Freshwater Distribution Research Articles

Staining and resin embedding of whole Daphnia magna samples for micro-CT imaging enabling 3D visualization of cells, tissues, and organs.

Micro-CT imaging is a powerful tool for generating high-resolution, isotropic, three-dimensional datasets of whole, centimeter-scale model organisms. At histological resolutions, micro-CT can be used for whole-animal qualitative and quantitative characterization of tissue and organismal structure in health and disease. The small size, global freshwater distribution, wide range of cell size and structures of micron scale, and common use of Daphnia magna in toxicological and environmental studies make it an ideal model for demonstrating the potential power of micro-CT-enabled whole-organism phenotyping. This protocol details the steps involved in D. magna samples preparation for micro-CT, including euthanasia, fixation, staining, and resin embedding. Micro-CT reconstructions of samples imaged using synchrotron micro-CT reveal histological (microanatomic) features of organ systems, tissues, and cells in the context of the entire organism at sub-micron resolution and in 3D. The enabled "3D histology" and 3D renderings can be used for morphometric analyses across cells, tissues, and organ systems.

Interaction regimes of surface water and groundwater in a hyper-arid endorheic watershed on Tibetan Plateau: Insights from multi-proxy data

The interaction between surface water and groundwater is crucial for the management of water resources and the preservation of ecosystems within arid basins, but knowledge on their interaction regimes at the watershed scale remains relatively limited. The present research synthesizes a range of multi-proxy data, including satellite thermal infrared remote sensing, water piezometric level, hydrochemical analyses, and isotopic signatures (2H, 18O and 222Rn), to elucidate the interaction dynamics and patterns between surface water and groundwater within a representative hyper-arid closed basin on Tibetan Plateau. The findings indicate that the water in the basin originates primarily from the glacier/snow melt water and precipitation in the mountainous regions, and would experience multiple but spatially heterogeneous interactions between river and aquifers from the mountain pass to the tail salt lakes after entering the basin. Water interaction in the piedmont alluvial plain is dominated by the pattern of river seepage into aquifers with a water flux of 25.82 m3/s, which drives the development of hierarchical groundwater flow systems in the basin. The interaction pattern converts to groundwater discharge of the local groundwater flow system at the front of alluvial fan plain, which forms the principal spring-fed rivers and the predominant overflow zone in the basin with the groundwater discharge flux of 3.22 m3/s. Most of these discharged groundwaters would infiltrate back into the aquifers in the middle-upper part of the loess plain with the river water leakage flux of 2.89 m3/s. River water and phreatic groundwater present a gradual enrichment of hydrochemcial components and water stable isotopes (2H and 18O) along the flow path due to the intense evaporation in the loess plain. The multiple water interactions between surface water and groundwater lead to the anomalous distribution of fresh water in the middle-lower stream area, which is related to the intermediate groundwater flow system and the local variable groundwater flow system. Water interaction in the lowest salt-marsh plain is in the pattern of regional groundwater flow system discharge into the tail salt lakes under natural condition, but evolves to only discharge into the artificial brine extraction canals rather than the tail salt lakes after decades of brine exploitation. Our findings provide a conceptual and preliminarily quantificational understanding of the interaction regimes between surface water and groundwater in large arid closed basins at the watershed scale.

