Differences in Wetland Efficiency Affect Future Lake Water Quality

“十三五”时期，长江流域水环境质量改善明显，但湖泊水质和富营养化状况改善滞后. 长江中游作为我国淡水湖泊集中分布区域之一，部分湖泊存在水环境质量恶化和富营养化加重问题. 本文以长江中游区域国家开展监测的洪湖、斧头湖、梁子湖、大通湖、洞庭湖和鄱阳湖这6个典型湖泊为研究对象，科学评价其2016—2020年水质和富营养化时空变化特征及关键驱动因素，探讨其成因及治理对策. 结果表明，“十三五”时期长江中游湖泊水质和富营养化程度存在较大差异，与2016年相比，2020年大通湖水质改善最为明显，梁子湖水质变差，总磷是影响长江中游湖泊水质类别的主要因子; 洪湖富营养程度恶化最为严重，斧头湖次之，TLI(SD)对长江中游湖泊富营养化评价贡献最大. 目前长江中游湖泊呈有机污染加重和叶绿素a浓度升高现象，洪湖、斧头湖和梁子湖主要与氮、磷营养盐浓度升高有关，而大通湖、洞庭湖和鄱阳湖受水文过程、流域纳污量和湖泊管理等非营养盐因素影响较大. 总氮和总磷仍然是影响“十三五”时期长江中游湖泊水质和富营养化的最主要驱动力，且各湖泊总氮和总磷浓度变化均具有较强正相关性，建议开展河湖氮、磷标准衔接工作，提出河湖氮、磷标准限值或考核目标，以完善河湖水环境质量标准和生态健康影响评价技术规范. 同时，建议长江中游湖泊在开展截污控源、内源控制和生态修复的同时，进一步深化流域管理，特别是对洞庭湖、鄱阳湖、梁子湖和斧头湖等跨行政区湖泊，以提高湖泊治理与修复的系统性和整体性.;During the 13th Five-Year Plan period, the water ecological environment quality of the Yangtze River Basin has improved significantly, but the improvement of lake water quality and eutrophication has lagged behind. As one of the concentrated distribution regions of freshwater lakes in China, the middle reaches of the Yangtze River have the problems of deterioration of water quality and aggravation of eutrophication. This article chosed six typical lakes monitored by national agencies, including Lake Honghu, Lake Futou, Lake Liangzi, Lake Datong, Lake Dongting and Lake Poyang, to scientifically evaluate their spatiotemporal changes, key drivers of water quality and eutrophication from 2016 to 2020, and to discuss the degradation causes and governance countermeasures. The results revealed significant spatiotemporal changes in water quality and eutrophication of those lakes. From 2016 to 2020, the water quality of Datong Lake improved mostly, while Lake Liangzi became worse. TP is the main factor affecting the lake water quality and TLI(SD) is most important in the lake eutrophication evaluation. The eutrophication in Lake Honghu is the most serious, followed by Lake Futou. The lakes in the middle reaches of the Yangtze River widely experienced increasing organic pollution and chlorophyll-a concentration. Such degradation in Lake Honghu, Lake Futou and Lake Liangzi is mainly related to the increase of nitrogen and phosphorus nutrients, while Lake Datong, Lake Dongting and Lake Poyang are greatly affected by non-nutrient factors such as hydrological processes, pollution holding capacity and Lake management. TN and TP are still the main drivers on the water quality and eutrophication of these lakes during the 13th Five-Year Plan period, and change synergistically in each lake. We propose to put forward the standard limits or assessment targets of nitrogen and phosphorus in rivers and lakes, to improve their environmental quality standards of rivers and lakes and the technical specifications for ecological health impact assessment. At the same time, it is recommended that the lakes in the middle reaches of the Yangtze River should carry out pollution control, endogenous control and ecological restoration. It is important to strengthen watershed management, especially the lakes across administrative regions such as Lake Dongting, Lake Poyang, Lake Liangzi, and Lake Futou to improve the system and integrity of lake governance and restoration.

