Increase In Water Level Research Articles

Dynamics of beach scarp formation behind detached breakwaters

Detached (offshore) breakwaters are widely used as beach stabilization measures. However, there is potential for erosion at the openings between detached breakwaters, which may result in the formation of beach scarps. This study evaluated the formation of beach scarps around breakwaters using field surveys and numerical simulations. The evaluation was conducted using a combination of a recent advanced field survey method and a numerical modelling system combining GPV-MSM, SWAN, and XBeach. The unmanned aerial vehicle photogrammetry results revealed the height of the beach scarp generated behind the detached breakwaters to be approximately 3.0 m at Aoyama beach, Niigata coast, Japan, although sand deposition occurred below sea level towards the detached breakwaters. The numerical simulation using the results of the field survey showed that a combination of high waves and increased water level owing to radiation stress between the shoreline and breakwaters resulted in a steeper slope in the beach morphology. Second, avalanching occurred on the beach, leading to the formation of beach scarps. This study showed that detached breakwaters may lead to high water levels, resulting in the generation of beach scarps behind the breakwaters. This study implied that large beach scarps can be generated even when detached breakwaters are constructed.

Estimation of Groundwater Storage Change and Groundwater Recharge Using GRACE data in Jedeb Watershed Under the Application of Google Earth Engine

Over exploitation of Ground Water (GW) has resulted in lowering of water table in the Jedeb watershed. In this study, water storage changes with GRACE satellite data and total annual precipitation with CHIRPS data in the Google Earth Engine system were investigated for the Jedeb watershed during 2003–2017. The groundwater recharge is estimated from a time series of groundwater storage using the water table fluctuation method. According to the results obtained from the GRACE satellite data on the fluctuations of annual water storage between 2003 and 2017, it was found that the biggest annual increase in water levels (15 cm) occurred in 2008, 2013, and 2015, and the biggest annual decrease (12.5 cm) occurred in 2012. The obtained net recharge rate varied from 18 to 25 cm/year for a 14-year period, and the average was 21 cm/year. This study indicates that the GRACE-based estimation of groundwater storage changes is skilled enough to provide monthly updates on the trend of groundwater storage changes for resource managers and policymakers in the Jedeb watershed.

Combined influence of extreme flooding-induced water level increase and N and P inputs on the submerged macrophyte <i>Vallisneria natans</i>

Combined influence of extreme flooding-induced water level increase and N and P inputs on the submerged macrophyte <i>Vallisneria natans</i>

Relative Sea Level Rise in the Winyah Bay-Waccamaw River Tidal System Over the Last Thirteen Years

Prediction of sea level rise (SLR) in response to climate change has been the focus of worldwide research, most focusing on the impact by human development. The research has been limited to estuaries and tidal rivers near harbors dealing with the hydrodynamics of reversing tidal flows. This article focuses on the Waccamaw River National Wildlife Refuge in coastal South Carolina where freshwater unidirectional flow is common. We examined the record of water levels in the Waccamaw and Pee Dee Rivers over the period 2007–2019 and the length of record of the United States Geographical Survey (USGS) gauge at Pawleys Island on the Waccamaw River. The Atlantic Ocean, off the southeastern coast of the US, has experienced accelerated SLR since 2000. National Oceanic and Atmosphere Administration (NOAA) tide gauges from Fort Pulaski on Cockspur Island in Georgia to Beaufort, North Carolina, show significant increase in long-term SLR since then with an average since 2007 of approximately 10 mm y-1. Since the study period was less than the 18.6-year cycle of lunar precession, tidal ranges were expanding for much of the study period resulting in the rate of rise of Mean Higher High Water (MHHW; the average of the highest tide levels during each day) being greater than the rate of increase of Mean Lower Low Water (MLLW; the average of the lowest tide levels during each day) in all ocean stations. We examined water levels at NOAA and USGS gauges from Oyster Creek, in North Inlet to Conway on the Waccamaw River and Near Bucksport on the Pee Dee River. We found mean water levels increased more rapidly with distance from the ocean with an apparent SLR > 40 mm y-1 at Conway on the Waccamaw and Bucksport on the Pee Dee. In contrast to the ocean NOAA gauges, the estuary/river gauges showed more rapid increase of daily minimum water level (an approximation of MLLW) than daily maximum water level (an approximation of MHHW) with an extreme of apparent rise of minimum water levels of 58 mm y-1 at Bucksport on the Pee Dee. Nearly 50% of the increase in apparent SLR was due to an increase in the annual average freshwater flow of the Pee Dee and Waccamaw Rivers. Over the past 13 years the Waccamaw National Wildlife Refuge has experienced an apparent SLR that was more than double that observed at the edge of the ocean. The rise has been greater in the height of daily low water than in the height of daily high water. The increase was driven by both tidal hydrodynamics and an increase in the rate of flow in the Pee Dee and Waccamaw Rivers. These findings have important implications for land managers, policymakers, and homeowners in the region as people in the middle to upper estuaries need to plan for rates of relative SLR rise much greater than the frequently discussed rates in the ocean.

