Grey Water Footprint Research Articles

System dynamics simulation and scenario optimization of China's water footprint under different SSP-RCP scenarios

Under the dual influence of socioeconomic development and climate change, water resources in China are under increasing stress. It is of great significance to comprehensively explore the changing trend of China's water footprint (WF) in the future, clarify the water resource challenges that China will face, and alleviate water shortage and water pollution problems. This paper uses System Dynamics (SD) to build a simulation model of China's WF, calculate China's WF from 2000 to 2019, and for the first time, simulate and optimize China's WF from 2020 to 2050 under the SSP-RCP scenario matrix composed of Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs). The results are as follows. (1) From 2000 to 2019, China's WF increased to 2009 and began to decline. The main contributors are grey WF and agricultural WF. (2) During 2020–2050, China's total WF under the SSP1-2.6 scenario will always be at the lowest; compared with other scenarios, the simulation result of China's total WF under the SSP2-4.5 scenario is the closest to the actual situation in China in 2020, 2021 and 2022. China's total WF under the SSP4-6.0 scenario is close to that under the SSP2-4.5 scenario, but the numerical variation characteristics of the WF composition are different. China's total WF under the SSP3-7.0 and SSP5-8.5 scenarios is high. (3) Based on the changes in WF and water resources supply/demand ratio under different scenarios, the SSP1-2.6 scenario is the best scenario to mitigate a future water shortage and water pollution in China. The research results can help decision-makers formulate relevant management policies and socioeconomic development models for water resource utilization and provide decision support for alleviating water shortages and water pollution in China.

Improved grey water footprint model based on uncertainty analysis

In the practical water resources management, the allowable thresholds of pollutants are not unique. However, the conventional grey water footprint (GWF) model cannot deal with this uncertainty in the controlling threshold. To solve this problem, an improved GWF model and pollution risk evaluation method is designed according to the uncertainty analysis theory and maximum entropy principle. In this model, GWF is defined as the mathematical expectation of virtual water to dilute the pollution load within the allowable threshold, and the pollution risk is deduced by the stochastic probability by which GWF exceeds the local water resources. And then, the improved GWF model is applied in the pollution evaluation of Jiangxi Province, China. The results show that: (1) From 2013 to 2017, the annual GWF values of Jiangxi Province were 136.36 billion m3, 143.78 billion m3, 143.77 billion m3, 169.37 billion m3 and 103.36 billion m3, respectively. And their pollution risk values and grades were 0.30 (moderate), 0.27 (moderate), 0.19 (low), 0.22 (moderate), and 0.16 (low), respectively. In 2015, the determinant of the GWF was TP, and TN in other years. (2) The improved GWF model has an evaluation result which is basically consistent with WQQR, and it is an effective water resource evaluation method to deal with the uncertainty in controlling thresholds. (3) Compared with the conventional GWF model, the improved GWF model has better capacities in identifying pollution grades and recognizing pollution risks.

A multi-pollutant pilot study to evaluate the grey water footprint of irrigated paddy rice

A multi-pollutant pilot study to evaluate the grey water footprint of irrigated paddy rice

Leaching Runoff Fraction for Nitrate and Herbicides on Sugarcane Fields: Implications for Grey Water Footprint

Sugarcane cultivation uses many chemical inputs to ensure good yields, which puts local water resources under pressure. Grey water footprint (GWF) is a widely used indicator of the volume needed to assimilate a pollutant load in a water body. However, the GWF relies on leaching runoff fractions, which are empirically determined. We hypothesize that these fractions might not represent the true magnitude of the Brazilian sugarcane environment and that management practices can further reduce this fraction loaded into the environment. In two field trials, we measure the herbicides and nitrate loaded into the environment through in situ measurements, determine their loss fractions, compare them with some empirical models, calculate the GWF, and estimate the potential for nitrate pollution attenuation with the adoption of split and incorporated nitrogen application. Both hypotheses are confirmed. For nitrate, our results suggest that the leaching runoff fraction used in most GWF studies is overestimated by about two times, impacting the GWF estimation for the Brazilian sugarcane environment. However, the same conclusion was not possible for herbicides due to the low diversity of the analyzed molecules. In addition, the fertilizer management application reduced the nitrate load on the environment, which the GWF did not necessarily detect.

