Water-rich Region Research Articles

Spring water resources in the Tatra Mountains

The Tatra Mountains stand out as the wettest and most water-rich region in Poland. Despite this, limited studies addressed this issue, and current knowledge largely relies on data obtained in the mid-20th century, with a substantial lack of current estimates. This study aims to fill this gap by evaluating the contemporary water resources of springs in the Tatra Mountains. The study bases on the most recent hydrological mapping of 1,018 springs. The spring resources were evaluated using parameters such as the number of springs, specific runoff, and crenological index, analysed across different physiographic regions, tectonic units, and altitudinal zones. Our studies showed that the highest number of springs occurs in the Western Tatras (66%) between 1000 and 1400 m a.s.l., especially within the Sub-Tatric unit. Springs with discharges ranging from 0.1–1.0 dm3∙s−1 constitute approximately 70% of all springs but they contribute to only 8.1% of spring water resources. Total spring discharge amounted to 2726 dm3∙s−1 and was higher in the Western Tatras (1982.5 dm3∙s−1 than in the High Tatras (743.5 dm3∙s−1 . The specific runoff amounted to 12.9 dm3∙s−1 m−2 with the highest total runoff at altitudes occupied by the most abundant karst springs (1000–1100 m a.s.l.). The crenological index amounted to 4.8 springs∙km−2 and was higher in the Western Tatras (6.5 springs∙km−2) than in the High Tatras (4.9 springs∙kmup−2) . The analysis revealed that the only five largest karst springs, constituting a mere 0.5% of all springs, account for 65% of spring water resources in the Tatras.

A revised model for calculating virtual scarce water

Accounting for virtual scarce water facilitates and improves the analysis of virtual water, and facilitates comparisons between water use embodied in products from regions with different water resource conditions. However, previous virtual scarce water models were inadequate for the analysis of both water quantity and quality, and only provided a rough estimate. To address this problem, we proposed a modification of this model. In the revised model, we determined the scarcity induced by inadequate water quality by analyzing the availability of suitable quality water for specific sectors (residential, industrial, agricultural, and environmental) rather than focusing on a single sector (usually environmental). Additionally, the revised model evaluated scarcity from water quantity by considering clean water technologies and environmental flow demand. This comprehensive scarcity measure is then incorporated into an input–output model to determine virtual scarce water. We used two typical Chinese river basins (the Hai River and Pearl River basins) with different water endowments to evaluate the model. We found that in the water-scarcity region the virtual scarce water was more strongly affected by water quality and clean water technologies, whereas in the water-rich region it was more strongly affected by the environmental flow demand. These findings underscored the need for more targeted economic and environmental policies for different regions. Water-scarcity regions should prioritize the promotion of clean water technologies and contaminant mitigation techniques, while water-rich regions should pay more attention to ensuring the environmental flow demand.

Characterization of Water Bodies through Hydro-Physical Indices and Anthropogenic Effects in the Eastern Northeast of Brazil

Brazil, despite possessing the largest renewable freshwater reserves in the world (8.65 trillion m3 annually), faces growing challenges in water management due to increasing demand. Agriculture, responsible for 68.4% of water consumption, is one of the main drivers of this demand, especially in the São Francisco River Basin, where irrigation accounts for 81% of total water withdrawals. Water bodies play a crucial role in sustaining ecosystems and supporting life, particularly along the East-West axis of Alagoas, a water-rich region in the ENEB. This study aimed to map and quantify the spatiotemporal variations of water bodies in the ENEB region and assess the impacts of human activities using MODIS satellite data, applying hydrological indices such as NDWI, MNDWI, and AWEI. Between 2003 and 2022, significant variations in the extent of water bodies were observed, with reductions of up to 100 km2 during dry periods and expansions of up to 300 km2 during wet seasons compared to dry periods. AWEI and MNDWI proved to be the most effective indices for detecting water bodies with MODIS data, providing accurate insights into water dynamics. Additionally, the MapBiomas Rios dataset, despite being resampled from a 30 m to a 500 m resolution, offered the most accurate representation of water bodies due to its methodology for data acquisition. Changes in albedo and surface temperature were also detected, highlighting the influence of climate change on the region’s water resources. These findings are crucial for guiding the sustainable management of water resources, not only in Alagoas but also in other regions of Brazil and similar semi-arid areas around the world. The study demonstrates the hydrological variability in the state of Alagoas, indicating the need for adaptive strategies to mitigate the impacts of climate change and anthropogenic pressures, supporting the need for informed decision-making in water resource management at both local and national levels.

