, milk products (without cheese), meat and animal fats and they drink less coffee than outside city borders. On the other hand, they generally eat more vegetables and vegetable oils and they drink more tea and alcoholic beverages. This leads consistently – for the six large Nordic cities Stockholm, Malmö, Copenhagen, Helsinki, Oslo and Reykjavik – to slightly smaller food related urban water footprints (−2 to −6%) than national average values. We also analyse the water footprint for different diets based upon Nordic Nutrition Recommendations (NNR) for these cities. We assessed three healthy diet scenarios: 1) including meat (HEALTHY-MEAT), 2) pesco-vegetarian (HEALTHY-PESCO-VEG) and 3) vegetarian (HEALTHY-VEG). This shows that Nordic urban dwellers 1) eat too many animal products (red meat, milk and milk products) and sugar and drink too much alcohol and 2) they eat not enough vegetables, fruit and products from the group pulses, nuts and oilcrops. Their overall energy and protein intake is too high. A shift to a healthy diet with recommended energy and protein intake reduces the urban WF related to food consumption substantially. A shift to HEALTHY-MEAT results in a reduction of −9 to −24%, for HEALTHY-PESCO-VEG the reduction is −29 to −37%, for HEALTHY-VEG the reduction is −36 to −44%. In other words, Nordic urban dwellers can save a lot of water by shifting to a healthy diet.

Regional Water Footprint Assessment: A Case Study of Leshan City

This paper presents an assessment of urban water footprint in the period of 2001 to 2012 by taking Leshan City, China as a typical case study. The water footprint is calculated by the sum of the water footprints of various sectors, i.e., crop production, animal products, industrial processes, domestic waster, eco-environment, and virtual water trade. Results show that the water footprints of the various sectors rose by degrees varying from 19% to 55%, which gave rise to an increase of the total water footprint of 43.13% from 2001 to 2012. Crop production and animal products are identified as the major water intensive sectors, accounting for about 68.97% of the total water footprint. The water footprint in the Northeastern area of Leshan City is greater than that of the Southwestern area in the period 1992–2012, resulted in an expansion of water footprint in the Sha Wan and Wu Tongqiao Districts due to the development of urbanization. The application of water footprint assessment is expected to provide insight into the improvement of urban water efficiency, and thus aid in better water resources management.

Water Footprint of Cities: A Review and Suggestions for Future Research

Cities are hotspots of commodity consumption, with implications for both local and systemic water resources. Water flows “virtually” into and out of cities through the extensive cross-boundary exchange of goods and services. Both virtual and real water flows are affected by water supply investments and urban planning decisions, which influence residential, commercial, and industrial development. This form of water “teleconnection” is being increasingly recognized as an important aspect of water decision-making. The role of trade and virtual water flows as an alternative to expanding a city’s “real” water supply is rarely acknowledged, with an emphasis placed instead on monotonic expansion of engineering potable water supplies. We perform a literature review of water footprint studies to evaluate the potential and importance of taking virtual flows into account in urban planning and policy. We compare and contrast current methods to assess virtual water flows. We also identify and discuss priorities for future research in urban water footprint analysis.

Ecohydrology of street trees: design and irrigation requirements for sustainable water use

ABSTRACTWhereas the beneficial effects of urban vegetation have long been recognized, growing conditions in urban environments, especially for street trees, are typically harsh and limited by low water availability. Supplemental irrigation may be used to preserve aesthetic quality and ability to provide ecosystem services of urban vegetation but requires careful management of available economic and water resources to reduce urban water footprint. To this purpose, decision makers need quantitative tools, requiring few, physically based parameters and accounting for the uncertainties and future scenarios of the hydroclimatic forcing. Focusing on in‐row and isolated trees, a minimalist description of street tree water balance is proposed here, including rainfed and irrigated conditions, and explicitly accounting for tree water requirements, growing conditions (in terms of soil properties and extension of bare soil, permeable and impervious pavements surrounding the tree) and rainfall unpredictability. The proposed model allows the quantification of tree cooling capacity, water stress occurrence and irrigation requirements, as a function of soil, plant and climate characteristics, thus providing indications regarding the tree ability to provide ecosystem services and management costs. In particular, an analysis of different planting designs suggests that a balanced design consisting in bare soil and permeable pavement with size equal to the lateral canopy extension is optimal for water conservation, tree cooling capacity and health. The proposed model provides useful indications towards the definition of site‐specific guidelines for species selection and planting design, for sustainable urban vegetation. Copyright © 2013 John Wiley & Sons, Ltd.

A global perspective on changing sustainable urban water supplies

Ensuring the sustainable supply of water for the world's largest cities has been and is a current challenge. Future trends in urban water consumption patterns will be determined by changes in population concentration, per-capita water use, climate, and the proportion of water retained for the production of instream ecosystem services. The objective of our research was to identify patterns of renewable water availability and urban consumption throughout the globe between the years 2000 and 2015. To better understand the interactions between urban consumption and regional availability of renewable water we used a modified ecological footprint (EF) approach. Urban water footprint areas were differentially sensitive to changes in consumption and changes in water availability; our results suggest climate induced reductions in water availability may be more of a concern than population growth or increased per-capita for securing continued supplies of water to large cities. Our results provide a comprehensive description of global urban water demand and highlight the variation between consumption and availability relationships for the 524 largest cities.