Effects of the Eating Habits of Romanian Residents on the Water Footprint

Water footprint assessment is an analytical tool that helps us understand how activities, actions, and products from human activity influence the scarcity and pollution of water resources. The objectives of the paper are to study the water footprint that is necessary for the production of food for human consumption as an effective way to determine how food habits put pressure on water resources and to identify ways to reduce the stress found on them. To calculate the water footprint of food products consumed by Romanian residents, two types of data were used: information on the average annual net food consumption of each type of food considered during the research and the water footprint per unit of food consumed. In addition, an analysis was carried out based on the structure of the water footprint and the structure of food consumption. In terms of the structure of the water footprint, the contribution rate of the green water footprint is the highest, reaching 83.5%. This is followed by the blue water footprint and the gray water footprint, accounting for 9.04% and 7.46%, respectively. From the perspective of the structure of food consumption, the consumption of cereals, meat, milk, and dairy products contributed the most to the water footprint of residents’ food consumption, reaching 21.8% and 26.6%, respectively, and contributing 24.2% to the total water footprint of food consumption. Our research is useful for water management, improving the efficiency of use in agricultural technologies, and optimizing the structure of food consumption, such as reducing grain and meat consumption.

Water, land and carbon footprints of Chinese dairy in the past and future

Chinese food consumption shifts towards larger milk consumption. Traditional dairy systems depended on China's grasslands, but modern industrial systems using feed from croplands increase rapidly. The question is whether China can fulfill future milk demand using its natural resources and remain within greenhouse gas emission boundaries. To determine this, this study combines three footprint analyses - water footprint (WF), land footprint (LF) and carbon footprint (CF) - estimated via production chain approach. It compares WFs, LFs and CFs of milk, meat, and manure from six dairy systems in three categories: traditional grazing, traditional mixed, and modern industrial systems. It estimates future footprints for five production scenarios for low and high milk demand. Between 2000 and 2020, industrial systems increased, accounting for 79 % of production in 2020, while traditional production decreased. Traditional grazing systems have large green WFs per kg (17.2 m3), negligible blue WFs and large LFs (46 m2 low quality grassland). Traditional mixed systems have large CFs per kg (2.93 kg CO2) due to low efficiency. Modern industrial systems rely partly on irrigated croplands and have small green WFs, but large blue WFs per kg (0.54 m3), grey WFs (0.24 m3) and small LFs (1.80 m2 cropland). The findings indicate that with dominating industrial systems, milk production relies more on irrigation and limited croplands. In a realistic low demand situation, milk consumption stabilizes. However, consumption triples if the Chinese follow nutritional advice, resulting in 4 to 6 times larger WFs, LFs and CFs in 2035 depending on production scenarios. In 2035, population is largest, from 2035 to 2050 footprints decrease again. However, China cannot produce the milk for a high consumption situation limited by grassland and cropland availability. Alternatively, China could import feed or milk. However, it is questionable whether these huge quantities are available on the global market.

Risk-based decision-making systems in water and food security of global drylands

Abstract This study introduces the foundational principles behind the water footprint in water and food security for evaluating the managerial strategies of agricultural water management in arid areas. The role of green, grey, blue and white water footprints in yield production has been critically investigated to analyze the climate and economic risks. Therefore, a nonlinear hydro-economic framework, which integrates soil water content, food production and economics has been used for the semi-arid regions of China. Non-dimensional form of net benefit per drop was formulated to analyze the uncertainty of economic parameters. Root zone moisture was simulated to estimate crop yield, transpiration, evaporation, water required for irrigation and increase water quality. Five plants of potato, onion, tomato, eggplant and carrot were selected due to similarity in the plant growth season and market criteria. The results showed that the average effective rainfall contributed less than 15% to food production. The impact of the risk of economic fluctuations in achieving the expected net profit has been more than water.

Yield, water, and carbon footprint of rainfed rice production under the lens of mid-century climate change: a case study in the eastern coastal agro-climatic zone, Odisha, India.