The effects of climate change are expected to be very severe in arid regions. The Sonora River Basin, in the northwestern state of Sonora, Mexico, is likely to be severely affected. Some of the anticipated effects include precipitation variability, intense storm events, higher overall temperatures, and less available water. In addition, population in Sonora, specifically the capital city of Hermosillo, is increasing at a 1.5% rate and current populations are near 700,000. With the reduction in water availability and an increase in population, Sonora, Mexico is expected to experience severe water resource issues in the near future. In anticipation of these changes, research is being conducted in an attempt to improve water management in the Sonora River Basin, located in the northwestern part of Sonora. This research involves participatory modeling techniques designed to increase water manager awareness of hydrological models and their use as integrative tools for water resource management. This study was conducted as preliminary research for the participatory modeling grant in order to gather useful information on the population being studied. This thesis presents research from thirty-four in-depth interviews with water managers, citizens, and agricultural producers in Sonora, Mexico. Data was collected on perceptions of water quantity and quality in the basin, thoughts on current water management practices, perceptions of climate change and its management, experience with, knowledge of, and trust in hydrological models as water management tools. Results showed that the majority of interviewees thought there was not enough water to satisfy their daily needs. Most respondents also agreed that the water available was of good quality, but that current management of water resources was ineffective. Nearly all interviewees were aware of climate change and thought it to be anthropogenic. May reported experiencing higher temperatures, precipitation changes, and higher water scarcity and attributed those fluctuations to climate change. 65% of interviewees were at least somewhat familiar with hydrological models, though only 28% had ever used them or their output. Even with model usage results being low, 100% of respondents believed hydrological models to be very useful water management tools. Understanding how water, climate change, and hydrological models are perceived by this population of people is essential to improving their water management practices in the face of climate change.

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Contrasting water quality trends are occurring within and across North America, with waterbodies experiencing increasing phytoplankton blooms, increasing dissolved organic matter, or both, while others are becoming clearer and bluer; dramatically changing water color. To assess the spatial and temporal variability in water color, we quantified trends in satellite-derived dominant wavelength (λ d ) from 1984 to 2020 for 484 reservoirs across the state of Missouri using the LimnoSat-US dataset. Currently, the vast majority of Missouri reservoirs are classified as green and within a range (538–555 nm) that lies closer to the brown color endmember. Nearly one-third of reservoirs ( n = 159) experienced significant temporal shifts in water color, with more ( n = 91) negative (e.g., bluer) than positive ( n = 68) λ d trends. Linear mixed-effect models indicate that periods of extreme wetness and drought are associated with browner and bluer waters, respectively, and boosted regression trees further reveal that waterbody and watershed characteristics are important predictors for water color trends. We also analyzed trends in summer water quality (WQ) parameters from two long-term monitoring programs to evaluate independent and synchronous changes with λ d . We provide analyses showing that particulate inorganic matter and Secchi depth most strongly correlated with λ d , and total nitrogen and total phosphorus concentrations that are not typically associated with satellite-derived data have greater co-variance with λ d than chlorophyll a . Although bluer waters often reflect reductions in inorganic turbidity, our findings show that they can at times coincide with increases in chlorophyll a . We further demonstrate that while λ d trends broadly align with changes in water quality, co-occurring water quality and color trends in Missouri reservoirs at times defy a simplistic canonical interpretation, particularly in eutrophic waterbodies where changes in nutrient concentrations, chlorophyll a and water color can occur independent of each other. Our results help explain some of the previously observed heterogeneous controls on water color and emphasize the importance of integrating water quality data alongside commonly used landscape and morphological features.

Constituents in water control the amount of light reflected from and absorbed by natural water bodies. This interaction is used as a basis for water quality monitoring using remotely sensed data. Recent studies have shown that water color derived from satellite data can be used to investigate water quality changes due to human and climate change impacts. However, how the change in satellite-based water color corresponds with specific water quality variables needs to be better understood. We analyzed timeseries (2013-2022) satellite-derived water color. We compared it with in-situ measured water quality variables (Secchi depth, turbidity, chlorophyll a, and total suspended solids) for lakes in the Midwest and Northeast regions of the USA. One of the focuses of this study, Lake Erie, observed for size, movement, and toxicity of harmful algal blooms (HABs) at multiple stations. Four bands (ultra blue, blue, green, and red) were extracted from harmonized Landsat and Sentinel-2 data to obtain the tristimulus values. These values are mapped on a chromaticity diagram to get the dominant color wavelength and the Forel–Ule Index (FUI). Results showed a strong relationship between in-situ water quality variables (e.g., Secchi depth and turbidity) and satellite-based FUI. Spatially, the relationship between in-situ water quality variables and water color is not consistent, as there is high variability in the concentration of the observed variables between the sampling locations. For example, measurement stations characterized by yellow to brown colors exhibited a strong relationship with TSS. However, generally, peak chl a concentration corresponds with yellowish green color. Typically, stations with blue to green water color are characterized by lower Chl a concentrations. This in-situ validation is used to infer the water quality of water bodies with no available in-situ monitoring. 