Development and Deployment of a Virtual Water Gauge System Utilizing the ResNet-50 Convolutional Neural Network for Real-Time River Water Level Monitoring: A Case Study of the Keelung River in Taiwan

Climate change has exacerbated severe rainfall events, leading to rapid and unpredictable fluctuations in river water levels. This environment necessitates the development of real-time, automated systems for water level detection. Due to degradation, traditional methods relying on physical river gauges are becoming progressively unreliable. This paper presents an innovative methodology that leverages ResNet-50, a Convolutional Neural Network (CNN) model, to identify distinct water level features in Closed-Circuit Television (CCTV) river imagery of the Chengmei Bridge on the Keelung River in Neihu District, Taiwan, under various weather conditions. This methodology creates a virtual water gauge system for the precise and timely detection of water levels, thereby eliminating the need for dependable physical gauges. Our study utilized image data from 1 March 2022 to 28 February 2023. This river, crucial to the ecosystems and economies of numerous cities, could instigate a range of consequences due to rapid increases in water levels. The proposed system integrates grid-based methods with infrastructure like CCTV cameras and Raspberry Pi devices for data processing. This integration facilitates real-time water level monitoring, even without physical gauges, thus reducing deployment costs. Preliminary results indicate an accuracy range of 83.6% to 96%, with clear days providing the highest accuracy and heavy rainfall the lowest. Future work will refine the model to boost accuracy during rainy conditions. This research introduces a promising real-time river water level monitoring solution, significantly contributing to flood control and disaster management strategies.

Water table level dynamics in the drained part of the great Vasyugan mire

Relevance. The need to assess mire-river interaction in Western Siberia under the influence of drainage and the pyrogenic factor. Aim. To study water table level dynamics in the Great Vasyugan Mire and the patterns of its change under the influence of drainage and the pyrogenic factor. Objects. Nоrtheastern part оf the Great Vasyugan Mire clоse tо Pоlynyanka village, Bakchar district, Tоmsk regiоn. Methods. Hydrological monitoring of drained and pristine part of the Great Vasyugan Mire is organized within the small model catchments of the Gavrilovka River and Klyuch River in the Vasyugan station of the Siberian Research Institute of Agriculture and the Peat branch of the Siberian Research Institute оf Agriculture and Peat RAS. Water table level monitoring was carried out in 2022 using Solinst Levelloger (Canada) with a frequency of 1 hour. River discharge measurements were made in different water periods using an acoustic current meter OTT Hydromet. The research methodology included an assessment of the spatial and temporal variation in water levels over the drained territory of the Great Vasyugan Mire in the Gavrilovka River basin in comparison with pristine part and depending on the main meteorological factors, correlation curves construction of mire water level and river discharges, the specific yield calculation. Statistical analysis of the data was carried out using the nonparametric Wilcoxon test, correlation and cluster analysis. Results. The studies shown that the drained area of the Great Vasyugan Mire within the Gavrilovka River basin is characterized by a significant transformation of the hydrological regime; there is a significant decrease in the water levels and an increase in the amplitude of their fluctuations. The influence of the pyrogenic factor is expressed in a certain increase in water levels as a result of the surface burnout and the leveling of microtopography. An analysis of the spatial variation of the water levels showed that it depends on the vegetation type of key sites, the slope of the surface, and the degree of surface burnout. It also depends on the location of the site relative to the lagg area, zones of backwater flow formed near overgrown drainage ditches, dirt roads and main ditch drainage zones. As a result of the forest reclamation and fire event in the study area of the Great Vasyugan Mire, active decomposition of plant residues was noted. This led to a decrease in the storage capacity (specific yield) of the upper peat layer. A decrease of the specific yield will increase the runoff from the mire area, which means the increase of possibility of extreme hydrological events in the conditions of growth in the amount of precipitation.