Summer Hydrography Conditions at Proglacial Fjord Entrances Along East Greenland

AbstractClimate change is causing widespread melting of land and sea ice in the Arctic, leading to an increase in freshwater input to the ocean. This may have an impact on ocean circulation, marine ecosystems, and biodiversity in the region. Our findings provide new insights into the summer hydrography conditions at proglacial fjord entrances along large parts of the east coast of Greenland. As most freshwater exits the Arctic Ocean through Fram Strait this study focuses on understanding the origin of spatial distribution of temperature and freshwater in the coastal waters in East Greenland. We find that Polar Water and the Atlantic Water variants (Eurasian Basin Atlantic Water/Subpolar Mode Water) dominate coastal waters north and south of Denmark Strait, respectively, and that coastal waters are influenced by advected meltwater from the Arctic Ocean, glacier meltwater and local precipitation. Combining hydrographic observations, water isotope data, and water source fraction analysis, we show that glacier meltwaters can be detected at fjord entrances and down to approximately 200 m. Integrated over the upper 200 m of the water column, glacial meltwater account for approximately 9%, precipitation for around 8% and Polar Water (including sea ice melt) for approximately 83% of the freshwater observed along the East Greenland coast. Below 200 m, Atlantic Water variants dominate the entire coastal section. The freshwater along East Greenland stays close to the coast and we could not detect any glacier meltwater at the slope.

Multi-criteria analysis for sustainable and cost-effective development of desalination plants in Chile

In Chile, there is an increasing demand for freshwater supply for human consumption, agriculture, and industrial activities. In this sense, the country is highly threatened by climate change, which is drastically affecting the availability of water resources in the north-central region due to desertification processes. Therefore, seawater reverse osmosis (SWRO) desalination is becoming one of the most feasible alternatives to address current and future challenges regarding water scarcity in the country. This investigation aims to evaluate potential locations for a sustainable and cost-effective installation of desalination projects; the latter, under a multi-criteria and geographic information system (GIS)-model. The model was tested in the highly water scarcity-threatened Valparaiso Region, Chile, as a case study. The model was developed integrating economic and socio-environmental criteria involved in the development and/or construction of desalination projects. The results of the multi-criteria analysis show that the Valparaıso Region presents optimal areas for developing SWRO projects. Both the northern and central areas of the Region show appropriate locations for installing SWRO plants and their freshwater distribution lines, ensuring short- and long-term water supply, especially for agriculture and population consumption. The results obtained in this study could be extrapolated as a tool to assess the desalination projects development in other world regions to make future desalination projects more viable and sustainable for addressing global water demands.

A comprehensive Earth system model (AWI-ESM2.1) with interactive icebergs: effects on surface and deep-ocean characteristics

Abstract. The explicit representation of cryospheric components in Earth system models has become more and more important over the last years. However, there are few advanced coupled Earth system models that employ interactive icebergs, and most iceberg model studies focus on iceberg trajectories or ocean surface conditions. Here, we present multi-centennial simulations with a fully coupled Earth system model including interactive icebergs to assess the effects of heat and freshwater fluxes by iceberg melting on deep-ocean characteristics. The icebergs are modeled as Lagrangian point particles and exchange heat and freshwater fluxes with the ocean. They are seeded in the Southern Ocean, following a realistic present-day size distribution. Total calving fluxes and the locations of discharge are derived from an ice sheet model output which allows for implementation in coupled climate–ice sheet models. The simulations show a cooling of up to 0.2 K of deep-ocean water masses in all ocean basins that propagates from the southern high latitudes northward. We also find enhanced deep-water formation in the continental shelf area of the Ross Sea, a process commonly underestimated by current climate models. The vertical stratification is weakened by enhanced sea ice formation and duration due to the cooling effect of iceberg melting, leading to a 10 % reduction of the buoyancy frequency in the Ross Sea. The deep-water formation in this region is increased by up to 10 %. By assessing the effects of heat and freshwater fluxes individually, we find latent heat flux to be the main driver of these water mass changes. The altered freshwater distribution by freshwater fluxes and synergetic effects play only a minor role. Our results emphasize the importance of realistically representing both heat and freshwater fluxes in the high southern latitudes.