In many countries water quality is a major concern for drinking water management authorities. Freshwater is a limited resource and the demand for good-quality water from natural aquatic systems is therefore high. Additional stress arises from anthropogenic emissions of nutrients, chemicals, pathogens, heat and hydrological alterations as well as from the ongoing global climate change. In this thesis the relevant recent past, present and future factors affecting water quality in the perialpine Lake Biel, used as a source for drinking water, was investigated. Through measurements in the field combined with hydrodynamic logical modelling in one and three dimensions, optimal locations for forthcoming lake water intakes was identified. Water quality properties considered were temperature, oxygen, suspended sediment concentration (SSC) and the risk of subaqueous mass movements. The results identified the forthcoming changes expected in Lake Biel due to the upcoming decommission of the Muhleberg Nuclear Power Plant (MNPP) in 2019. This plant currently release 700 MW of heat into the upstream Aare River in the form of cooling water. The removal of this anthropogenic thermal source will decrease future lake temperature by 0.3 °C (volume average). Due to seasonal river discharge patterns, the main impact of the plant closure will occur during winter. Minor effects are expected in summer in the form of moderately weaker lake stratification. Furthermore, the current fate of thermal pollution emitted from MNPP was linked to the hydraulic residence time of Lake Biel. While short-term anthropogenic thermal impacts in Lake Biel can be large, the system is additionally experiencing continuous warming up to 0.1 °C per decade (volume average) by the ongoing climate change. The climate effect on Lake Biel and its primary tributary, the Aare River, was investigated as well as compared to the much larger Lake Geneva and Rhone River. Climate change causes seasonal river discharge shifts resulting in enhanced river warming in summer and diminished warming in winter, while at the same time SSC increases in winter and decreases in summer. Differences in temperature as well as warming rates between rivers and lakes in turn resulted in a discharge and hydraulic residence time-dependent decrease in climate warming of lakes. Furthermore, deep-water renewal in both lakes is predicted to increase in summer and decreases in winter, possibly influencing the replenishment of deep water oxygen. Additionally, sedimentation patterns in Lake Biel were examined and linked to the historical diversion of the Aare River into the lake. The majority of sediment supplied to Lake Biel ( 80 %) came from large SSC events in the Aare. These events resulted in a selective particle settling pattern, which concentrated sedimentation on the shallow shelf area North-East of the Aare delta. Both the large SSC events as well as this selective sedimentation pattern were connected to weather fronts coming in from the Atlantic Ocean. The research performed here opens up for further promising interdisciplinary research between Meteorology, Climatology, Hydrology and Sedimentology. Inland water management would benefit through increased knowledge regarding the propagation of particles and/or anthropogenic heat, from river catchments into downstream lakes and sediments.

Turbidity and water colour are two easily measurable properties used to monitor pollution. Here, we highlight the utility of a low-cost device—3D printed, hand-held Mini Secchi disk (3DMSD) with Forel-Ule (FU) colour scale sticker on its outer casing—in combination with a mobile phone application (‘TurbAqua’) that was provided to laymen for assessing the water quality of a shallow lake region after demolition of four high-rise buildings on the shores of the lake. The demolition of the buildings in January 2020 on the banks of a tropical estuary—Vembanad Lake (a Ramsar site) in southern India—for violation of Indian Coastal Regulation Zone norms created public uproar, owing to the consequences of subsequent air and water pollution. Measurements of Secchi depth and water colour using the 3DMSD along with measurements of other important water quality variables such as temperature, salinity, pH, and dissolved oxygen (DO) using portable instruments were taken for a duration of five weeks after the demolition to assess the changes in water quality. Paired t-test analyses of variations in water quality variables between the second week of demolition and consecutive weeks up to the fifth week showed that there were significant increases in pH, dissolved oxygen, and Secchi depth over time, i.e., the impact of demolition waste on the Vembanad Lake water quality was found to be relatively short-lived, with water clarity, colour, and DO returning to levels typical of that period of year within 4–5 weeks. With increasing duration after demolition, there was a general decrease in the FU colour index to 17 at most stations, but it did not drop to 15 or below, i.e., towards green or blue colour indicating clearer waters, during the sampling period. There was no significant change in salinity from the second week to the fifth week after demolition, suggesting little influence of other factors (e.g., precipitation or changes in tidal currents) on the inferred impact of demolition waste. Comparison with pre-demolition conditions in the previous year (2019) showed that the relative changes in DO, Secchi depth, and pH were very high in 2020, clearly depicting the impact of demolition waste on the water quality of the lake. Match-ups of the turbidity of the water column immediately before and after the demolition using Sentinel 2 data were in good agreement with the in situ data collected. Our study highlights the power of citizen science tools in monitoring lakes and managing water resources and articulates how these activities provide support to Sustainable Development Goal (SDG) targets on Health (Goal 3), Water quality (Goal 6), and Life under the water (Goal 14).