Structural and dynamic behaviour of concentrated aqueous solutions of (poly)ethylene glycols: Insight into the impact of hydrophobicity, hydrogen bonding and chain length

Understanding the delicate interplay between hydrophobicity/hydrophilicity, hydrogen bonding ability and solute size in modulating the chemico-physical properties of aqueous solutions with increasing solute concentration is a challenging task. Here, we focus on how bulk properties, such as diffusion and aggregation behaviour, are affected by the different hydration patterns observed for differently concentrated aqueous solutions of (poly)ethylene glycols, and their corresponding methoxyethers, of various lengths. Using a combined experimental and computational approach, we analyse solutions of ethylene glycol (EG), dimethoxyethane (DME), polyethylene glycol with 4 repeating units capped with either hydroxyl (PEG200) or methoxyl (PEG250DME) tails, and polyethylene glycol with 9 repeating units (PEG400). By disentangling the contributions of hydrophobicity, hydrogen bonding ability, and chain length, we observe that for the smaller solutes electristriction and hydrophobic hydration are the main phenomena occurring. Instead, as the solute becomes larger, these effects give way to the non-trivial conformational flexibility that can either favour or disfavour intermolecular interactions which lead to the formation of water-rich regions excluded from the solute.

Environmental Option and Remedy for Resuscitating Dying Lake Chad

Lake Chad, a vital freshwater reservoir in the Sahel region, faces a severe decline attributed to climate change, population growth, and unsustainable water practices. This study proposes a comprehensive transboundary water transfer initiative, sourcing freshwater from the water-rich regions of south-south, south-east, and south-west Nigeria to rejuvenate Lake Chad and its surrounding basins. This initiative employs a robust methodology comprising hydrological assessments of potential water sources, pipeline design, and construction informed by successful international case studies. Environmental impact assessments, stakeholder engagement, water quality management, and phased pilot project implementation ensure a holistic and sustainable approach. Lessons from projects like China's South-North Water Transfer and Australia's Snowy 2.0 provide insights into best practices for environmental stewardship and community involvement. Anticipated outcomes encompass the restoration of Lake Chad's water levels, revitalization of ecosystems, and socio-economic improvements in local communities. The multi-regional approach involving south-south, south-east, and south-west Nigeria seeks to enhance resilience against climate variability while fostering equitable water distribution and regional collaboration. Continuous monitoring, adaptive management, and knowledge sharing with global initiatives are emphasized to ensure the long-term success and sustainability of the project. This study proposes a novel and inclusive approach to address the challenges facing Lake Chad by leveraging freshwater resources from multiple regions in Nigeria. The outlined methodology prioritizes environmental sustainability, community engagement, and draws upon international successes, positioning this initiative as a model for transboundary water management in regions grappling with water scarcity.

Probing water-driven nanostructures in an ionic liquid using small- and wide-angle neutron scattering: 1-Dodecyl-3-methylimidazolium iodide

In this study, phase variations within a hydrophilic ionic liquid (IL)–D2O mixture were observed in using small- and wide-angle neutron scattering (SWANS). The specific IL used was 1-dodecyl-3-methylimidazolium iodide ([C12mim][I]). Owing to the large neutron scattering length density of deuterium, D2O nanostructures appeared to be enhanced in the SWANS profile. Moreover, the complicated phase diagram of [C12mim][I]–D2O was determined using SWANS. Evidently, the water-rich region featured nanoconfined water (a water pocket), a smectic A phase, a columnar hexagonal phase as a lyotropic mesophase, a bicontinuous cubic phase as a double gyroid, and a layered crystal phase. Additionally, a double gyroid structure appeared in the narrow water-concentration region.