Spatio-temporal distribution of renewable freshwater resources and their availability in Kosovo—an analysis from the Eastern Region

The study aims to analyze the availability of renewable freshwater resources and their spatiotemporal distribution in the Eastern Region of Kosovo (ERK). As a crucible resource for agricultural, industrial, and commercial activities, water scarcity will lead to water shortages. Kosovo is a landlocked country, and ERK is the most important region for industrial activities (coal, mines) and agricultural use (plains). Located in continental climate conditions, surrounded by middle to high-altitude mountains, the region does not have a favorable spatio-temporal distribution of freshwaters. The determination of the water resources is based on the amount of surface runoff, which being divided per capita, gives indications of the water resources of a region (catchment). For our aims, main river discharge and population statistics are used to analyze the spatiotemporal distribution and availability of renewable freshwater in ERK. Falkenmark Freshwater Indicator with 1.483 m³/capita/year shows that ERK lies under water scarcity, and existing water reservoirs offer low security for water withdrawals, and further reservoirs would prevent water scarcity in the region.

Note on volume and distribution of fresh water in the Amazon River plume under low discharge conditions

In this research communication, we report the results of a field survey conducted in a part of the plume of the Amazon River between 0° and 5°N and offshore of the 28 m isobaths in November of 2022, during the low river discharge season. By comparing the observed vertical salinity profiles ‘disturbed’ by continental discharges within the plume with the virtually ‘undisturbed’ ones outside the plume, we estimated the total content of fresh water in the area covered by the measurements as 203 ± 22 km3, which equals to less than 3% of the average annual Amazon River discharge. Furthermore, we argue that the river-borne continental water was not confined to the upper mixed layer and show that about 37%, or 76 km3, of its volume was entrained into the plume-underlying layer between the mixed layer and the salinity maximum. This point is additionally supported by analysis of chromophoric dissolved organic matter (CDOM) fluorescence in water samples, demonstrating significant concentrations of terrigenous CDOM to depths up to 140 m. We also observed that there was a significant direct correlation between the volume of freshwater accumulated in the affected layer and background stratification (expressed as buoyancy frequency) in the unaffected layer below it.

Implications of the Mississippi v. Tennessee Supreme Court Decision for Interstate Groundwater Management.

Groundwater allocation is rapidly becoming a contentious water resource management problem around the world. It is anticipated that the effects of climate change would further aggravate this problem. Conflicts over the distribution of freshwater are expected to increase as stakeholders want to access more groundwater to meet their growing demands. In the United States, water conflicts are settled through a litigation process. Water litigations can be expensive, protracted, and fraught with complex legal and technical difficulties. A landmark groundwater case involving Tennessee (TN) and Mississippi (MS) was recently litigated in the Supreme Court of the United States (SCOTUS). In this case, MS sued TN for stealing their groundwater and SCOTUS unanimously ruled that the water contained in the aquifer that naturally crosses the border between TN and MS is subject to equitable apportionment. This decision has significant ramifications for groundwater management as it established a precedent for resolving future interstate groundwater litigations. Although the Court has previously applied the legal doctrine of equitable apportionment to settle disputes involving surface water use, this is the first instance in which the doctrine has been applied to resolve an interstate groundwater dispute. Therefore, currently, there are little or no guidelines available for equitably distributing groundwater resources between two states. The objective of this article is to examine this historic legal dispute to fully understand the scientific justification for the judicial stances taken by the plaintiff and defendants, and the legal reasoning for the final verdict. We also discuss the challenges this ruling presents for managing interstate groundwater resources.

The oceanic mixed layer changes along with the state transition of the Beaufort Gyre