Surface waters are precious natural resources requiring costly time and labor for effective water quality monitoring. New applications of water color analysis by satellite remote sensing are a promising approach to water quality monitoring for scientific, industrial, recreational, and cultural benefit. Water color is an inherent proxy of ecological health and water quality. This research expands previous applications of lake water color analysis and pioneers water color chromaticity analysis for midcontinent lakes in Minnesota, USA. The results of this project are the first accounts of Minnesota’s Sentinel Lake water color, variability of water color by ecoregion, and temporal consistency of water color within major ecoregions. Minnesota state research initiative, Sustaining Lakes In a Changing Environment (SLICE), ordains “Sentinel Lakes” as representative of lake populations within major ecoregions of Minnesota. NASA’s Landsat 8 OLI historical record of surface reflectance in the visible spectrum was used to observe water color from Sentinel Lakes for 10 years from 2013 through 2022. This work quantifies unbiased water color with chromaticity analysis to interpret dominant visible wavelength from tristimulus values of surface reflectance. Visible light surface reflectance samples were taken from the deepest area within each Sentinel Lakes during the late summer, representing peak annual insolation and trophic activity. A decadal analysis of Sentinel Lake water color was documented, proving conceptual possibility and developing a normality of water color for each Sentinel Lake. Using the median dominant visible wavelength as the characterizing metric of Sentinel Lake water color, the most common water color was observed near 575nm in the green-yellow interface, with more red colors in the Northeastern and Southern parts of the state and a noticeable lack of blue colors. Statistical analysis demonstrated water color varies within an ecoregion and specific colors were not unique to any particular ecoregion. Noticeable annual water color variation in the Canadian Shield ecoregion was attributed to forested catchments and undisturbed hydrology. Decadal patterns of water color in a Sentinel Lake operate as instructive bounds for the investment of further resources when a water color anomaly occurs. Land use and climatic factors are important considerations for understanding the controlling factors of water color. Satellite remote sensing of water color offers a unique opportunity for the development of supplemental monitoring of water quality and ecological health of natural resources.

Supported by EU funds, the European research community has been putting much effort into providing model-based tools to support water resource managers in implementing water management as well as the implementation of the Water Framework Directive. This paper presents the results of a two-year long elicitation phase which aimed to explain why the use of tools in water management is not as great as the corresponding investment in applied research in this area might suggest it should be. The paper identifies a gap between water managers and research community that is evidence of a mutual misunderstanding of the fundamental activities of both communities. We elaborate on these misunderstandings between these two communities by focussing on their attitudes towards seven assumptions that derived from an elicitation phase carried out between 2003 and 2004. These misunderstandings appear to revolve around the issues of the role and importance of model-based tools in water management; the transferability of models to new target sites; the role of participatory modelling in water management; how to solve lack of confidence in model-based tools; the development of computer user interfaces to improve tool usability; and the nature of model integration. Based on these insights, recommendations for improving research, development and ultimately the use of model-based tools in river basin management processes are proposed. The recommendations include improving researchers’ understanding of water management processes and the role their tools play within such a process; identifying for both communities the importance that such tools can play as part of social learning-oriented management processes; improving the role of software consultancies as carriers of research results; considering new methods of model transferability between target basins; and expanding the structure of funding for academic research and development projects to allow the greater provision of non-technical requirements such as post-development tool maintenance and transferability, required by water managers.

