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Vietnam Mekong Delta (VMD), the country’s most important food basket, is constantly threatened by drought-infused salinity intrusion (SI). The SI disaster of 2020 is recognized as the worst in recent decades, hence inspiring this perspective article. The authors’ viewpoints on the disaster’s impacts and causes are presented. The arguments presented are mainly drawn from (i) up-to-date publications that report on the recent SI intensification in the VMD and (ii) the power spectral analysis results using water level data. We verified the intensifying SI in the VMD both in its frequency and magnitude and remarked on four of the key SI drivers: (i) upstream hydropower dams, (ii) land subsidence, (iii) the relative sea-level rise, and (iv) riverbed sand mining. Also, a non-exhaustive yet list of recommendable management implications to mitigate the negative effects of the SI is contributed. The mitigation measures must be realized at multiple scales, ranging from pursuing transboundary water diplomacy efforts to managing internal pressures via developing early warnings, restricting illegal sand mining activities, alleviating pressures on groundwater resources, and diversifying agriculture.

Irrigation with saline groundwater has become necessary to overcome freshwater scarcity in the agricultural industry in arid areas. However, the effects of long-term saline groundwater irrigation on soil salinity and bacterial diversity have rarely been examined. In this study, a Lycium ruthenicum field was divided into two parts and subjected to flooding irrigation with saline groundwater (pH 7.81, total salinity 0.95 g L −1 ) and surface water (pH 7.76, total salinity 0.36 g L −1 ) for 8 years. After 8 years of irrigation, the soil salinity and salt ion content (i.e., Na + , Mg 2+ , K + , Ca 2+ , Cl − and CO 3 2− ) in the groundwater irrigation group were significantly greater than those in the surface water irrigation group ( p  < 0.001), with notable accumulation in the topsoil (0–5 cm) ( p  < 0.01). The bacterial community structure differed between the surface water and groundwater irrigation groups. Salt-tolerant bacterial groups (e.g., Balneolaceae and Halomonadaceae) and species (e.g., the marine bacterium JK1007, the bacterium YC-LK-LKJ35, and Methylohalomonas lacus ) dominated in the groundwater irrigation environment. Additionally, bacterial communities were associated primarily with soil salt ions (RV = 0.66, p  < 0.001). The characteristic bacterial taxa in long-term groundwater irrigation soils were salt-tolerant species (e.g., the marine bacterium JK1007, the bacterium YC-LK-LKJ35, and Methylohalomonas lacus). These findings suggest that salinity is the key factor driving differences in bacterial community structure between long-term groundwater and surface water irrigation. The long-term use of surface water and groundwater for irrigation has different impacts on soil environments, with groundwater irrigation having a more pronounced negative effect. Highlights. The long-term effects of this practice on soil salt accumulation and bacterial diversity were examined. This study provides potential applications for sustainable land management in similar ecological contexts. Groundwater irrigation is characterized by saline-tolerant keystone species. Salinity filtering was used to determine the pattern of bacterial community construction. Highlights The long-term effects of this practice on soil salt accumulation and bacterial diversity were examined. This study provides potential applications for sustainable land management in similar ecological contexts. Groundwater irrigation is characterized by saline-tolerant keystone species. Salinity filtering was used to determine the pattern of bacterial community construction.