Recent state transition of the Beaufort Gyre has drawn great interest in the Arctic research community, but how the upper ocean hydrographic structure varies with this transition remains poorly understood. The upper ocean mixed layer plays an important role in climatic and ecological processes. Therefore, we analyze the Ice-Tethered Profiler (ITP) observations over the last two decades (2004–2022) to investigate the long-term trend of the mixed layer in the Arctic Ocean’s Beaufort Gyre (BG) from an observational perspective. Results show that the linear trend of the BG surface mixed layer depth (MLD) before and after 2015 has changed significantly, characterized by the vanishing or even reversal of the significant deepening trend. This transition is most pronounced in winter. The BG winter mixed layer is significantly cooler, saltier and denser in the mid-transition period (2013–2017) compared to the pre-transition period (2004–2012), but becomes significantly warmer, fresher and lighter in the post-transition period (2018–2022). The transition feature of the depth of maximum buoyancy frequency in the upper BG is similar to that of MLD, while this maximum decreases significantly in both the mid- and post-transition period when compared to their previous period. The deepening signal of MLD is propagated eastward, which coincides with the recent transition of BG position and freshwater distribution. Mechanism analysis further reveals that the reversal of winter MLD trend before and after 2015 may be due to changes in surface wind stirring and Ekman pumping. This study extends the investigation of the recent state transition of BG considering the upper hydrographic structure.

Global freshwater distribution of Telonemia protists.

Telonemia are one of the oldest identified marine protists that for most part of their history have been recognized as a distinct incertae sedis lineage. Today, their evolutionary proximity to the SAR supergroup (Stramenopiles, Alveolates, and Rhizaria) is firmly established. However, their ecological distribution and importance as a natural predatory flagellate, especially in freshwater food webs, still remain unclear. To unravel the distribution and diversity of the phylum Telonemia in freshwater habitats, we examined over a thousand freshwater metagenomes from all over the world. In addition, to directly quantify absolute abundances, we analyzed 407 samples from 97 lakes and reservoirs using Catalyzed Reporter Deposition-Fluorescence in situ Hybridization (CARD-FISH). We recovered Telonemia 18S rRNA gene sequences from hundreds of metagenomic samples from a wide variety of habitats, indicating a global distribution of this phylum. However, even after this extensive sampling, our phylogenetic analysis did not reveal any new major clades, suggesting current molecular surveys are near to capturing the full diversity within this group. We observed excellent concordance between CARD-FISH analyses and estimates of abundances from metagenomes. Both approaches suggest that Telonemia are largely absent from shallow lakes and prefer to inhabit the colder hypolimnion of lakes and reservoirs in the Northern Hemisphere, where they frequently bloom, reaching 10%-20% of the total heterotrophic flagellate population, making them important predatory flagellates in the freshwater food web.

Observations of river-wave interactions at a small-scale river mouth

Small coastal rivers often discharge directly into the surfzone, where the fate of freshwater and river-borne materials (e.g., sediment, nutrients and contaminants) is primarily determined by interactions between buoyant plume processes and the nearshore wave forcing. Understanding river-wave interactions in the surfzone is essential to assess coastal water quality and impacts on ecosystem health along adjacent shorelines. These interactions are modulated by the variability in river discharge, offshore wave climate, tidal forcing, and surfzone dynamics, and therefore occur over a wide range of timescales. However, the different timescales at which river-wave interactions occur have not been fully investigated. Here we use in-situ and remote (drone-based) observations collected at the mouth of the Maipo River, a small-scale river system in central Chile, to investigate interactions between the river outflow and the incident wave forcing that may influence the distribution of freshwater along the coast. We focus on interactions occurring at infragravity (wave groups), tidal, and synoptic (offshore wave climate) timescales. The observations included inlet and surfzone deployments, and documented low river discharge conditions (QR∼ 20–27 m3s−1) with variable wave forcing (Hs∼ 1–3 m). We observed that the salinity signal at the river mouth is strongly modulated by the tide, with a freshwater plume forming solely during the ebb. Large oscillations associated to infragravity (IG) motions are continuously observed on top of the tidal variability. These oscillations are evidenced in surfzone salinity, inlet water levels, and inlet velocity during the early ebb when the freshwater plume starts to develop. As the plume evolves into a strong outflow jet during the late ebb, they are not observed in the inlet and become restricted to the surfzone. The combined analysis of drone imagery and in-situ observations suggests that the observed variability in surfzone salinity at IG frequencies is associated with the arrival of wave groups and the propagation of wave fronts in the plume area. In particular, during the late ebb, the large oscillations in surfzone salinity (amplitude of 15–20 psu) are explained by a contraction and expansion of the outflow plume in response to the variability in the onshore wave forcing at the timescale of wave groups. On synoptic timescales (hours to days), the surfzone salinity responded to the intensity of the offshore wave forcing (∼ 20 m depth), with higher waves promoting lower salinity as freshwater is mostly retained near the coast. A wave-river momentum comparison confirms that the wave forcing had the potential to trap freshwater in the surfzone. This study shows that nearshore waves may influence the dynamics of small river plumes and the fate of freshwater (and associated terrestrial materials) on a wide range of timescales, from infragravity (1–5 min) to hours and days.