Water and carbon footprint assessment can be a good indicator of sustainable agricultural production. The present research quantifies the potential impact of near-future (2026-2050) climate change on water footprint (WF) and carbon footprint (CF) of farm-level kharif rice production of three locally grown varieties (Khandagiri, Lalat, and Swarna) in Odisha, India, under the two RCP scenarios of 4.5 and 8.5. The crop yield, water resources utilization, and greenhouse gas (GHG) emissions were estimated using the calibrated and validated DSSAT crop simulation model. The precipitation and temperature estimates from three regional climate models (RCM), namely HadGEM3-RA, RegCM4, and YSU-RSM were downscaled using the quantile mapping method. The results revealed a considerably high increase in the total WF of the Khandagiri, Lalat, and Swarna rice varieties elevating up to 101.9%, 80.7%, and 71.8% respectively during the mid-century for RCP 4.5 scenario, and 67.3%, 66.6%, and 67.2% respectively for RCP 8.5 scenario relative to the baseline WF. Moreover, compared to the green WF, the blue WF was projected to increase significantly (~ 250-450%) in the future time scales. This could be attributed to increasing minimum temperature (~ 1.7°C) and maximum temperature (~ 1.5°C) and reduced precipitation during the rice-growing periods. Rice yield was projected to continually decline in the future period (2050) with respect to the baseline (1980-2015) by 18.8% and 20% under RCP 4.5 and 8.5 scenarios respectively. The maximum CF of Swarna, Lalat, and Khandagiri rice were estimated to be 3.2, 2.8, and 1.3 t CO2eq/t respectively under RCP 4.5 and 2.7, 2.4, and 1.3 t CO2eq/t respectively under RCP 8.5 scenario. Fertilizer application (40%) followed by irrigation-energy use (30%) and farmyard manure incorporation (26%) were the three major contributors to the CF of rice production. Subsequently, management of N-fertilizer dose was identified as the major mitigation hotspot, simultaneously reducing carbon footprint and grey water footprint in the crop production process.

Spatiotemporal evolution of crop grey water footprint and associated water pollution levels in arid regions of western China

Spatiotemporal evolution of crop grey water footprint and associated water pollution levels in arid regions of western China

Adaptability analysis of water pollution and advanced industrial structure in Jiangsu Province, China

The advanced development of industrial structure is the inevitable way to alleviate a regional water quality crisis. However, the adaptability between water pollution and advanced industrial structure (AIS) remains unrevealed. Analyzing the adaptability between the two can provide important enlightenment for regional differentiated policy making. Taking Jiangsu Province as a case study, this study firstly assessed the status of water pollution during the years 2013–2019 through quantitatively analyzing the grey water footprint (GWF) and grey water footprint intensity (GWFI). Secondly, the level of AIS was measured to identify the characteristics and evolution of the industrial structure. Finally, the Tapio decoupling elasticity coefficient was introduced to reflect the adaptability between GWF and AIS, and between GWFI and AIS. The main results showed that: (1) From 2013 to 2019, the GWF in Jiangsu Province showed a fluctuating decline, with an overall decrease of 27%, while the GWFI continuously declined. Agriculture was the largest sector of GWF in Jiangsu Province from 2003 to 2016, and domesticity replaced it as the largest water pollution source from 2017 to 2019. (2) The overall industrial structure of Jiangsu Province achieved a certain degree of advanced development. However, the level of AIS in Jiangsu Province was not significantly improved, and the secondary industry was still in a leading position. (3) In terms of the total amount and intensity, water pollution in Jiangsu Province was well adapted to the AIS. Among them, the strong decoupling adaptation (SDA), ideal adaptation state, was achieved between the GWF and the AIS in 75% of the year, while there has always been SDA between the GWFI and the AIS in Jiangsu Province. Therefore, targeted policies based on industrial optimization should be rationally formulated aimed at achieving effective water pollution control. The findings of adaptability analysis can be applied to regional zoning management and is conducive to promoting sustainable support of the water environment for industrial development.

Variation and internal-external driving forces of grey water footprint efficiency in China's Yellow River Basin.

Grey water footprint (GWF) efficiency is a reflection of both water pollution and the economy. The assessment of GWF and its efficiency is conducive to improving water environment quality and achieving sustainable development. This study introduces a comprehensive approach to assessing and analyzing the GWF efficiency. Based on the measurement of the GWF efficiency, the kernel density estimation and the Dagum Gini coefficient method are introduced to investigate the spatial and temporal variation of the GWF efficiency. The Geodetector method is also innovatively used to investigate the internal and external driving forces of GWF efficiency, not only revealing the effects of individual factors, but also probing the interaction between different drivers. For demonstrating this assessment approach, nine provinces in China's Yellow River Basin from 2005 to 2020 are chosen for the study. The results show that: (1) the GWF efficiency of the basin increases from 23.92 yuan/m3 in 2005 to 164.87 yuan/m3 in 2020, showing a distribution pattern of "low in the western and high in the eastern". Agricultural GWF is the main contributor to the GWF. (2) The temporal variation of the GWF efficiency shows a rising trend, and the kernel density curve has noticeable left trailing and polarization characteristics. The spatial variation of the GWF efficiency fluctuates upwards, accompanied by a rise in the overall Gini coefficient from 0.25 to 0.28. Inter-regional variation of the GWF efficiency is the primary source of spatial variation, with an average contribution of 73.39%. (3) For internal driving forces, economic development is the main driver of the GWF efficiency, and the interaction of any two internal factors enhances the explanatory power. For external driving forces, capital stock reflects the greatest impact. The interaction combinations with the highest q statistics for upstream, midstream and downstream are capital stock and population density, technological innovation and population density, and industrial structure and population density, respectively.