Soil salinization and waterlogging are critical environmental issues affecting agricultural productivity and cultural heritage preservation, particularly in arid regions. This study investigated soil degradation processes in the archaeologically and agriculturally significant northeastern Nile Delta of Egypt. The objective was to assess the severity of soil degradation and identify key drivers related to water resources and soil characteristics to aid in the development of management strategies. The research employed a multi-faceted approach, including hydrochemical analyses (of groundwater, irrigation water, and soil), water quality indices calculations, statistical analyses, and satellite data. The results revealed high levels of soil salinization in the northern and central areas, with 64% of soil samples classified as strongly and very strongly saline. Soil chemistry indicated salinization sources linked to sodium chloride dominance. Satellite data from Sentinel-2 images and SRTM digital elevation data showed widespread severe waterlogging in the northern lowlands. The Irrigation Water Quality Index (IWQI) values indicated that 87.5% of irrigation water samples posed severe restrictions due to high salinity and sodium hazards, which were mismatched with the low soil permeability observed in 81% of the collected samples exhibiting clay texture and covering most of the study area. Furthermore, shallow groundwater at depths of 0.5–3 m with high salinity was detected, where total dissolved solids exceeded 20,000 mg/L, and Na-Cl water types prevailed, indicating saltwater intrusion. A strong positive correlation ( r  > 0.83) was found between shallow saline groundwater and soil salinity. The combination of poor irrigation water quality, shallow saline groundwater tables, and low-permeability soils created a synergistic effect that severely compromised soil health and agricultural productivity. It also posed severe risks to the structural integrity of archaeological sites and buried artifacts through accelerated physical and chemical weathering processes. This necessitates an urgent mitigation strategy to combat soil degradation in this critical area.

INTRODUCTION TO DESALINATION Explore the principles, methods, and applications of modern desalination processes Introduction to Desalination: Principles, Processes, and Calculations delivers a comprehensive and robust exploration of desalination highlighted with numerous illustrative examples and calculations. The book is divided into three sections, the first of which offers an introduction to the topic that includes chapters covering global water scarcity and the need for \"new water.\" The second section discusses the desalination process, including evaporation, reverse osmosis, crystallization, hybrid systems, and other potable water processes. The final part covers topics that include water conservation, environmental considerations of desalination, economic impacts of desalination, optimization, ethics, and the future of desalination. The book also includes: A comprehensive introduction to desalination, including discussions of engineering principles, the physical, chemical, and biological properties of water, and water chemistry An extensive engineering analysis of the various desalination processes Practical discussions of miscellaneous desalination topics, including the environmental and economic effects of the technology Perfect for process, chemical, mechanical, environmental, and civil engineers, Introduction to Desalination: Principles, Processes, and Calculations is also a valuable resource for materials scientists, operators, and technicians working in the field.

Pretreatment of raw feed water is an essential step for proper functioning of a reverse osmosis (RO) desalination plant as it minimizes the risk of membrane fouling. Conventional pretreatment methods have drawbacks, such as the potential of biofouling, chemical consumption, and carryover. Non-conventional membrane-based pretreatment technologies have emerged as promising alternatives. The present review focuses on recent advances in MF, UF, and NF membrane pretreatment techniques that have been shown to be effective in preventing fouling as well as having low energy consumption. This review also highlights the advantages and disadvantages of polymeric and ceramic membranes. Hybrid technologies, which combine the benefits of conventional and non-conventional methods or different membranes, are also discussed as a potential solution for effective pretreatment. The literature that has been analyzed reveals the challenges associated with RO pretreatment, including the high cost of conventional pretreatment systems, the difficulty of controlling biofouling, and the production of large volumes of wastewater. To address these challenges, sustainable hybrid strategies for ceramic membrane-based systems in RO pretreatment are proposed. These strategies include a thorough assessment of the source water, removal of a wide range of impurities, and a combination of methods such as adsorption and carbon dioxide with a low amount of antiscalants. Furthermore, the suggestion of incorporating renewable energy sources such as solar or wind power can help reduce the environmental impact of the system. A pilot study is also recommended to overcome the difficulties in scaling ceramic systems from laboratory to industrial scale. The review also emphasizes the importance of conducting an effective assessment to suggest a treatment for the brine if needed before being discharged to the environment. By following this framework, sustainable, energy-efficient, and effective solutions can be recommended for pretreatment in desalination systems, which can have significant implications for water scarcity and environmental sustainability.

