Deep Water Bodies Research Articles

Evaluation of Deep Learning-Based Water Bodies and Flooded Area Detection with Nanosatellites: The PlanetScope Satellite Imageries and HRNet Model

Evaluation of Deep Learning-Based Water Bodies and Flooded Area Detection with Nanosatellites: The PlanetScope Satellite Imageries and HRNet Model

Hourly to weekly variations in halite precipitation from the hypersaline Dead Sea: The role of evaporation, water cooling and freshwater plume stability

ABSTRACTThick‐bedded halite sequences in the geological record are characterized by lateral variations, reflecting spatiotemporal variations in environmental forcing. Although temporal variations have been examined over seasonal scales or longer durations, there is a paucity of information regarding the dynamics of halite deposition at shorter durations of days and hours. Additionally, the influence of water discharges and surface salinity gradients remains poorly understood. Here, for the first time, in situ, hourly to weekly halite accumulation rates were measured on the Dead Sea floor (ca 20 m water depth), the only modern deep and hypersaline water body. Novel underwater photography methods were developed to directly observe halite precipitation at the lake floor, coeval with monitoring of the environmental drives, i.e. evaporation, meteorological and limnological conditions. Two fundamental environments were explored: a diluted plume environment arising from spring discharge; and a mixed hypersaline environment. The focus was on deposition during winter when the halite accumulation rate is highest, and the relationship between evaporation and halite accumulation is most straightforward since the water column is vertically uniform. Significant spatial variations in halite accumulation were found between the two environments, along with hourly variations in each environment. In the mixed hypersaline environment, over intra‐diurnal timescales, evaporation plays a more significant role in halite precipitation, whereas temperature has a greater impact on seasonal changes. In the diluted plume environment, the stability of the buoyant plume controls the rate of halite deposition; during windstorms, the plume is stirred, with higher surface water salinity and higher rate of halite accumulation. However, under calm winds, the plume is stable, with diluted surface water, and the rate of halite accumulation is a few times lower. Following these new findings, the implications for the interpretation of halite deposits are discussed.

On the importance of mooring cable dynamics in response analysis of submerged floating tunnel using quasi-static and fully coupled dynamic models

Submerged floating tunnels are considered an economical alternative to those conventional bridges in crossing deep and long-span water bodies. The development of accurate modeling methods and simulation tools is the primary requirement for the safe design of submerged floating tunnels. Mooring cables are the primary source of stability of submerged floating tunnels against hydrodynamic loadings, and are commonly modelled using the computationally efficient quasi-static catenary approach. The dynamics of mooring cables can be of significant importance in dynamic responses of the submerged floating tunnel. Therefore, in this study, a discrete catenary element is presented with the aim of its implementation in the fully coupled dynamic analysis of submerged floating tunnels. To study the effect of mooring cable dynamics, the prototype of Qiandao Lake submerged floating tunnel has been used in a comparative study between quasi-static and fully coupled dynamic models. The numerical examples show differences in displacements and cable tensions due to the mooring cable dynamics. Furthermore, the mooring cables dynamics have significant effect on the tunnel shear forces and bending moments. The quasi-static coupled modeling significantly underestimates the tunnel internal forces.

Dissolved organic matter (DOM) is independently stratified in thermally stratified water bodies

Thermal stratification often occurs in deep-water bodies, including oceans, lakes, and reservoirs. Dissolved organic matter (DOM) plays a critical role in regulating the dynamics of aquatic food webs and water quality in aquatic ecosystems. In the past, thermal stratification boundaries have been sometimes used exclusively to analyze the vertical distribution of DOM in thermally stratified water bodies. However, the validity of this practice has been challenged. Currently, there is limited understanding of the formation mechanism and stratification of the vertical distribution of DOM in thermally stratified water bodies, which hinders the analysis of the interactions between DOM and vertical aquatic ecological factors.To address this gap, we conducted a comprehensive study to extensively collect the vertical distribution of DOM in thermally stratified water bodies and identify the primary factors influencing this distribution. We found that DOM was independently stratified in thermally stratified water bodies (including two cases in unstratified water bodies), and that the formation mechanisms and statuses of DOM stratification were different from those of thermal stratification. The boundaries and numbers of DOM stratification were generally inconsistent with those of thermal stratification. Therefore, it is more accurate to divide DOM into different layers according to its own vertical profile, and analyze DOM characteristics of each layer based on its own stratification instead of thermal stratification. This study sheds light on the relationship between DOM and thermal stratification and provides a novel approach for analyzing DOM vertical distribution characteristics and their impact on aquatic ecosystems. This finding also holds significant implications for the design and implementation of environmental management programs aimed at preserving the health and functionality of aquatic ecosystems.