Seepage interaction mechanism of crossing tunnels and existing tunnels: Model test and numerical analysis

High-density urban tunnel engineering produces strong spatial seepage and stability interactions of newly built and existing operational tunnels, which is critical to the safety and resilience of transport infrastructure. Previous research mainly focused on the mechanical response of adjacent tunnel construction and the active deformation control of surrounding rock, while little consideration is given to the influence of spatial intersecting tunnels on the seepage field distribution, especially in water-rich regions. This paper investigates the seepage interaction of crossing tunnels and existing tunnels using dedicated seepage tests and corresponding numerical analysis under different hydrodynamic head heights and spatial crossing forms. The schemes are designed based on the Kexuecheng Tunnel in Chongqing City, China, which is a typical small spacing highway tunnel that crosses five existing railway tunnels in complex hydrogeological environment. According to the results, the seepage funnels generated by intersecting tunnels will overlap each other in space, causing significant changes in the seepage field within the impact area. When the newly built tunnel above-crossing the existing tunnels, the water pressure on lining structure of the small interval tunnel can be reduced by 20 ∼ 30 %. While the impact of the existing tunnel on the seepage field of the new tunnel is mainly reflected in its upper part. The construction of new tunnels is equivalent to adding seepage paths to the upper or bottom of an existing tunnel, reducing its water pressure by 10 ∼ 30 %. The spatial overlap effect will significantly reduce the water pressure at the intersection of tunnels, but also exacerbates the asymmetric distribution of water pressure in small spacing tunnel. According to the W-shaped spatial distribution of the seepage field in small spacing tunnels, the predicted seepage influence range may exceed 80 ∼ 100 m. When the newly built tunnel above-crossing or under-crossing the existing railway tunnels, the water inflow of the small interval tunnel and the overlying tunnel can be decreased by 10 ∼ 30 % compared to the situation without crossing. However, the overall groundwater discharge further increases by 53.9 %. The seepage interactions of newly built tunnels and existing tunnels could provide support for both alignment design and construction of newly built tunnel, and service performance improvement of existing tunnels.

Estimation of Ultrasonic Velocity, Density, Internal Pressure, and Thermophysical Parameters of Ionic Liquid Mixtures: Application of Flory's Statistical Theory.

Flory's statistical theory (FST) has been employed to estimate the ultrasonic velocity, density, internal pressure, and several important thermophysical parameters such as the energy of vaporization, the heat of vaporization, cohesive energy density, polarity index, and solubility for eight binary mixtures of ionic liquids and water within the temperature range of 288.15 to 308.15 K. The ionic liquids chosen for this investigation are [BMim][dca], [BMim][TfO], [BMpy][TfO], [BMpyr][dca], [BMpyr][TfO], [EEPy][ESO4], [HMim][dca], and [MPy][MSO4]. The predicted values of ultrasonic velocity and density show good agreement with the data reported in the literature. It endorses the applicability of FST to these binary mixtures. A comparative analysis of the internal pressure values (Pi) determined by using FST and the standard thermodynamic approach is also presented. The results obtained for Pi using both approaches show good agreement. Besides, for the mixtures under study, the correlation between ultrasonic velocity, density, and surface tension has also been examined. The variation of thermophysical parameters with concentration and temperature changes has been utilized to explore the nature and strength of the solute-solvent interactions prevalent in these mixtures. It is pointed out that A-A-type interactions dominate over A-B-type interactions in water-rich regions of the mixtures.

Dielectric Response of Different Alcohols in Water-Rich Binary Mixtures from THz Ellipsometry.

We report a study on the hydrogen bonding mechanisms of three aliphatic alcohols (2-propanol, methanol, and ethanol) and one diol (ethylene glycol) in water solution using a time-domain ellipsometer in the THz region. The dielectric response of the pure liquids is nicely modeled by the generalized Debye-Lorentz equation. For binary mixtures, we analyze the data using a modified effective Debye model, which considers H-bond rupture and reformation dynamics and the motion of the alkyl chains and of the OH groups. We focus on the properties of the water-rich region, finding anomalous behavior in the absorption properties at very low solute molar concentrations. These results, first observed in the THz region, are in line with previous findings from different experiments and can be explained by taking into account the amphiphilic nature of the alcohol molecules.

Mitigating trade-driven water scarcity via water-saving irrigation in China: Different role of surface water and groundwater

Examining virtual water flows in China, we identified a crucial gap in differentiating between groundwater (GW) and surface water (SW). Understanding the unique roles of virtual GW and SW is vital for local sustainable water use. We firstly track virtual GW and SW flows via inter-provincial trade, using a comprehensive inventory that included GW and SW uses in China. Our findings show nearly two-thirds of Chinese provinces face GW or SW scarcity in 2017, with about 34 % of GW and 31 % of SW use driven by interprovincial trade. Water rich regions acted as virtual SW exporters, while water scarce regions served as virtual GW exporters. Targeted irrigation efficiency improvement strategies, considering regional surface and groundwater pressures, could notably reduce interprovincial trade-driven GW and SW use by 12 % and 7 %. It's crucial to manage GW and SW as single resources, recognizing both their physical and virtual distinctions in local water use.