Simulation and Regulation of Sustainable Utilization of Water Resources in China Based on Improved Water Resources Ecological Footprint Model

The original ecological footprint model of water resources was improved here to explore the rational policy of water resources development and utilization. Aiming to address the problems of high complexity, weak applicability, and insufficient systematicness and dynamics of the existing water resources ecological footprint model, the grey water footprint was introduced into the model to quantify the water for decontamination. In the calculation of the water resources ecological footprint index, the rainwater collection project, seawater desalination, and water resources regeneration, unconventional water sources were considered, and when combined with the system dynamics simulation technology, the SD model of water resources sustainable utilization in China was established. We carried out research on the regulation and control of sustainable utilization of water resources in China. The results showed that the development and utilization of water resources in China remained within the ecological carrying capacity as a whole from 2000 to 2017, and the development of water resources still had potential, but the supply and demand of water resources were unbalanced. Given this, from the perspective of throttling, open-source, and pollution control, six control schemes for sustainable utilization of water resources in China were set up, including the continuation of the current situation, green throttling, pollution control, strict planning for water source development, and comprehensive treatment. Among them, the comprehensive coordination plan for 2018-2050 could properly solve the problem of water resources supply and demand under the conditions of meeting the ecological sustainability of water resources and reasonable water resources load and was the best regulation plan to realize the sustainable utilization of water resources in China. At present, the development of water resources in China lags, which does not match the growth rate of social and economic development on water resources consumption. It is necessary to further strengthen the efforts of open-source, water-saving, and pollution control based on the original policies, so as to alleviate the ecological stress of water resources.

Citation Accuracy: A Case Study on Definition of the Grey Water Footprint

Citing sources is an important part of any research paper. A number of studies in the past have dealt with discrepancies or errors in citations. The citation errors range from several percent to tens of percent. Although in most cases, these are minor formal inconsistencies that do not prevent tracing the source used, there are cases where the citations are incorrect or refer to non-existent articles. In this study, an analysis of the citation of the grey water footprint definition was conducted. The water footprint concept was introduced in 2002 as a methodology for the description of quantity aspects linked to water use in the life cycle. The grey water footprint, which represents the quality aspects of water use, was added to the water footprint concept later on. In this study, almost 300 articles that provide a definition of the grey water footprint and are indexed in the Scopus database were reviewed. More than two-thirds of the articles added the definition by citing the source. Only 3.5% of the citing articles contained an incorrect citation that could be considered a significant error. Although this is a low number, these significant errors have been appearing only in recent years. This suggests the possibility that the percentage of errors could gradually increase as the use of grey water footprint expands in practice. In the first period (up to 2017), only the grey water footprint originators are cited. From 2017 onwards, papers not written by the originators of the grey water footprint idea are also cited.

Livestock or crop? Which deserves more investment to reduce greywater footprint emissions and improve water use efficiency?

Livestock or crop? Which deserves more investment to reduce greywater footprint emissions and improve water use efficiency?

Exploring the drivers of quantity- and quality-related water scarcity due to trade for each province in China