Land Cover Change Detection Using Geo-Spatial Technologies: A Spatio-Temporal Study on Muthurajawela Marsh-Negombo Lagoon Wetland Complex


 Biodiversity conservation and management encompass protecting Earth’s life diversity including species and ecosystems. Conservation efforts involve protecting endangered species and maintaining healthy ecosystems. Muthurajawela Wetland is one of the listed Ramsar sites of Sri Lanka which contains a rich biodiversity and productive ecosystem. Currently, this valuable landscape undergoes a radical change of its form over decades. Therefore, this study aimed to examine land cover changes in this wetland complex over three decades using satellite imagery. For in-depth change detection analysis, both pre-classification and post-classification land cover/use methods were used to assess changes from 1997 to 2023. The study of the Muthurajawela marsh- Negombo lagoon wetland complex used per-classification methods like Normalized Difference Vegetation/Water Indices (NDVI/NDWI) to identify vegetation and water bodies. The Maximum Likelihood Supervised Classification (MLSC) technique categorized the land cover into classes, water, marshland, settlements, vegetation, and barren land. To ensure accuracy, statistical methods such as Confusion Matrix was applied for each land cover class. Furthermore, a detailed post- classification analysis was conducted through Thematic Change Detection, which compared historical changes in land classes to their current status. Thematic Change analysis helped to assess and visualize the changes in each land class over time in relation to the present conditions on the ground. Change detection analysis illustrated that, about 46% land cover of total study has been converted from one land class to another over 3 decades. In 1997, highland vegetation of agriculture, forests, and marshy areas covered 41% of total land while Built-up areas comprised 18% of the land, with agriculture being more prevalent than construction. By 2023, there have been significant changes. Built-up areas make up 38% of the land due to the development of settlements, construction activities and the Katunayake highway project. The study shows a decrease in vegetation and marshland to 6%, possibly due to deforestation. In 2023, bare lands increased due to land reclamation and garbage dumping in the wetland complex. 90% of deep-water areas converted into shallow water. 28.35 km2 of deep-water bodies degraded. Prawn farming also contributed to mangrove destruction in the Negombo lagoon. The study emphasizes the need for sustainable management of valuable ecosystems and eco-friendly human approaches to mitigate wetland degradation.
 
 Keywords: Change detection, Land cover, Muthurajawela marsh, Negombo Lagoon, Wetland

SARSNet—A Novel CNN Approach for SARWater Body Segmentation

This paper presents the SARSNet architecture, developed to address the growing challenges in Synthetic Aperture Radar (SAR) deep learning-based automatic water body extraction. Such a task is riddled with significant challenges, encompassing issues like cloud interference, scarcity of annotated dataset, and the intricacies associated with varied topography. Recent strides in Convolutional Neural Networks (CNNs) and multispectral segmentation techniques offer a promising avenue to address these predicaments. In our research, we propose a series of solutions to elevate the process of water body segmentation. Our proposed solutions span several domains, including image resolution enhancement, refined extraction techniques tailored for narrow water bodies, self-balancing of the class pixel level, and minority class-influenced loss function, all aimed at amplifying prediction precision and streamlining computational complexity inherent in deep neural networks. The framework of our approach includes the introduction of a multichannel Data-Fusion Register, the incorporation of a CNN-based Patch Adaptive Network augmentation method, and the integration of class pixel level balancing and the Tversky loss function. We evaluated the performance of the model using the Sentinel-1 SAR electromagnetic signal dataset from the Earth flood water body extraction competition organized by the artificial intelligence department of Microsoft. In our analysis, our suggested SARSNet was compared to well-known semantic segmentation models, and a comprehensive assessment demonstrates that SARSNet consistently outperforms these models in all data subsets, including training, validation, and testing sets.