Lower Crust Viscosity in Central Tibet Inferred From InSAR Derived Deformation Around Siling Co Lake After Its Rapid Expansion in the 2000s

AbstractConstraining the lithospheric rheology of Tibetan Plateau is important for the physical understanding of its tectonics. Siling Co, the largest high‐altitude lake in the world, has experienced a rapid water level increase in the 2000s. The resulting loading changes stimulate the viscoelastic response of the lower crust, giving access to study the lithospheric rheology in central Tibet. Here, we derive a clear subsidence signal around the lake with peak velocity of 4 mm/yr from two tracks of Sentinel‐1 InSAR images acquired from 2017 to 2022. Our viscoelastic modeling suggests a ductile layer 15 km beneath the surface with a decadal‐scale, steady‐state viscosity of 1–4 × 1019 Pa s. This value is consistent with the viscosity inferred from millennium‐scale shoreline changes, but is about 10 times higher than the viscosities derived from the deformation surrounding Siling Co before 2011, highlighting the role of transient viscosity in controlling the surface deformation.

Three-dimensional hydro-mechanical coupling numerical simulation of shield-driven cross-river twin tunnels: A case study

With the rapid development of urban underground space, the construction of shield-driven cross-river twin tunnels is increasing, and the complex hydro-mechanical coupling effects and twin-tunnel interactions bring huge construction risks to such projects, which have attracted more and more attention. This study aims to understand the excavation effects induced by shield driving of cross-river twin tunnels through numerical simulation. A refined three-dimensional numerical model based on the fully coupled hydro-mechanical theory is established. The model considers the main components of the slurry pressure balance shield (SPBS) machine, including support force, jacking thrust, grouting pressure, shield-rock interaction and lining-grouting interaction, as well as the detailed construction process. The purpose is to examine the excavation effects during construction, including rock deformation around tunnels, the change in pore pressure, and the response of the lining. The results show the influence range of twin-tunnel excavation on rock deformation and pore pressure, as well as the modes of lining response. In addition, this study also systematically investigates the effects of water level fluctuation and burial depth on twin-tunnel excavation. The results indicate that the increase of water level or burial depth will enhance the excavation effects and strengthen the twin-tunnel interactions. These results provide useful insights for estimating the construction impact range and degree of twin tunnels, and serve as basic references for the design of cross-river twin tunnels.

Analysis of the Relationship Between Shallow Water, Flood, and Tsunami

Contemporarily, it is necessary to delve into the intricate connections between shallow water dynamics, flood events, and tsunamis, elucidating their pivotal role in disaster management and environmental studies. This study explores how shallow water conditions influence the behavior of floods and tsunamis through recent advancements, numerical modeling, and observational techniques. The framework of the study involves an examination of the fundamental concept of shallow water, its characteristics, and its influence on wave behavior, sediment transport, and coastal interactions. The study subsequently analyzes the interplay between shallow water and floods, emphasizing the rapid increase in water levels as floodwaters approach shallower areas, contributing to coastal inundation. Similarly, the investigation explores how shallow water dynamics amplify tsunami wave heights and impact, particularly in coastal settings with complex features. By employing advanced simulations and real-world data, the study substantiates the crucial role of shallow water in shaping flood and tsunami risks. While acknowledging limitations, the research concludes by underscoring the implications of these relationships for disaster preparedness, environmental protection, and community resilience. The study contributes to a comprehensive understanding of the profound effects of shallow water dynamics on catastrophic events and highlights the importance of factoring these dynamics into effective disaster management strategies.

Comparative flooding tolerance of Typha latifolia and Phalaris arundinacea in wetland restoration: Insights from photosynthetic CO2 response curves, photobiology and biomass allocation

Tall helophytes such as Typha latifolia and Phalaris arundinacea often rapidly colonise after rewetting of former agricultural soil and are therefore often the first plants to contribute to the soil carbon pool. In this study we carried out a mesocosm experiment where these two species grew at three different water levels relative to the soil surface (−15 cm, 0 cm, +15 cm). After eight weeks' growth, measurements of photosynthetic CO2-response curves, stomatal conductance and chlorophyll fluorescence of photosystem II were carried out to detect flooding stress. After 10 weeks’ growth, the plants were harvested and biomass production, biomass allocation and specific leaf area were determined. T. latifolia had a higher and more stable photosynthetic performance across all water level treatments, which resulted in an overall higher aboveground and belowground production than P. arundinacea. In contrast, Vcmax and Jmax decreased by 41 % and 42 %, respectively from drained to flooded conditions with signs of flooding stress as impairment of the photosynthetic apparatus. Moreover, increasing water level resulted in maintenance of aboveground organs for P. arundinacea but a decrease in allocation to belowground organs. P. arundinacea did not invest in a higher specific leaf area to counter the decreased photosynthesis under flooding. From −15 cm to 0 cm water levels, P. arundinacea showed a 68 % reduction in belowground biomass, which has negative implication for carbon retention immediately after rewetting. In contrast, recolonization of T. latifolia is likely to be a suitable contributor to the soil carbon pool due to its stable physiology and high above- and belowground biomass production at all water depths, and also likely under natural water level fluctuations. We showed that even though both species are generally considered wetland plants, they are likely to support considerably different photosynthetic carbon assimilation and soil carbon sequestration rates.