Previous studies have explored virtual water flows due to interprovincial trade within China as well as related impacts on both regional quantity- and quality-related water scarcity aspects. However, the driving forces behind changes in these impacts remain unknown, especially the quality-related water scarcity. Exploring these driving forces can provide targeted measures to mitigate the negative impact of trade on these two types of water scarcity issues. In this study, blue and grey water footprints have been calculated under the consideration of interregional trade between provinces within China and those attributed to international exports from 2007 to 2015. This calculation was based on multi-regional input output model (MRIO). Moreover, the drivers of changes in blue and grey water footprints due to trade have been explored through structural decomposition analysis. The results showed that blue and grey water footprint increased and then slightly decreased from 2007 to 2015 in China. At the same time, interregional trade made an increasing contribution to the blue and grey water footprint, and the proportion increased from 28.8% to 35.0% and from 22.4% to 28.6%, respectively, from 2007 to 2015. The roles of importers and exporters regarding the blue and grey water footprint driven by interprovincial trade within China have changed little, and the quantity- and quality-related water scarcity issues of the main exporters have been intensified by interprovincial trade. A reduction in the water footprint intensity yielded the largest contribution to curb the increase in blue and grey water footprint driven by interprovincial trade. Our study showed that an improvement in efficiency of water use from both quantity and quality perspectives is the key to accomplish sustainable water use in China, especially considering the impact of trade on regional quantity- and quality-related water scarcity issues.

Water footprint and virtual water flows from the Global South: Foundations for sustainable agriculture in periods of drought

Freshwater availability has decreased alarmingly worldwide, with agriculture playing a vital role in this trend. The assessment of the agricultural water footprint (WFagricultural) and virtual water flows (VWF) is fundamental not only in local water resources management and protection, but also in our understanding of the synergies between local water consumption and global markets. Thus, the WFagricultural – broken down into its components (blue, green, and gray) – of the leading 21 crops (grouped in fruit, legumes, cereals, and vegetables), grown in four basins with the most significant agricultural activity in central Chile was determined, estimated in two consecutive years 2017–2018. In addition, due to their great importance in exports, VWFs were assessed, establishing connections according to their origins and destinations. The results show that the green and gray water footprints increased significantly in the south-central basins, while blue water consumption increased in the basins of the central zone, reflecting an evident WFagricultural transition in accord with latitude and climate conditions. Furthermore, VWF showed an annual increase of 44 %, in about 116 destinations, with Asia, Europe, and North America being the preferred destinations, with annual variations of VWFblue- gray associated with increases in exports of apples, cherries, grapes, blueberries, and walnuts, market preferences and growing areas. The present study is an initial step toward sustainable agriculture in a commodity exporting country, one that is relevant in the exploitation of virtual water yet faces severe water deficit problems, distribution, and local water policies. Therefore, contributing to encouraging the efficiency and value of water in the process of a new institutional framework.

Water Footprint Calculation, Effluent Characteristics and Pollution Impact Assessment of Leather Industry in Bangladesh

Leather processing industries consume high volumes of water and chemicals and release effluents into the environment that pollute the surface water and may cause harm to human health. Leather processing involves different wet processing stages such as soaking, liming, chrome tanning, rechroming, neutralization, fatliqouring and dyeing. The pollution generated from the leather processing stages varies in volume, nature and concentrations. Qualitative and quantitative assessments of effluents generated from different stages of leather processing can be useful to understand the stagewise and overall water pollution of leather wet processing and to design and plan pollution abatement initiatives. Water footprints (WF) can help in understanding the total water consumption and water pollution caused by the leather sector. The objectives of this research are to assess the characteristics of effluents generated from different stages of leather processing, calculate the water footprint (WF) and analyze the pollution load of the Bangladesh leather sector. To perform experimental analyses, effluent samples were collected from the following leather processing stages: soaking, liming, deliming and bating, pickling and tanning, wet back, rechroming, neutralization, retanning, dyeing and fatliqouring from four leather processing factories. The key pollution indicating parameters, such as pH, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solid (TDS) and total suspended solid (TSS) of the effluent samples were analyzed. The experimental study showed that almost 52% effluents generate from beam house and tan yard operations, and about 48% effluents generate from post tanning operations. Due to the presence of high amounts of salt, insecticides and bactericides, the effluent generated from the soaking stage contains high BOD and TDS. On the other hand, effluent generated from liming contains the highest amounts of BOD, COD, TDS, and TSS. The reduction or segregation of soaking and liming effluents will be effective in improving the environmental performance of the wet processing of leather. To assess the total water footprint of the leather sector, the water footprint of feed crops and raw hides were calculated, along with the water footprint of the leather processing stages. The water footprints of bovine and ovine crust leather were found to be 34,000 m3/ton and 17,300 m3/ton, respectively. The blue water footprint is higher in soaking, liming and finishing. The green water footprint of leather is mainly contributed by feed crops of farming animals. The grey water footprint was found higher in the soaking, liming, fatliqouring and dyeing stages. About 97% of the water footprints of tanneries are contributed by the wet processing stages. The grey water footprint is the most significant part of the total water footprint of the leather sector, which indicates the impact of high water pollution by the leather processing stages. This study can help to understand the overall scenario of water consumption and water pollution caused by the leather sector in Bangladesh. This study can also be useful in designing sustainable leather products by reducing the total water footprint per unit of leather goods. The systematic approach of this study could be useful for other countries in leather processing.