SARSNet—A Novel CNN Approach for SARWater Body Segmentation

This paper presents the SARSNet architecture, developed to address the growing challenges in Synthetic Aperture Radar (SAR) deep learning-based automatic water body extraction. Such a task is riddled with significant challenges, encompassing issues like cloud interference, scarcity of annotated dataset, and the intricacies associated with varied topography. Recent strides in Convolutional Neural Networks (CNNs) and multispectral segmentation techniques offer a promising avenue to address these predicaments. In our research, we propose a series of solutions to elevate the process of water body segmentation. Our proposed solutions span several domains, including image resolution enhancement, refined extraction techniques tailored for narrow water bodies, self-balancing of the class pixel level, and minority class-influenced loss function, all aimed at amplifying prediction precision and streamlining computational complexity inherent in deep neural networks. The framework of our approach includes the introduction of a multichannel Data-Fusion Register, the incorporation of a CNN-based Patch Adaptive Network augmentation method, and the integration of class pixel level balancing and the Tversky loss function. We evaluated the performance of the model using the Sentinel-1 SAR electromagnetic signal dataset from the Earth flood water body extraction competition organized by the artificial intelligence department of Microsoft. In our analysis, our suggested SARSNet was compared to well-known semantic segmentation models, and a comprehensive assessment demonstrates that SARSNet consistently outperforms these models in all data subsets, including training, validation, and testing sets.

High Structural Diversity of Aeruginosins in Bloom-Forming Cyanobacteria of the Genus Planktothrix as a Consequence of Multiple Recombination Events.

Many compounds produced by cyanobacteria act as serine protease inhibitors, such as the tetrapeptides aeruginosins (Aer), which are found widely distributed. The structural diversity of Aer is intriguingly high. However, the genetic basis of this remains elusive. In this study, we explored the genetic basis of Aer synthesis among the filamentous cyanobacteria Planktothrix spp. In total, 124 strains, isolated from diverse freshwater waterbodies, have been compared regarding variability within Aer biosynthesis genes and the consequences for structural diversity. The high structural variability could be explained by various recombination processes affecting Aer synthesis, above all, the acquisition of accessory enzymes involved in post synthesis modification of the Aer peptide (e.g., halogenases, glycosyltransferases, sulfotransferases) as well as a large-range recombination of Aer biosynthesis genes, probably transferred from the bloom-forming cyanobacterium Microcystis. The Aer structural composition differed between evolutionary Planktothrix lineages, adapted to either shallow or deep waterbodies of the temperate climatic zone. Thus, for the first time among bloom-forming cyanobacteria, chemical diversification of a peptide family related to eco-evolutionary diversification has been described. It is concluded that various Aer peptides resulting from the recombination event act in chemical defense, possibly as a replacement for microcystins.

Dynamic responses of the end-anchored floating bridge under the combined action of wind and waves

Long floating bridges offer a highly advantageous approach for crossing extensive and deep waterbodies. However, the multifaceted marine environment emphasizes the necessity of exploring the dynamic behavior of floating bridges under diverse load conditions. This study experimentally investigates the dynamic response of an end-anchored floating bridge under the combined action of wind and waves. A truncated model was designed with a geometrical scale of 1:100, and a series of trials were conducted, including the wind-only, wave-only, and wind-wave cases. The focus of the study was on the sway, heave and roll responses. Experimental results revealed that the coupling effect of wind and waves could increase the vulnerability of floating bridges. In the wind-wave cases, the dynamic response was categorized into distinct wind-controlled and wave-controlled zones. The mean response was predominantly influenced by wind loads, while the response standard deviation was significantly affected by wave loads. An analysis of the probability density function of motion response showed that the coupling effect in high-velocity wind cases amplified motion response amplitudes and broadened the distribution range. This study significantly advances the comprehension of the coupled behavior of floating bridge motion responses in wind-wave environments, offering valuable insights for the design of floating bridges.