Freshwater resources around the reclaimed new land on the Eastern Hengsha Shoal in the Changjiang estuary

Reclaiming estuarine tidal flats is practiced to meet the growing demand for land. The reclaimed new land (RNL) on the Eastern Hengsha Shoal in the Changjiang Estuary is for agricultural production in Shanghai. Whether freshwater resources exist around the RNL has become a critical issue \caused by estuarine saltwater intrusion. In this study, the spatiotemporal saltwater intrusion and freshwater distribution around the RNL at different guarantee rates of river discharge using the improved 3D numerical model ECOM-si was investigated. Three water intakes on Hengsha Island and the northern edge of the RNL were set. The results showed that at different guarantee rates of river discharge during the dry season, there is a relatively sufficient suitable water intake time in the upper RNL. Nevertheless, there is a very limited suitable water intake time in the middle and lower RNL as the guarantee rate increases, especially in January and February. During the flood season, three water intakes can ensure sufficient suitable water intake time. The salinity around the RNL significantly increases under the combined effect of 50% and 95% guarantee rates with a 12 m/s northerly wind in February, resulting in a significant threat to the three water intakes. At the 50% guarantee rate, the suitable water intake times in February are 14.86, 9.78 and 3.53 days at three water intakes, respectively. At the 95% guarantee rate, the suitable water intake time in February is only 0.31 days in the upper RNL, and there is no freshwater in the middle and lower RNL. Overall, there is sufficient freshwater in the flood season and limited freshwater in the dry season for agriculture along the northern edge of the RNL.

Oligochaete distribution in alpine freshwaters: not a mere question of altitude

Alpine freshwater biodiversity is at risk of extinction due to climate change and some species could remain undescribed before they go extinct. These species are not yet included in red lists of protection by law, such as annelids in alpine habitats. Within this context, we studied the annelid fauna in 20 sites located between 1223 and 2703 m asl, belonging to different habitat types (kryal, glacio-rhithral, non-glacial streams, springs, littoral lake zone), in three glaciated catchments of the Italian Alps (Noce Bianco, Careser and Conca-Carè Alto; Trentino Province). The aim of this study was to describe the annelid communities of the different habitat types collected with different sampling methods (kick sampling and drift) and investigate the relationships between species richness and abundance with altitude. Between the years 2000 and 2005, we collected 4,765 individuals in 418 samples. One genus of Polychaeta (Aeolosoma) and 36 species of Oligochaeta were identified, distributed in four families: Enchytraeidae (28), Lumbriculidae (4), Naididae (3 and Tubificinae juveniles) and Haplotaxidae (1). Five species were new to Italy: Cernosvitoviella carpatica, Cernosvitoviella cf. crassoductus, Henlea brucei, Henlea glandulifera and Mesenchytraeus sanguineus. As expected, Enchytraeidae prevailed in all sites with the genera Cernosvitoviella and Cognettia the most abundant and frequent. The regression and cluster analyses and the generalized linear mixed models we performed, highlighted that the differences in species richness and abundance among sites are explainable partly by altitude but mainly by habitat type. A clear longitudinal species turnover was evident only in the Noce Bianco and Careser glacier-fed streams, where taxonomic diversity (tested by Seriation analysis) and abundance increased with increasing distance from the glacier front and decreasing altitude. Also expected, the harsh kryal habitat was the poorest in species and individuals, with a dominance of semi-aquatic and terrestrial enchytraeid taxa. Drift was found to be more effective than kick sampling in collecting oligochaetes, especially in glacier-fed streams where the use of the pond net is generally hindered by their high and highly variable discharge. In conclusion, this study provides new data on oligochaete fauna in alpine freshwaters, useful to implement the prevision models for Alpine biodiversity up to date not including annelid fauna.