Increasing marsh bird abundance in coastal wetlands of the Great Lakes, 2011–2021, likely caused by increasing water levels

Abstract Wetlands of the Laurentian Great Lakes of North America (i.e., lakes Superior, Michigan, Huron, Erie, and Ontario) provide critical habitat for marsh birds. We used 11 years (2011–2021) of data collected by the Great Lakes Coastal Wetland Monitoring Program at 1,962 point-count locations in 792 wetlands to quantify the first-ever annual abundance indices and trends of 18 marsh-breeding bird species in coastal wetlands throughout the entire Great Lakes. Nine species (50%) increased by 8–37% per year across all of the Great Lakes combined, whereas none decreased. Twelve species (67%) increased by 5–50% per year in at least 1 of the 5 Great Lakes, whereas only 3 species (17%) decreased by 2–10% per year in at least 1 of the lakes. There were more positive trends among lakes and species (n = 34, 48%) than negative trends (n = 5, 7%). These large increases are welcomed because most of the species are of conservation concern in the Great Lakes. Trends were likely caused by long-term, cyclical fluctuations in Great Lakes water levels. Lake levels increased over most of the study, which inundated vegetation and increased open water-vegetation interspersion and open water extent, all of which are known to positively influence abundance of most of the increasing species and negatively influence abundance of all of the decreasing species. Coastal wetlands may be more important for marsh birds than once thought if they provide high-lake-level-induced population pulses for species of conservation concern. Coastal wetland protection and restoration are of utmost importance to safeguard this process. Future climate projections show increases in lake levels over the coming decades, which will cause “coastal squeeze” of many wetlands if they are unable to migrate landward fast enough to keep pace. If this happens, less habitat will be available to support periodic pulses in marsh bird abundance, which appear to be important for regional population dynamics. Actions that allow landward migration of coastal wetlands during increasing lake levels by removing or preventing barriers to movement, such as shoreline hardening, will be useful for maintaining marsh bird breeding habitat in the Great Lakes.

Response of yellow perch to water level fluctuations in oligotrophic, north‐temperate inland lakes

AbstractInformation on yellow perch Perca flavescens population dynamics and responses to various abiotic and biotic factors in oligotrophic, north‐temperate inland lakes is limited. Water level fluctuations are known to influence available habitat and biological communities within the littoral zones of lakes, yet research is lacking for yellow perch in Wisconsin. The goal of our study was to characterize yellow perch population‐level responses to natural water level fluctuations in four northern Wisconsin lakes using a 39‐year time series. On average, increasing water level periods correlated with lower mean fyke net and gill net relative abundances (catch‐per‐unit‐effort), though generally not statistically significant. Yellow perch mean relative weight varied among lakes and was significantly greater during increasing water level periods for all lakes except one. The lack of statistically significant findings potentially suggests a buffering mechanism of north‐temperate oligotrophic lakes due to their small surface area to volume ratios, relative lack of nutrients, and(or) littoral structural habitat compared to other systems (e.g., shallow eutrophic lakes). Our results suggest that natural water level fluctuations may not be an environmental concern for yellow perch populations in some north‐temperate oligotrophic inland lakes.

Monitoring of the Surface Water Regime of the Sava River Alluvium in Serbia Using Geographic Information System (GIS) Techniques

In the spacious inundation area on the left bank of the lower course of the Sava River in Serbia, there is an abandoned meander Special Nature Reserve, “Obedska bara”, which represents a very important floodplain in this part of Europe. This area is characterized by an exceptional wealth of biodiversity with a significant presence of rare and endangered species of national and international importance. Hydrological conditions in the mentioned area were analyzed from the aspect of surface water movement in nature and conditions altered by human factors (after the construction of the road network, canals, etc.). The movement of surface water, i.e., the filling and emptying of the investigated area, parallel to the water level of the Sava River, is shown using a digital terrain model. Our simulation of the change in surface water level within the studied area included the display of underwater areas, both with the formation of a flood wave (i.e., increasing water level of the Sava) and with the outflow of water from the pond when the water level in the Sava was reduced in both scenarios (natural and conditions altered by human factors). GIS and terrain digitalization were used for geospatial and hydrological analyses and, based on this, maps that display endangered areas could be made. The obtained results show that the largest human impact was recorded at the water level of the Sava River 74 m above sea level. The aforementioned water regime changes were shown to negatively affect dominant vegetation, such as pedunculate oak and ash.