LATE GLACIAL AND HOLOCENE HISTORY OF LAKE BOLSHOE MIASSOVO (SOUTHERN URALS) BASED ON DIATOM ANALYSIS OF BOTTOM SEDIMENTS<a href="#FN1"><sup>1</sup></a>

Bottom sediments are the most important “archive” containing information about the development of lake ecosystems. One of the most reliable and widely used methods of studying bottom sediments is diatom analysis (Juze et al., 1949). Currently, it is part of a group of guiding methods used to reconstruct the historical dynamics of the environment and climate (Rudaya et.al., 2012; Palagushkina et.al., 2018). In this work, the history of development of Lake Bolshoe Miassovo (Southern Urals) reconstructed using the taxonomic composition of diatoms found in the 526 cm long sediment core is presented. The maximum age of the sediments in the column was 13 500 years BP. According to the results of the study, 123 taxa of diatoms belonging to 47 genera were identified in the lake sediments. Diatom analysis of the bottom sediments of the studied lake allowed us to identify the main stages of the evolution of the reservoir during the Late Glacial and Holocene. During ~13 200–11 700 yr BP, in the period of a cool climate, the lake was a deep body of water with a constant water level and an extensive zone of shallow waters overgrown with macrophytes; then ~11 700–8500 cal. years BP against the background of cooling, the water level decreased; from ~8500–4600 cal. years BP was the stage of increasing water level in the lake in a warmer and wetter climate; in the period ~4600–2500 cal. years BP there was an increase in productivity of algal communities; during ~2500–800 cal. years BP against the background of decreasing temperature, a deep lake with low mineralized water, and presence of swampy shallow waters with acidification processes in them is finally formed.

Response of Dissolved Trace Metals to Dust Storms, Sediment Resuspension, and Flash Floods in Oligotrophic Oceans

AbstractTrace metals (TM) delivered by atmospheric dust play a key role in oceanic biogeochemical cycles. However, the impact of short‐term environmental perturbations such as dust storms and sediment resuspension events on the oceanic water column is poorly constrained due to the low temporal sampling resolution and episodic nature of these events. The Gulf of Aqaba (GoA), Red Sea, is a highly accessible deep oligotrophic water body featuring exceptionally high atmospheric deposition fluxes that provide the main source of TMs to the GoA surface water. Here, we present a 2‐year time series of dissolved manganese, cobalt, nickel, copper, zinc, cadmium, and phosphate concentration profiles sampled in the GoA. The study focuses on daily time scale dust storms and episodes of sediment resuspension to quantify the immediate impact of these events on dissolved TM cycling. Counter‐intuitively, upper mixed layer TM inventories decrease with increasing aerosol loads, with the effects of aerosol‐induced TM scavenging and dissolution peaking 5–6 days after aerosol deposition. Dust storms promote intense TM scavenging, with TM inventories decreasing by up to 44%, but seldom lead to TM enrichment. Similarly, sediment resuspension and flash flood events triggered significant TM scavenging. These findings highlight the potential dual role of atmospheric deposition in the oceans as a long‐term source of dissolved TMs and a short‐term sink. The in situ observations presented here may be used to understand and quantify the global impact of abrupt environmental events on oceanic chemical compositions.

A mechanistic approach for interpreting hydroclimate from halite‐bearing sediments

ABSTRACTEstablishing accurate palaeo‐hydroclimatic reconstructions from lacustrine and marine archives is a long‐standing challenge in palaeoenvironment studies. Closed‐basin evaporites, and especially halite, record episodes of extremely arid conditions during rapid climate change. However, the complex limnological behaviour of deep hypersaline water bodies and the stochastic nature of the hydroclimatic regime and its variations limit detailed palaeo‐hydroclimatic interpretations from such records. Therefore, a mass‐balance model was developed to explore hydrology–limnology–sedimentology relationships in hypersaline environments under both deterministic and stochastic approaches that generates synthetic halite–mud sequences. Applying the model to the Holocene Dead Sea halites yields novel insights into palaeoenvironmental conditions in the Levant. The deterministic framework indicates that: (i) under a series of similar hydroclimatic cycles, the thickness of each subsequent halite interval decreases, due to the depletion of dissolved‐ions storage in the brine; (ii) halite deposition requires lake levels to drop below the minimal lake level of the preceding cycle; (iii) the time interval between halite deposition and the hydrological minimum is increasingly longer in subsequent cycles. Thus, counter‐intuitively, halite deposition mostly takes place as water discharge increases, providing that the water balance is still negative. The stochastic approach produced random sequences comparable to the observed Dead Sea sedimentary record. It demonstrates that some hydrological minima are not represented by halite deposition at all. Furthermore, the thickness and number of halite beds at each hydrological cycle vary substantially, depending on the specific hydrological conditions realized. Finally, these results imply that the major Dead Sea level drop at the pre‐Holocene deglaciation (ca 14 ka bp), previously assumed to be a record minimum, could not have been as pronounced as suggested, and must have been milder than the subsequent drop at the early Holocene (ca 11–10 ka bp).