Lake plastisphere as a new biotope in the Anthropocene: Potential pathogen colonization and distinct microbial functionality

The not-homogenous microplastics (MPs) distribution in freshwaters results in distinct microbial communities. Yet knowledge regarding plastisphere in metabolic pathways and element cycling behaviors remains limited. In this study, we collected MPs from 15 sampling sites in the Taihu Lake in China, and found that MPs were widely distributed in this freshwater lake, and dominantly composed of fibrous polyethylene terephthalate. Based on the metagenomic analysis, we found that MPs were colonized by Bacteroidia, Alpha-Proteobacteria, and Bacilli as a filter, but depleted in Verrucomicrobiae. Potential pathogens of plant eudicots and monocots were significantly enriched in plastisphere. Predicted functional profiles involved in the metabolism of other amino acids, biosynthesis of other secondary metabolites, and glycan biosynthesis and metabolism were overrepresented in plastisphere. Regarding elemental cycling, functional genes related to nitrogen fixation and nitrification showed 39.6% and 67.5% decline in plastisphere, whereas the genes involved in denitrification and nitrate reduction were significantly enriched. For sulfur cycles, the plastisphere exhibited higher sulfate reduction and sulfur oxidation system activities. Additionally, the taxonomic compositions and predicted functions in the plastispheres were mainly driven by the stochastic processes, while the deterministic processes were more important for the planktonic communities. The distinctions in the microbial composition, the predicted functionality, and the underly mechanisms between plastisphere and planktonic communities illustrated the unique ecology of the new anthropogenic-related plastisphere ecosystems.

Management of physical and chemical water quality in Kotchener drain (Kafr El Sheikh, Egypt)

AbstractMinimization of freshwater consumption is very important in the management of water quality in drainage systems. In this paper, a mathematical technique for mass integration in drain systems was proposed. The main objective of this work is to manage the water quality in Kotchener drain (El‐Gharbia main drain) by chasing the physical and chemical parameters at sources and sinks. Kotchener drain is one of the largest drains in the Nile delta which moves from south of Egypt to the Mediterranean Sea in the north direction. Firstly, the data were collected from the studied area for 2 years along the Kotchener drain area. This was achieved by monthly monitoring five parameters of six sources sites and five sinks' sites. The results reveal that the concentration of the sources parameters in catchment area are within the permissible limits, except major constituents of total dissolved solid (TDS), chemical oxygen demand (COD), and biological oxygen demand (BOD). According to the degree of pollutants in the Kotchener drain area, the effective parameters that affected the irrigation along the Nile delta were studied. Secondly, a mathematical model was constructed by input the data of sinks, sources, and discharge point to Mediterranean Sea. Distribution of wastewater and freshwater between sources and sinks were studied according to the limiting mass loads of sources and sinks. Furthermore, the variables were optimized by applying LINGO Software with adding assumptions and constrains. The most effective network with minimal negative environmental impact was obtained. Application of the introduced mathematical approach results in minimizing the freshwater consumption with minimizing the wastewater discharge.