Driving factor analysis of spatial and temporal variations in the gray water footprint of crop production via multiple methods: A case for west China

The gray water footprint (GWF) can quantitatively evaluate the effect of non-point pollution on water quality in the context of water quantity. It is crucial to explore the driving forces behind the GWF to solve water quality problems. This study quantified the unit GWFs of grain crops and oil crops at the municipal scale in six provinces of western China over 2001–2018, then jointly applied the extended STIRPAT model and path analysis methods to analyze the climatic and socioeconomic driving forces of the GWF. Results show that the key driving forces affecting the GWF obtained by the two methods were consistent. Planting structure and population were the main factors increasing the total GWF, while crop yield was the largest factor inhibiting the unit GWF and demonstrates regional differences. However, when the indirect influence of the driving factor through other factors was large, some driving forces obtained by different methods were reversed. For example, the indirect impact of per capita cultivated land area on the total GWF in Inner Mongolia was large, resulting in a significant positive impact in path analysis and a slight negative impact in the STIRPAT model. To draw more comprehensive and referential conclusions, we suggest using multiple methods together to verify the driving forces and account for the regional differences.

Linking agricultural water-food-environment nexus with crop area planning: A fuzzy credibility-based multi-objective linear fractional programming approach

To readily addressed three key issues including fuzzy parametric information, multiple objectives and fractional ratios in planning problems, this study presents a fuzzy credibility-based multi-objective linear fractional programming approach for building the linkage between agricultural water-food-environment nexus and crop area planning. This approach is developed by incorporating fuzzy credibility-constrained programming into multi-objective linear fractional programming within the optimization model. To demonstrate its applicability, the approach is then applied to the Hetao Irrigation District in the northwest China to unite the multiple objective problems in agricultural irrigation with crop area planning. Three ratio optimization problems associated with agricultural, economic and environmental objectives are concurrently considered including maximum economic benefit per unit of irrigation water, maximum crop yield per unit of irrigated area and minimal grey water footprint per unit of crop production. Therefore, this study has the following advantages. (1) Fuzzy parameters existing in the objective and violated constraints can be effectively tackled. (2) The multiple ratio optimization problems can be efficiently solved through a linearization procedure in a straightforward manner, thereby reflecting desired system efficiency and reducing computational difficulties. (3) The mathematical and practical interactions of agricultural water-food-environment nexus can be investigated based on intermediate variables, i.e., irrigated area, irrigation water, crop yield, economic benefits and greywater footprint. (4) Optimal solutions can be flexibly generated to facilitate crop area planning through given aspiration levels of objective goals and credibility levels of constraints. The results indicate that optimal objective values have slight changes with the form of each objective (e.g., maximization or minimization). The results are useful for facilitating insightful interpretation of inter-relationships among sustainable agricultural production, efficient irrigation water use, and favorable agro-ecological conditions.

Water Footprint of Constructed Wetlands – Lutopecny Case Study

Constructed wetlands (CWs) are effective low-cost applications of nature-based solutions to the treatment of wastewater from small municipalities and isolated dwellings. One type of evaluation of CWs is focused on the effectiveness of wastewater treatment. Another type of CWs evaluation is focused on water balance because wetland plants are adapted to growth in conditions of unlimited water availability, which is associated with a high rate of evapotranspiration. In this study, the water footprint (WF) was used for joining these two evaluations. The blue WF describes water loss from CWs. The grey WF is an indicator of the effectiveness of CW in terms of pollution reduction. This is the first study of CWs that compares the importance of blue and grey WF under different climatic conditions during the year. Data from different seasons were used to calculate the WF of the CW in a temperate climate zone. During cold days, the grey WF is several times higher than the blue WF. Another situation occurs on hot summer days when the blue WF is higher than the grey WF. On all assessed days, the grey WF reduction was higher than the blue WF reduction; it means that the CW saves more clean water in the recipient (needed to dilute discharged pollution) than losses by evapotranspiration.