Revealing the response of urban heat island effect to water body evaporation from main urban and suburb areas

The urban heat island (UHI) effect is accelerated with urbanization and climate change, thus threatening human survival. The evaporation from water body (E) takes away energy through heat absorption process, thereby effectively play a role in temperature cooling and UHI effect alleviation. However, the response of UHI effect to urban E is still lacks study in the current UHI research. To address this issue, this work proposes a customized water body evaporation model in urban areas. The newly developed urban E model considers the contribution of anthropogenic heat flux (AHF) to the energy balance in urban areas. Meanwhile, AHF is also used to enhance the simulation of the water heat storage change (G) for urban water body. Validation results in two megacities in China indicate that the developed urban E model which considered AHF in the energy balance equation significantly improves the simulation performance of E in the main urban area (the root mean square error (RMSE) significantly decreased by 26.6 W/m2 compared with the original Penman formula for E in the main urban area (Eu) simulation). The consideration of AHF in the G determination improves the simulation performance of E in the deep water body (the RMSE significantly decreased by 33.3 W/m2 compared to the AHF-Penman model that do not considering G for E simulation in deep water body). The developed urban E model is further used to evaluate the response of UHI to the Eu and E in the suburban area (Es). It is found that Eu effectively alleviates UHI, while Es aggravate UHI. Moreover, the cooling effect of E in the main urban areas (ΔTau) and suburbs (ΔTas) are increased with urbanization. The increasing rate of ΔTau is higher than ΔTas, indicate the contribution of evaporation cooling to the UHI alleviation is increased with urbanization. Further analysis demonstrate the urbanization process can explain approximately 90% of the enhanced ability of E to mitigate the UHI effect. Correlation analysis shows that the mitigation capability of E to UHI effect is mainly controlled by the volume and surface size of water body. Finally, future climate scenario-based urban E forecast confirms that ΔTau and ΔTas will continue to rise with climate change. The average increasing rate are 0.018 °C/year and 0.013 °C/year for ΔTau and ΔTas, respectively, under the three representative concentration pathways. The increasing rate of ΔTau is larger than ΔTas, suggesting the mitigation of the UHI effect will benefit more from urban E under the future climate change. Generally, our findings highlight that the mitigation of the UHI effect mainly benefits from E in the main urban area rather than E in the suburban area. This study gains insight into E in urban areas, including its algorithm, interaction with the UHI effect, and responses to urbanization and climate change. The results of this study provide a good scientific basis for urban landscape water planning.

Evaluation of water quality pollution and analysis of vertical distribution characteristics of typical Rivers in the Pearl River Delta, South China

Water quality comprehensive evaluation is an essential technical measure for water environment management and treatment. The previous research methods were often insufficient for studying black-sticking water bodies' formation and transformation mechanisms. In view of this, the single pollution index method and the comprehensive water quality identification index method (Iwq) were used to evaluate the pollution characteristics of rivers; the main pollution factors and sources of the watershed were determined by principal component analysis (PCA), and the vertical stratification characteristics of the water bodies were analyzed. The results showed that the total nitrogen (TN) values of pollutants in typical rivers in the Pearl River Delta were higher than the class V water quality standard, and the ammonia nitrogen (NH3−N) pollution level was the second-highest. TN concentration ranges from 4.27 to 19.83 mg/g, and NH3-N concentration ranges from 2.44 to 15.37 mg/g. In addition, in the monitoring of 15 rivers, 11 of them were the inferior V surface water, including five rivers' comprehensive water quality categories for black-stinking water bodies. This may be related to the process of water self-purification and pollutant transport, and rivers in densely populated areas are often subject to discharge from domestic sewage and industrial sewage. The results of the PCA extracted three principal components (PC), accounting for 88.825% of the total variance, with the first and third PCs controlled by human activities and the second PC influenced by natural sources. There is a more apparent vertical stratification of water bodies here in the typical rivers of the Pearl River Delta, and DO was an important factor affecting the vertical distribution of chemical oxygen demand (COD), NH3-N, TN, total phosphorus (TP), sulfide, Ferrum (Fe), and manganese (Mn). The severe lack of DO in deep water bodies led to elevated levels of NH3-N, Fe, and Mn, and gases such as hydrogen sulfide was released under anaerobic conditions, resulting in eutrophication and black-sticking levels in water bodies.