The role of atmospheric rivers in the distribution of heavy precipitation events over North America

Abstract. Atmospheric rivers (ARs) are filaments of extensive water vapor transport in the lower troposphere that play a crucial role in the distribution of freshwater but can also cause natural and economic damage by facilitating heavy precipitation. Here, we investigate the large-scale spatiotemporal synchronization patterns of heavy precipitation events (HPEs) over the western coast and the continental regions of North America (NA), during the period from 1979 to 2018. In particular, we use event synchronization and a complex network approach incorporating varying delays to examine the temporal evolution of spatial patterns of HPEs in the aftermath of land-falling ARs. For that, we employ the SIO-R1 catalog of ARs that landfall on the western coast of NA, ranked in terms of intensity and persistence on an AR-strength scale which varies from level AR1 to AR5, along with daily precipitation estimates from ERA5 with a 0.25∘ spatial resolution. Our analysis reveals a cascade of synchronized HPEs, triggered by ARs of level AR3 or higher. On the first 3 d after an AR makes landfall, HPEs mostly occur and synchronize along the western coast of NA. In the subsequent days, moisture can be transported to central and eastern Canada and cause synchronized but delayed HPEs there. Furthermore, we confirm the robustness of our findings with an additional AR catalog based on a different AR detection method. Finally, analyzing the anomalies of integrated water vapor transport, geopotential height, upper-level meridional wind, and precipitation, we find atmospheric circulation patterns that are consistent with the spatiotemporal evolution of the synchronized HPEs. Revealing the role of ARs in the precipitation patterns over NA will lead to a better understanding of inland HPEs and the effects that changing climate dynamics will have on precipitation occurrence and consequent impacts in the context of a warming atmosphere.

GLOBAL CLIMATIC TRANSFORMATION: IMPLICATIONS FOR PAKISTAN

Global climate change has tremendous economic, environmental and social implications for Pakistan. Recently, there has been increased awareness about inevitability of climate change and the realization that though everyone is affected, yet not equally. The central argument of this paper is that Pakistan is the victim of global climate change and facing consequences of the action it has not committed. We will analyze the global perspective of climate change, how Pakistan is being affected by climate change and what is policy response of Pakistan for adapting and responding. We will apply qualitative approach for our analysis. Developing world is facing challenges of poor governance, resource scarcity and violence, thus suffer greater because of natural disasters. Pakistan is among those countries which have experienced increasing frequency of flooding and droughts, erratic weather and agricultural pattern, loss of biodiversity and decline in freshwater availability. Social theory forms the basis of understanding of climate related threats to developing countries. It gives rise to conceptual framework of societal vulnerability, which can be used to explain why Pakistan is the major victim of global climate change. Pakistan has experienced serious impacts of climate change in various sectors like agriculture, water scarcity, inter provincial conflicts over resources, public heath, floods and other extreme weather events. This calls for rapid climate action and concrete policy for addressing this rapidly deteriorating situation. The country should enhance is disaster management and coping capacity and work on building the resilience of people and institutions. Availability and distribution of fresh water must be guided by laws formed by coordination of central ad provincial government. For efficient administration, interaction, and implementation, it is crucial to combine the relevant ministries under the aegis of provincial and federal disaster response organizations. Keywords: climate change, Pakistan, social theory, floods, food security, water scarcity.

Bibliometric analysis on hybrid renewable energy-driven desalination technologies

Throughout human history, water and energy have played pivotal roles in the expansion and progress of societies. However, the availability of fresh water on Earth is limited, constituting less than 3% of the global water resources. Moreover, the distribution of freshwater across countries is inequitable, with a considerable amount being returned to oceans and underground reservoirs. The escalating effects of global warming further disrupt the natural water cycle, posing a serious threat to numerous countries in the form of drought and famine. To meet the increasing demand for freshwater, desalination technologies have been widely employed worldwide. Nevertheless, most of the existing commercial desalination methods heavily rely on fossil fuels and contribute to significant greenhouse gas emissions, exacerbating the issue of global warming. Consequently, the integration of hybrid renewable energy sources into desalination processes emerges as a promising solution to simultaneously address the freshwater demand and combat global warming. So, utilizing hybrid renewable energy supply to drive various desalination technologies is a very promising solution to meet freshwater demands and help mitigating the global warming problem. Therefore, it is imperative to gain a comprehensive understanding of the latest advancements in hybrid renewable energy-driven desalination technologies to guide future research endeavors in this domain. The primary objective of this study is to perform a bibliometric analysis in order to identify the key sources, authors, countries, research institutions, and topics within the field of hybrid renewable energy-driven desalination technologies. By utilizing the R Bibliometrix library and the biblioshiny application, a dataset comprising 451 publications obtained from the Scopus database was analyzed. The results of the analysis reveal a substantial increase in the annual publication rate within this research field over the past five years. Notably, Iran, the United States, and China have emerged as leading contributors in terms of total publications. However, it is noteworthy that countries in the Middle East and the Mediterranean region, in addition to China and the USA, exhibit prominent involvement in various categories of research within this field.