In water resources management, there exists a significant disconnect between interests and goal stettings of stakeholders, policy-makers, and decision-makers. Researches have shown that water quality indices have become useful tools for water quality assessment and management. This study aims to determine the groundwater quality status of the Vietnamese Mekong Delta with a suitable water quality index regarding the European Water Framework Directive and the Vietnamese National Regulation. Building on existing works, the needed Water Quality Index must have the following fundamental properties: independence of the particular set of quality parameters and sensitivity to individual bad parameters. Based on a review of the literature on water management and theories of water quality indices, the Canadian Water Quality Index (CCME WQI) is chosen as the basis of argumentation, because it has the first of the above properties. Analysis of the implicit statistical data, especially the inclusion of the number of quality parameters with one failed test (Scope) as well as the number of failed tests (Frequency) in the definition of CCME WQI, demonstrated that CCME WQI is also a quality index for the quality of water control: a high number of failed tests or a high number of quality parameters with failed tests indicate that water control is not sufficient. Nevertheless, there are situations where water must be regarded as good, while CCME WQI qualifies it as bad by its statistical factors. Therefore, this research presents a modification of CCME WQI, called Modified Canadian Water Quality Index (MCWQI), which widely has the same behavior as CCME WQI but is better in situations where the statistical factors furnish the wrong picture of the situation. The useability of MCWQI is verified by an application to the case study “Groundwater Quality in Mekong Delta”. The results concerning the Vietnamese groundwater regulation and the European drinking water regulation are compared. MCWQI is defined as a new tool to help not only water stakeholders and policy-makers but also communities to target scant resources more effectively and sustainably.

Increasing water irrigation demand combined with water scarcity and deterioration of the water quality in the Lower Jordan Valley (hereafter referred to as LJV) - Palestine, has led to a serious challenge in managing current and future water demands. This problem is not restricted to Palestine but to the region in general. Providing feasible solution strategies for water management has demonstrated to be a complex task. Mismanagement of water resources aggravates the problem. Therefore, integrated water resources management promises applicable and creative solutions for the future in terms of water strategies. The main goals of this study are to develop these strategies end based on regional agricultural strategies development. The Case Study Area (Hereafter referred to as CSA), Auja area, is located in the LJV., CSA has suffered from water scarcity and water quality deterioration, This was manifested in decreasing irrigated lands from 10,000 donums in 2010 to only about 4,000 donums in 2013and change in crop patterns in the area. Moreover high chloride concentration in shallow aquifer - with 2000μs/cm² in some wells - has caused increased deterioration in water quality. Therefore, the study investigated creative alternatives based on integrated available water resources management and the exploration of non-conventional resources in the area. The study assumed many strategies of agricultural and water resources development, which jointly constitute strategies of firstly, agriculture development and secondly, water strategies. Both strategies should act as the core of the problem as well as its solution. Accordingly, integrated water resources management (hereafter referred to as IWRM) focused on managing aquifer recharge (MAR) and using brackish water in irrigation. This idea is the base for the assumption of this research. MAR and brackish water eventually are top priority scenarios for meeting water requirements in the future. Decision-makers are urged to take these scenarios into consideration to achieve sustainable development plans in the Palestinian territories. Irrigated lands in the CSA cover 3,800 donums vis-à-vis 30,000 irrigable donums. Main water resources come from Auja Springs and shallow aquifer wells. Available irrigation water does not exceed 3.5 Mm3/a. CSA is served by field survey including soil, water, land, and agriculture cover use. CSA is composed of three Agricultural land zones: zone 1, zone 2 and zone 3. These zones reflect the current cultivated area as well as lands expansion scenarios for an additional 8,500 donums of new irrigated lands with plantations of date palm trees, intensive green house agriculture and grapes. The scenario is based on soil profile analysis of root zone and soil hydrochemistry analysis. Water Management Strategies towards Sustainable Agricultural Development XVI These three land zones represent three agricultural development strategies based on water budget analysis and are jointly linked with the three assumed water strategies. The three water strategies (WSs) are: 1- WS I which is the Do-Nothing approach which reflects large water quantities deficit; 2-The WS II is based on MAR scenario, the Mathematical model of transient GMS-Modflow It is considered as a tool for water management in the CSA. It supplies 2 million cubic meters of surplus water by direct injection into the shallow aquifer wells, in addition to infiltrated flood surface run-off from Wadi Auja. 3-The WS III, is based on 100% of IWRM using all non-conventional water resources, varying from brackish water desalination and treated effluent to importing water from outside the CSA and the use of Current Untapped Water Resources (CUWR). This strategy will change the current crop pattern taking into consideration the water budget. It could offer additional 12 million cubic meters (Mm3) for the extra irrigated expanded land scenario. Evaluating the best management scenarios regarding performance and impact assets based on Driving-Pressure-State-Impact-Response (DPSIR) frame work, would give several decision variables (DVs) as a prelude to form decision criteria analysis and analytical hierarchy procedure (AHP) used for scaling and weighing different decision variables (DVs) This would produce the best management scenario by mixing brackish and fresh water and completely change the crop pattern in the CSA. The change would accrue through planting date palms. In this context, MAR scenario comes as intermediate priority by evaluation results, although it would need further investigation in the future.