Development of a 60-year high-resolution water body evaporation dataset in China

Evaporation from water bodies (Ew) is a critical component of the global water cycle. However, existing evaporation products that include Ew often suffer from drawbacks such as coarse resolution, short time span, and high uncertainty. This study developed a 60-year (1960–2019) high-resolution (0.05º×0.05º) evaporation dataset for small shallow water bodies in China based on the Penman model. Two key factors affecting the accuracy of the Penman model were considered: the uncertainty of the empirical wind function and changes in heat storage in the water body. Specifically, we used large-size (20 or 100 m2) pan evaporation (Epan) observations from 21 sites as a benchmark to correct the wind function of the Penman model. A data-driven model was then developed to map the spatial distribution of the wind function coefficients across China. The corrected wind function significantly improved the accuracy of Epan estimates compared to the original wind function, with the Kling-Gupta efficiency (KGE) increased by 0.05∼0.10. To model the effect of heat storage changes on evaporation, an equilibrium temperature method was used. We also introduced an area-dependent scaling factor into the wind function to account for the effect of water body's size on Ew estimation. The reliability of the Ew algorithm was tested on two lakes using eddy-covariance flux observations, and simulations showed good agreement with observations. The Epan (20 m2 pan) dataset and its two components calculated from the radiative and aerodynamic terms of the Penman model can be accessed at https://osf.io/qd28m/. Users can utilize the two Epan components and the area-dependent scaling factor to estimate evaporation for water bodies of varying sizes. However, caution is needed when applying this dataset to deep water bodies, as it is designed for shallow water bodies.

Description of two new species of apple snail (Ampullariidae: Pomacea) from Peruvian Amazonia

Two new species of apple snails are described, Pomacea penai sp. nov. and Pomacea reevei sp. nov. that are used as food resources in Peruvian Amazonia. We used anatomical and conchological features to diagnose these two species. Pomacea penai sp. nov. is characterized by a highly variable shell morphology, spire that is prominent to immersed, apical penis sheath gland covering 1/3 penis sheath and elongated basal gland, prostate broad proximally, reduced stomach septum, green eggs, and commonly inhabits temporary flooded areas, creeks, and oxbow lakes. Pomacea reevei sp. nov. possesses a large shell, ranging from 81-137 mm, grey broad penis sheath, small apical penis sheath gland and the basal gland covering 1/3 penis sheath, tall stomach septum, white eggs, and found in deep lentic water bodies.

Two-way coupled long-wave isentropic ocean-atmosphere dynamics

The events following the 15 January 2022 explosions of the Hunga Tonga-Hunga Ha'apai volcano highlighted the need for a better understanding of ocean-atmosphere interactions when large amounts of energy are locally injected into one (or both). Starting from the compressible Euler equations, a two-way coupled (TWC) system is derived governing the long-wave behaviour of the ocean and atmosphere under isentropic constraint. Bathymetry and topography are accounted for along with three-dimensional atmospheric non-uniformities through their depth average over a spherical shell. A linear analysis, yielding two pairs of gravito-acoustic waves, offers explanations for phenomena observed during the Tonga event. A continuous transcritical regime (in terms of water depth) is identified as the source of large wave generation in deep water bodies, removing the singularity-driven Proudman-type resonance observed in one-way coupled models. The refractive properties, governing the interaction of the atmospheric wave with step changes in water depth, are derived to comment on mode-to-mode energy transfer. Two-dimensional global simulations modelling the propagation of the atmospheric wave (under realistic conditions on the day) and its worldwide effect on oceans are presented. Local maxima of water-height disturbance in the farfield from the volcano, linked to the atmospheric wave deformation (in agreement with observations), are identified, emphasising the importance of the TWC model for any daylong predictions. The proposed framework can be extended to include additional layers and physics, e.g. ocean and atmosphere stratification. With the aim of contributing to warning system improvement, the code necessary to simulate the event with the proposed model is made available.