Model of Storm Surge Maximum Water Level Increase in a Coastal Area Using Ensemble Machine Learning and Explicable Algorithm

AbstractThis study proposes a novel, new ensemble model (NEM) designed to simulate the maximum water level increases caused by storm surges in a frequently cyclone‐affected coastal water of Hong Kong, China. The model relies on storm and water level data spanning 1978–2022. The NEM amalgamates three machine learning algorithms: Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and XGBoost (XGB), employing a stacking technique for integration. Six parameters, determined using the Random Forest and Recursive Feature Elimination algorithms (RF‐RFE), are used as input features for the NEM. These parameters are the nearest wind speed, gale distance, nearest air pressure, minimum distance, maximum pressure drop within 24 hr, and large wind radius. Model assessment results suggest that the NEM exhibits superior performance over RF, GBDT, and XGB, delivering high stability and precision. It reaches a coefficient of determination (R2) up to 0.95 and a mean absolute error (MAE) that fluctuates between 0.08 and 0.20 m for the test data set. An interpretability analysis conducted using the SHapley Additive exPlanations (SHAP) method shows that gale distance and nearest wind speed are the most significant features for predicting peak water level increases during storm surges. The results of this study could provide practical implications for predictive models concerning storm surges. These findings present essential tools for the mitigation of coastal disasters and the improvement of marine disaster warning systems.

Application of Ultra Fine Bubbles for Deoxygenation of Produced Water and Tap Water via Nitrogen Purging Scheme

In this study, we present our findings from examining a gas lift tower for produced and tap water de-oxygenation, applying the nitrogen purging at an ultra-fine bubble scale (18 μm average size). The experiments were conducted for produced water samples grafted with polyacrylamide concentration 300 ppm with a measured bulk viscosity of 5 mPa.s. Upon applying a series of experimental sets, 0 ppm DO was attained in all examined operational schemes (semi batch and once through) within various time limits, depending on the water level in the column. Considering the zero DO level as an objective function, the results showed an improvement of 5.7–14 folds in reaching the 0 ppm DO upon experimenting with the ultra-fine bubble purging in different schemes, compared with of the results obtained from the ordinary bubble size (mm scale). The results show that DO reached < 10 ppb within 23 minutes with nitrogen flowrate 3 L/min while DO reaching < 10 ppb within 28 minutes with nitrogen flowrate 5 L/min. Furthermore, implementing the ultra-fine bubble nitrogen purging was successful in running the de-oxygenation tower in a full continuous mode at a balanced inlet/outlet water flow rate. This has been done after reaching stability in the column operation (lasting around 1 hour for 422 L of examined water sample). The stable fine bubbles cloud in the column was quite efficient in treating water influent stream to be exited directly at 0 ppm DO within the same effluent flow rate. The treatment efficiency has shown an increase with increasing water level in the column, resulting in a denser layer/cloud of fine bubbles. This result suggests a unique approach/solution for the complete removal of DO from produced water, which is accounted effective to be adopted industrially

Numerical investigation of a district scale groundwater heat pump system: A case study from Colchester, UK

Nearly 40% of Europe’s total energy consumption is dedicated to buildings and heating/cooling make a significant part of this consumption. Groundwater heat pumps (GWHP) are highly efficient, and low-carbon technology that can supply heating/cooling to buildings on small or large scales. Thus, they contribute to achieving European targets of net-zero greenhouse gas emissions by 2050. In the literature, studies on the utilisation of GWHP at a district scale, particularly in chalk aquifers, are relatively rare. The implementation of district-scale geothermal heat pump (GWHP) systems poses several challenges, including dealing with the scale and complexity of the systems, addressing geological variability, managing high initial investments, balancing energy demand and supply, ensuring proper maintenance and monitoring, and mitigating potential environmental impacts. These challenges require careful consideration and strategic planning to ensure the successful deployment and sustainable operation of these systems., This study numerically investigates a district-scale GWHP system and analyses the thermal plume development created due to the heating operation, offering insights into system performance. A good match was found between field results and simulation results for water level increase and drawdown. However, there is a difference of approximately 11% in system efficiency between field tests and simulations due to the lower abstraction temperature detected in the simulation. The simulation results show that cooler water injection into the fractured chalk aquifer creates a thermal plume radially spanning out to 50 m. The thermal plume has no effect on the abstraction temperature and system performance. This result can be attributed to the large distance between injection and abstraction wells and the low hydraulic gradient.