In recent years, the severe deterioration of water quality and eutrophication in the Yangtze River has brought much trouble to people’s lives. Because of this, numerous management departments have paid more and more attention to the treatment of the water environment. In order to respond to water environmental protection policy and provide management departments with a basis for refining water quality, this paper takes the Zhuzhou section of Yangtze River-Lushui watershed as its research object. First, we used the Water Quality Analysis Simulation Program (WASP) model as a tool, and obtained the pollution load using the FLUX method formula. During the calibration process, the sensitivity analysis method, the orthogonal design method, and the trial and error method were used. Then, we verified the results by using water quality monitoring data published by Zhuzhou Ecological Environment Bureau. Following that, the water environmental capacity of the Lushui River in normal, wet and dry periods was calculated using the WASP model: the chemical oxygen demand (COD) was 14,072.94 tons/yr, 17,147.7 tons/yr and 10,998.18 tons/yr, respectively; ammonia nitrogen (AN) was 469.098 tons/yr, 571.59 tons/yr and 366.606 tons/yr, respectively; and total phosphorus (TP) was 93.8196 tons/yr, 114.318 tons/yr and 73.3212 tons/yr, respectively. The results show that the WASP model is applicable and reliable and can be used as an effective tool for water quality prediction and management in this area.

Earth Observation and DSS Technical Support Tools for Operational Water Management: User's Feedback on MyWater Project

Water quality monitoring of large reservoirs in China based on water color change from 1999 to 2021

Despite widespread enthusiasm for the development and use of the water footprint concept, some concerns have been raised about the concept itself and its usefulness. A variety of methodologies have been developed for determining the water footprint of a country, each of which varies with respect to how individual countries deal with different forms of water use. Following an extensive review of the literature related to water footprints, this thesis focuses on critically examining the concept of the water footprint in the specific conditions and circumstances of Libya, an arid and water-scarce country. In addition, it explores how the water footprint concept can be applied to existing water resource management to meet the increasing water demand to attain food security and attempts a critical evaluation of the water footprint concept as a tool for water management policy makers in Libya. Two philosophical paradigms (positivism and interpretivism) were utilized to gather data related to the water management system in Libya. Data were collected through semi-structured interviews conducted with selected participants, questionnaires distributed to farmers, critical analysis of pertinent official documents, literature review and the researcher`s own non-participant observation. Direct field observation of agricultural practices in selected study areas in Libya was conducted based on the experience of the researcher and was used to augment the data collected by other methods and to gain an in-depth understanding of the effectiveness of current water policies. The water footprint was calculated according to national statistical information. As the agricultural sector is responsible for more than 85% of the total water use in the study area, Libya, this study focuses on agricultural water use. This research has identified a number of key issues in relation to current water and agriculture management practices and the potential use of the water footprint as a tool to develop water management. Although the current water management seems to be theoretically well drafted, it is not implemented and water polices require review, revision and reformulation. The national water footprint of Libya has been estimated and analysed for the period of 2001–2009. The internal water footprint (internal water use) in the agricultural sector was between 1.9-2.5 Gm3/year (a total of 19 G m3 over the study period), while the external water footprint (imported products) was between 6-12G m3/year of water in virtual form. As the internal water footprint represents only water used to produce products consumed by a country’s inhabitants and excludes water for exports, in countries which have negligible exports, such as Libya, the water footprint concept would not add value for water resource management because, in that case, internal water footprint would be as same as actual water withdrawal. Despite the potential value of the water footprint concept as a tool for water management, the authorities of a region or a country already know the amount of water consumed and required to be withdrawn from domestic water resources. Thus, this knowledge is already available to the decision-makers and little new information is contributed by the water footprint concept. Furthermore, the concept considers only the volume of water consumed and there is no mention of other inputs of crop production, such as the water used in the production of fertiliser and pesticides, nor does it take into account opportunity costs.