Future projection of water resources based on digitalisation and open data in a water-rich region: a case study of the city of Klagenfurt

ABSTRACT Implementation of different strategies on the demand and supply side to deal with potential water scarcity is based on a comparison of future water demand and availability of water resources based on different scenarios of climate change and population growth. Especially, the Alpine region is characterised by many small and medium water supply systems (WSSs) having neither human resources nor time for advanced planning, requiring simple methods for estimating future development. Therefore, the aim of this work is to provide future projections of water demand, resource availability, and drinking water quality for an Alpine area based on simple approaches with minimal data requirements. As the results of the case study show, linear and polynomial regression with precipitation and temperature data can illustrate the temporal variation of system input and drinking water temperature with sufficient accuracy and is suitable for an estimation of future development. The groundwater modelling, however, requires the consideration of a non-linear term depending on the depth to obtain reasonable results. Due to the usage of open-access data and the easy approaches developed and applied, a good transferability to other case studies is expected which can provide stakeholders a first assessment of the future need for action.

Analysis of water pressure distribution and optimization of waterproof-drainage system for tunnels in water-rich region

Analysis of water pressure distribution and optimization of waterproof-drainage system for tunnels in water-rich region

Energetic analysis and economic viability of active atmospheric water generation technologies

Water scarcity is a growing global and systematic problem in regions with low groundwater availability. Atmospheric water generation (AWG) technologies are an innovative solution to the water shortage problem, as atmospheric water vapor is a readily available resource even in arid regions, with the drawback of high energy consumption. In this paper, the viability of AWG technologies on an energy and economic level is investigated by thermodynamic modeling of three main active AWG systems consisting of cooling condensation, adsorption and absorption processes. A location analysis model is developed to evaluate the performance based on representative weather data of temperature, pressure and relative humidity over a period of one year to account for seasonal shifts and daily variations in climatic conditions. The specific energy consumption kWh/kg, water production trend and total specific cost are calculated for each technology. Water production by seawater desalination at the nearest coastline and transportation to the site by tanker truck, as well as bottled water prices, are used as benchmarks to assess economic viability. The results show that active AWG systems can only be an economically viable alternative if the water consumption site is relatively far from the coast or other water-rich regions and low electricity costs are available (distance >600 km, electricity price <0.10 US$/kWh). Compared to bottled water, all AWG technologies are in a competitive price range. Absorption systems have an energy efficiency advantage over conventional cooling condensation and adsorption systems (cooling condensation: average 0.42 kWh/kg; absorption: average 0.38 kWh/kg; adsorption: average 1.16 kWh/kg), but require a higher degree of process and plant design development. However, because of the high fluctuation in water production, atmospheric water generation technologies should be considered as a complementary supply to conventional water sources.

Geological exploration of coal mine burnt rock and waterlogged area boundary based on transient electromagnetic and high-density electrical resistivity

The water-rich burnt rock may threaten the safe production of coal mines. Identifying the boundaries of burnt rock and the water-rich area is of great practical significance for the ensuring the safety of mining operations. Transient electromagnetic and high-density resistivity methods are commonly employed in geophysical exploration, such as for investigating the presence of groundwater or delineating boundaries of altered rocks. These methods are non-invasive and provide detailed information about subsurface conditions without the need for drilling or excavation. The Jiangjun Gobi No. 1 open-pit coal mine is situated in the Kalamaili fault zone and is characterized by a high groundwater content. In certain mining sites within the study area, the inflow of water reaches tens of thousands of cubic meters per day, which significantly impacts production and presents major risks. To accurately determine the boundaries of burnt rock and water accumulation areas in the Jiangjun Gobi No. 1 open-pit coal mine, this paper uses different geophysical prospecting methods based on the depth of the strata. The middle and deep parts are investigated using the high-resolution transient electromagnetic method, while the shallow parts are examined using the high-accuracy high-density electric method. Through analyzing the electrical characteristics of the study area, it is inferred that the low-resistivity area in the northwest represents a shallow surface water-rich region. This area extends continuously towards the northwest, is not trapped, and is supplied by surface water. The deep low-resistivity zone primarily consists of sandstone and coarse sandstone. It is inferred that the low-resistance area in the southern part of the study area is also a shallow surface water-rich region, extending towards the east and west sides, not trapped, and supplied by surface water. The deep low-resistivity zone mainly comprises a combination of sandstone, coarse sandstone, and burnt rock, with intermittent layers of mudstone and argillaceous sandstone. The boundary line of burnt rock (coal-bearing strata) is located in the south of the study area. The resistivity of burnt rock (coal-bearing strata) is higher than that of the surrounding rocks, and the resistivity of coal seams is slightly higher than that of sandstone with larger porosity. Estimating the boundaries of groundwater and altered rocks serves to prevent geological disasters and provides valuable information for mineral development and ecological protection.