Retrieving time series of river water extent from global inland water data sets

The accurate monitoring of the surface water storage as an essential component of the global water cycle requires a realistic representation of river networks and channel characteristics. Since such a representation has not been available for many rivers and is becoming less available even for many gauged rivers, crucial questions about the spatio-temporal dynamics of freshwater in river networks cannot be answered properly.The global coverage and fine temporal resolution of satellite imagery provide the opportunity to obtain time series of surface water extent at the global scale for almost all rivers. However, despite recent advances in satellite imaging sensors, water extraction algorithms, and big data processing capabilities, none of the available global water extent data sets can meet the necessary requirements in terms of accuracy and spatio-temporal resolutions. Due to the inherent complexity of monitoring the river surface extent, efforts have been limited to the development of global river extent data sets with a limited number of temporal layers usually obtained from long-term averaged satellite imagery.In this study, we propose a region-based image restoration algorithm to obtain the river surface extent from a pre-existing global inland water data set by incorporating temporal and spatial constraints between pixel labels. We employ our algorithm on the Monthly Water History maps of the Global Surface Water data set (Pekel et al., 2016). We validate the proposed method on 98 river reaches that their average width ranges from approximately 36m to 3400m with in situ discharge measurements in the Mississippi, Amazon, Niger and Po river basins. The obtained river width time series exhibit a strong monotonic relationship with discharge measurements as the Spearman correlation coefficients are predominantly larger than 0.70 (on average 0.74 for Mississippi, 0.84 for Amazon, 0.86 for Niger and 0.77 for Po rivers). Such a performance confirms that the proposed method can facilitate the acquisition of a global dynamic river extent data set, which plays a key role in better understanding the distribution and availability of freshwater across continents.

Quantitative prediction of toxin-producingAphanizomenoncyanobacteria in freshwaters using Sentinel-2 satellite imagery

This study aimed to develop an empirical model to predict the spatial distribution of Aphanizomenon using the Ridiyagama reservoir in Sri Lanka with a dual-model strategy. In December 2020, a bloom was detected with a high density of Aphanizomenon and chlorophyll-a concentration. We generated a set of algorithms using in situ chlorophyll-a data with surface reflectance of Sentinel-2 bands on the same day using linear regression analysis. The in situ chlorophyll-a concentration was better regressed to the reflectance ratio of (1 + R665)/(1-R705) derived from B4 and B5 bands of Sentinel-2 with high reliability (R2 = 0.81, p < 0.001). The second regression model was developed to predict Aphanizomenon cell density using chlorophyll-a as the proxy and the relationship was strong and significant (R2 = 0.75, p<0.001). Coupling the former regression models, an empirical model was derived to predict Aphanizomenon cell density in the same reservoir with high reliability (R2 = 0.71, p<0.001). Furthermore, the predicted and observed spatial distribution of Aphanizomenon was fairly agreed. Our results highlight that the present empirical model has a high capability for an accurate prediction of Aphanizomenon cell density and their spatial distribution in freshwaters, which helps in the management of toxic algal blooms and associated health impacts.