Saltwater intrusion is the leading edge of sea-level rise, preceding tidal inundation, but leaving its salty signature far inland. With climate change, saltwater is shifting landward into regions that previously have not experienced or adapted to salinity, leading to novel transitions in biogeochemistry, ecology, and human land uses. We explore these changes and their implications for climate adaptation in coastal ecosystems. Biogeochemical changes, including increases in ionic strength, sulfidation, and alkalinization, have cascading ecological consequences such as upland forest retreat, conversion of freshwater wetlands, nutrient mobilization, and declines in agricultural productivity. We explore the trade-offs among land management decisions in response to these changes and how public policy should shape socioecological transitions in the coastal zone. Understanding transitions resulting from saltwater intrusion—and how to manage them—is vital for promoting coastal resilience.

The Mekong delta is Vietnam’s premier rice growing region, forming the livelihood basis for millions of farmers. At the same time, the region is facing various challenges, ranging from extreme weather events, saline water intrusion, and other anthropogenic pressures. This study examines how saline water intrusion and drought have affected rice yield in the Vietnamese Mekong Delta (VMD). Applying the Standardized Precipitation Index (SPI) and the maximum and minimum values of annual average salinity, we spatially examine the effects of drought and saline water intrusion on rice yields over a 40-year period (1980–2019). Our results highlight that 42% of the natural land area of the VMD has experienced increased drought occurrence during the winter-spring (WS) rice cropping season, while certain inland regions have additionally experienced increased drought occurrence during the summer-autumn (SA) rice cropping season. The Tri Ton Station, which has a significant Sen’s slope of −0.025 and a p-value of 0.05, represents an upstream semi-mountainous part of the delta, indicative of a rising severity of reoccurring drought. It should be noted that the yield decreases during the summer-autumn season as the positive SPI_SA increases. Salinity, on the other hand, is associated with SPI_WS during the winter-spring season. Our results highlight the need for improved evidence-based planning and investments in priority adaptation for both sustainable water infrastructure and to improve system resilience.

Projected sea-level rise will raise coastal water tables, resulting in groundwater hazards that threaten shallow infrastructure and coastal ecosystem resilience. Here we model a range of sea-level rise scenarios to assess the responses of water tables across the diverse topography and climates of the California coast. With 1 m of sea-level rise, areas flooded from below are predicted to expand ~50–130 m inland, and low-lying coastal communities such as those around San Francisco Bay are most at risk. Coastal topography is a controlling factor; long-term rising water tables will intercept low-elevation drainage features, allowing for groundwater discharge that damps the extent of shoaling in ~70% (68.9–82.2%) of California’s coastal water tables. Ignoring these topography-limited responses increases flooded-area forecasts by ~20% and substantially underestimates saltwater intrusion. All scenarios estimate that areas with shallow coastal water tables will shrink as they are inundated by overland flooding or are topographically limited from rising inland.Sea-level rise raises water tables, causing flooding from below and saltwater intrusion. A modelling study predicts that coastal California groundwater flooding will expand 50–130 m inland with 1 m of sea-level rise, with areal flooding extent strongly dependent on topography and drainage capacity.