Effect of Freeze–Thaw Cycles on Microstructure and Hydraulic Characteristics of Claystone: A Case Study of Slope Stability from Open-Pit Mines in Wet Regions

The action of freeze–thaw (F–T) cycles of claystone exerts a profound impact on the slope stability of open-pit mines in water-rich regions. Microstructural changes are observed as a crucial factor in determining the hydraulic characteristics and mechanical behaviors of claystone. The present work integrates a micro-X-ray computed tomography (Micro-CT) scanner, equipped with image processing and three-dimensional (3D) reconstruction capabilities, employed to observe the microstructure of claystone under varying numbers of F–T cycles (0, 10, 20, 30, and 50). Furthermore, seepage numerical simulations based on Micro-CT measurements are conducted to evaluate the hydraulic characteristics. Through meticulous microscopic observation and mechanical analysis, the damage mechanism induced by F–T cycles is revealed and the evolutionary characteristics are analyzed. The two-dimensional (2D) images of 3D reconstructed models unveil the gradual initiation propagation and coalescence of an intricate fissuring network in claystone during the F–T cycles. As the number of F–T cycles increases from 0 to 50, the 3D porosity exhibits exponential growth. Additionally, the influence of F–T cycles substantially enhances the connectivity of fissures. The seepage numerical simulations demonstrate that the evolutionary progression of fissures substantially augments the number of flow paths and enhances permeability. The increase in permeability follows an exponential trend, reflecting the distribution and evolution of fissures under F–T cycles. The impact on permeability arises from a combination of micromechanical properties and the microstructure of claystones. The present research tries to elucidate the microscopic evolution of fissures and their corresponding hydraulic properties in water-saturated claystone, offering significant insights for investigating the slope stability of open-pit mines in regions.

Stability analysis of the rock zone between the tunnel face and the fault fracture zone

Abstract Water and mud inrush is one of the main safety accidents that occur during tunnel construction in water-rich karst regions. Often, faulting occurs in front of the tunnel face, creating a conduit for water and inrush disasters can easily occur. Accurately predicting the safety distance between the tunnel face and the fault fracture zone allows for effectively avoiding water and mud inrush disasters during construction. First, an analytical model of the safety distance of water and mud inrush prevention is proposed, in which the rock zone between the tunnel face and the fault fracture zone is considered a thick rectangular plate with simple support on four sides. Subsequently, the proposed model is successfully verified through comparison with two existing models and engineering cases. Finally, the influence of main model parameters on the safety distance is further determined. This study shows that: (i) The safety distance increases with the increase in the cross-sectional height and width, and the burial depth of the tunnel; (ii) The safety distance increases with the increase in the effective gravity of the rock inside the fault fracture zone and the height of the groundwater table, and decreases in the dip angle of the fault; (iii) The safety distance increases with the increase in fault width, and the fault length has little influence on the safety distance.