Analysis of Water-Lifting Aerator Performance Based on the Volume of Fluid Method

Water quality deterioration is a major problem faced by reservoirs globally, owing to the inflow of pollution from industrial and municipal activities. Water-lifting aeration is an in situ water quality improvement technology that mixes and oxygenates deep water bodies in reservoirs to improve pollution control efficiency and water quality. While previous studies have mainly focused on the mixing process in the reservoir outside the water-lifting aerator (WLA), knowledge of the internal flow remains limited. In this study, a two-phase flow within a WLA system was numerically studied using the volume of fluid (VOF) method to comprehensively analyze the internal two-phase flow characteristics and the influence on the water-lifting and oxygenation performance of the system. The statistical analysis results showed that increasing the aeration chamber volume enhanced the bottom oxygenation performance by 27% because of the prolonged time of the deflector plate outlet outflow. Additionally, increasing the air release rate enhanced the water-lifting performance by 47%, which was induced by the shortened air piston release period. This study demonstrates the internal flow mechanism of the WLA and provides technical support for parameter optimization design, which has significant scientific research and engineering application value.

Rapid and unplanned urbanization in the least developed districts of Bangladesh: a case study from Jamalpur using geospatial techniques

Sustainable urban development is a key compoment in the United Nation’s Sustainable Development Goals. Monitoring urbanization is critical for planners, governments and non-governmental organizations, and scientists to design policies that maximize the use of natural resources and accommodate development while reducing environmental effects. This research aims to analyze how urbanization patterns have changed in the largely unknown least developed regions of Bangladesh. Multispectral satellite imageries over 30 years (1991 to 2021) were used to analyze the urbanization pattern of Jamapur district. Utilizing object-based image classification and on-field validation for seven Land Use and Land Cover classes, it was found that built-up area expanded by 748.92% during the past three decades while depleting bare soil (− 97.65%), deep waterbody (− 79.33%), shallow waterbody (− 8.46%), light vegetation (− 14.28%) and agricultural land (− 26.33%).. Because of increased in built-ups, the land surface temperatures (LST) were also increased over the study period (the minimun recorded LST were 12.84 °C, 15.89 °C, 15.8 °C and 17 °C while the maximun LST were 17.93 °C, 23.7 °C, 23.79 °C and 26.73 °C for the year of 1991, 2001, 2013 and 2021 respectively). This study will act as a baseline for future studies It be insightful to urban planners and policymakers in developing countries regarding urban sustainability and minimizing urban risks and hazards in the least developed districts.

THE BEHAVIOUR OF PHOSPHORUS IN AN OLD PARALLEL CHANNEL SLAŇÁKY IN THE POODŘÍ (CZECH REPUBLIC)

Within the Poodří nature reserve and the Odra River old parallel channel, Slaňáky, various forms of phosphorus were investigated due to increased high concentrations of total phosphorus (Ptot) in the surface water. Surface water samples were subjected to chemical analyses using absorption spectrophotometry (Ptot and P-PO43- ) and accompanying parameters (t, O2, pH, Cond, TSS ) were measured. Next, grain size analysis of the sediment and sediment analyses using X-ray fluorescence were carried out (P, Fe, Al, Ca, Si, K, Mn, S, etc.). The seasonality of Ptot concentrations in the water was not confirmed, the reservoir behaved as a pool. The concentrations of the dissolved inorganic form P- PO43- were low when compared to Ptot, thus suspended phosphorus prevailed. This may be related to the low depth of the given water body, where stratification does not occur in contrast to deep water bodies. However, sediment resuspension is frequent, and phosphorus largely accumulates. The concentrations of Ptot in the sediment ranged around 4900 mg/kg, where the inorganic form prevailed (87.24 – 93.73 %) over the organic (6.27 – 12.76 %). At the same time, the sediment samples were abundant for sand fractions (2 – 0.03 mm), 47.86 – 60.89 %, and finest silt and clay (< 0.063 mm), 33.07 – 44.60 %.