Solar‐driven interfacial evaporation (SDIE) has attracted great attention by offering a zero‐carbon‐emission solution for clean water production. The manipulation of the surface structure of the evaporator markedly promotes the enhancement of light capture and the improvement of evaporation performance. Herein, inspired by seedless lotus pod, a flexible pristine polypyrrole (PPy) membrane with macro/micro‐bubble and nanotube asymmetric structure is fabricated through template‐assisted interfacial polymerization. The macro‐ and micro‐hierarchical structure of the open bubbles enable multiple reflections inner and among the bubble cavities for enhanced light trapping and omnidirectional photothermal conversion. In addition, the multilevel structure (macro/micro/nano) of the asymmetric PPy (PPy‐A) membrane induces water evaporation in the form of clusters, leading to a reduction of water evaporation enthalpy. The PPy‐A membranes achieve a full‐spectrum light absorption of 96.3% and high evaporation rate of 2.03 kg m−2 h−1 under 1 sun. Long‐term stable desalination is also verified with PPy‐A membranes by applying one‐way water channel. This study demonstrates the feasibility of pristine PPy membranes in SDIE applications, providing guidelines for modulation of the evaporator topologies toward high‐efficient solar evaporation. A seedless lotus‐pod‐inspired asymmetric pristine PPy (PPy‐A) membrane is fabricated via template‐assisted interfacial polymerization for solar‐driven interfacial evaporation. The hierarchical macro/micro open bubbles enhance light absorption of PPy‐A membrane, facilitating omnidirectional photothermal conversion. The unique multilevel structure of PPy‐A membrane induces water evaporation in cluster form, leading to low evaporation enthalpy, achieving highly efficient solar evaporation.

Coastal aquifers are commonly layered, and thus, a clear understanding of groundwater flow and salt transport in layered coastal aquifers is important for managing fresh groundwater. However, the influence of leakage between adjacent aquifers on flow and transport processes remains largely unknown where the influence of tides is considered. This study used laboratory experiments and numerical simulation to examine the processes of flow and transport within a tidal aquifer‐aquitard system (i.e., an unconfined aquifer underlain by a semi‐confined aquifer, with an intervening thin aquitard). The laboratory‐scale observations of the current study are the first observations of offshore fresh groundwater within a semi‐confined coastal aquifer. The numerical and laboratory results are in close agreement, revealing that upward leakage from the semi‐confined aquifer into the saltwater wedge of the overlying unconfined aquifer caused buoyant instabilities to form. The development of freshwater fingers created complex saltwater‐freshwater mixing, leading to mixed saltwater influx‐efflux patterns across the sloping aquifer‐ocean interface. Compared with non‐tidal conditions, tidal forces reduced the net upward leakage from the semi‐confined aquifer to the overlying unconfined aquifer. This increased the horizontal flow toward the sea, which in turn reduced the extent of the saltwater wedge in the semi‐confined aquifer. The higher rates of both fresh and saline submarine groundwater discharge (SGD), caused by tides, led to lower groundwater ages in the semi‐confined aquifer. These findings have important implications for unveiling the complex characteristics of seawater intrusion, SGD and geochemical hotspots within layered coastal aquifers. Plain Language Summary Coastal aquifers contain complex and dynamic hydrological and geochemical processes, which profoundly influence the global water cycle and chemical mass balance. Many coastal aquifers exhibit layerd structures in the form of high‐permeability aquifers alternating with thin aquitards. Inter‐aquifer leakage is a common issue in layered coastal aquifers, but few studies explore its impact on the mixing zone of saltwater wedges. The effects of tides on groundwater dynamics and the seawater extent in layered aquifers also remain poorly known. This study used laboratory experiments and numerical modeling to explore the effects of inter‐aquifer leakage and tides on flow and salinity dynamics within layered aquifer systems. We found that the upward leakage extended the mixing zones from the edges of the saltwater wedge to its interior within unconfined aquifers, leading to mixed saltwater influx‐efflux patterns across the aquifer‐ocean interface. The introduction of tides restricted the seawater extent in semi‐confined aquifers. This is a primary consequence of the tide‐induced increase in the horizontal freshwater flow toward the sea through the semi‐confined aquifer, in addition to the increases in the density‐driven seawater recirculation caused by tides. These findings highlight the important role of inter‐aquifer leakage and tides in layered coastal aquifers. Key Points Leakage from semi‐confined aquifers caused mixed‐convective flow within the saltwater wedge of overlying unconfined aquifers Tidal fluctuations reduced the net upward freshwater leakage, and consequently the extent of seawater, in semi‐confined coastal aquifers Tides increased both fresh and saline submarine groundwater discharge in semi‐confined aquifers, reducing groundwater ages