Time Lag and Cumulative Effects of Extreme Climate on Coastal Vegetation in China

Rapid global changes are altering regional hydrothermal conditions, especially in ecologically vulnerable areas such as coastal regions, subsequently influencing the dynamics of vegetation growth. However, there is limited research investigating the response of vegetation in these regions to extreme climates and the associated time lag-accumulation relationships. This study utilized a combined approach of gradual and abrupt analysis to examine the spatiotemporal patterns of vegetation dynamics in the coastal provinces of China from 2000 to 2019. Additionally, we evaluated the time lag-accumulation response of vegetation to extreme climate events. The results showed that (1) extreme high temperatures and extreme precipitation had increased over the past two decades, with greater warming observed in high latitudes and concentrated precipitation increases in water-rich southern regions; (2) both gradual and abrupt analyses indicate significant vegetation improvement in coastal provinces; (3) significant lag-accumulation relationships were observed between vegetation and extreme climate in the coastal regions of China, and the time-accumulation effects were stronger than the time lag effects. The accumulation time of extreme temperatures was typically less than one month, and the accumulation time of extreme precipitation was 2–3 months. These findings are important for predicting the growth trend of coastal vegetation, understanding environmental changes, and anticipating ecosystem evolution.

Physical and virtual water transfers in China and their implication for water planetary boundary.

China is an extremely water-scarce country with an uneven distribution of regional water resources. We define two absolute sustainability indicators, using the multi-regional input‒output (MRIO) model to outline the contribution of China's physical and virtual water transfers in mitigating the problem of regional water boundary-exceeding. Although the overall use of freshwater resources is within the safe operation space, 55% of province's water resource development transgresses the local water planetary boundary. Physical and virtual water transfers effectively mitigate the stress of water supply to the water planetary boundary in China's water-scarce regions. Among them, the role of virtual water transfers occupies the main part. The cost of using physical water in water-receiving regions and the situation of virtual water flowing from water-scarce regions to developed water-rich regions cannot be ignored, and a small number of provinces are responsible for most of the virtual water net imports and exports. The obtained results are helpful for the redistribution of water planetary boundary transgressing responsibilities among provinces and the formulation of absolute sustainable water resources management policies.

Molecular dynamics simulation, thermodynamic parameters and solute–solvent molecular interactions of cilostazol (form A) dissolution in (ethylene glycol / ethanol + water) mixtures

This research work reports the cilostazol (form A) dissolution in (ethylene glycol / ethanol + water) mixtures. The co-solvency phenomenon only occurs in mixture of ethanol + water, the maximum solubility in mole fraction is 3.034 × 10-3 at the composition of 0.85. It was found that the solvation performance of cilostazol in two mixtures mainly depend on the ability of forming hydrogen bond (H-bond) of the solutions and van der Waals interaction. According to the preferential solvation results, it is conjecturable that cilostazol molecules are preferentially solvated by water in water-rich regions. With the increase of alcohol concentration, the destruction of water molecular ordered structure by alcohol through hydrogen bond, and solute molecules are preferentially solvated by ethanol and EG. Nonetheless, when 0.86 < x1 < 1 in mixture of ethanol + water, solute molecules are preferentially solvated by water again. The calculation of radial distribution function (RDF) between the atoms of H and O for ethanol and the atoms of N and H for solute is to achieve the interaction of the solute and solvents. The correlation fitting was performed for the solubility data through Jouyban Acree model and its derivative models, and the statistical analysis showed that the Apelblat-Jouyban Acree model is more suitable to present the solubility correlation. Meanwhile, the values of apparent molar standard dissolution enthalpy (ΔHsolo) and apparent molar standard dissolution entropy (ΔSsolo) are positive in each solvents, which reveals that the dissolution process of cilostazol form A is endothermic and entropy favorable within the given temperature range.

Effect of Water on Zn Electrodeposition from a Deep Eutectic Solvent

The electrodeposition of Zn films from a deep eutectic solvent (DES) of ZnCl2 and formamide and its mixture with water was studied. From spectroscopic analyses it was observed that water up to 30 v/v% does not change the Zn coordination in the electrolyte after which significant change in the coordination was observed. Electrochemical studies showed that with increase in water concentration in the DES, higher deposition/stripping current was achieved which was related to lowering of viscosity. The Zn deposit morphology changed significantly with water concentration. At low concentrations of water (up to 20 v/v%), porous Zn nanoplates formed whereas the morphology changed to a dense hexagonal structure on increasing the water concentration. X-ray diffraction results confirmed that at low water concentrations (up to 20 v/v%) Zn-Cu alloy formed. Above 20 v/v% water concentration in the DES, Zn peaks evolved with Zn-Cu alloy forming a shoulder. Based on the electrochemical and spectroscopic studies, it appears that 20–30 v/v% water is the critical region wherein significant changes occur from a DES rich region to a water-rich region.