Optimization of wetland water replenishment process based on the response of waterbirds in a semi-arid and cold region

Emergency ecological water replenishment(EEWR) has become a major strategy for recovering degraded wetland ecosystems worldwide. However, the actual replenishment process mainly depended on the tradeoff and experience between the managers of Taoer River and Xianghai Wetland, which is very random and lacks theoretical guidance. Thus, there is urge to assessing water replenishment effect on wetland and help to optimize the process. With contrasting results as different ecosystem elements respond differently, the optimization of water replenishment process should be based on the improvement of the ecosystem as whole rather than its separate elements. However, the dynamic monitoring of biotic and abiotic factors to reveal the complex relationships underlying their response can be challenging. Based on 6 years’ series data of migratory birds and environmental factors of Xianghai Wetland, which started emergency ecological water replenishment since 2004 and occurred frequently since 2011, the broader ecosystem response to water replenishment was analyzed using a multiple paths regression model and proposed an optimized scheme. The results showed that bird diversity was positively influenced by the increase in water area and vegetation was induced by ecological water replenishment. While the response of bird abundance to water replenishment varied with time, adequate open water in March was found to have a positive relationship with abundance by promoting vegetation germination and the reproduction of benthic organisms. High flow levels in the wet season (June–August) can negatively affect waterbird abundance by rapidly increasing water levels and inhibiting plant respiration, which leads to the reduction in feeding efficiency of waterbirds and biomass accumulation. Therefore, the existing ecological water replenishment time (May–September) is not suitable for bird abundance and should be advanced to spring (March–April). Given the antagonistic effect of flow on diversity and abundance, the total replenished water should be approximately 100 million m3. To avoid the negative influence of high water in the wet season, the allocation of water could be 0.3, 0.3, 0.2, and 0.2 million m3 in April, May, September, and October, respectively. These results scientifically support wetland protection and management.

Groundwater potentiality in hard-rock terrain of southern Saudi Arabia using electrical resistivity tomography approach

To detect groundwater-bearing zones in southern Saudi Arabia, 10 profiles of 2D electrical have been constructed resistivity tomography at five selected sites. The collected data were corrected and processed using the RES2DINV software. The results demonstrated that site-1 contains two groundwater-bearing zones; the first zone is situated 13 m beneath the ground surface, while the depth of the second zone varies from 4 m to 15 m. A promising 15-m-deep groundwater-bearing zone was identified at site 2. The groundwater-bearing zones exhibit depths of 40, 10, and 10 m at sites 3, 4, and 5, respectively. The detected groundwater-bearing zones are notably shallow, with a depth of 20 m below the ground surface and with lateral extension up to 200 m. These aquifers prevail in the alluvial deposits, where the weathered/fractured or fresh basement rocks underlying these aquifers. Moreover, rainfall recharges these unconfined aquifers, as evidenced by the increasing water levels along the main Wadi channels flow during rainy seasons. Sites 2, 3, and 5 are considered as groundwater-bearing sources with high potential. Because this unconfined aquifer can be swiftly replenished by the 300–360 mm of annual rainfall in the southern Saudi lowlands, it is a promising area for groundwater supply for future urbanization plans and agricultural projects in neighboring areas.

Rapid oscillation of sediment transport between the Bohai Sea and the Yellow Sea induced by Typhoon Lekima (2019)

Amidst the continued northward migration of tropical cyclones in the context of global warming, mid and high latitudes marginal seas, like the East China Seas in the northwest Pacific Ocean, are increasingly attacked by tropical cyclones. As such, it is crucial to pay more attention to the impact of tropical cyclones on these marginal seas. To address this issue, we utilized a well-calibrated FVCOM model to study the effects of Typhoon Lekima (2019) on sediment transport between the Bohai Sea and the Yellow Sea. The results showed that during Typhoon Lekima's passage, sediment dynamics in the Bohai and Yellow seas were significantly altered. During the first two days of Typhoon Lekima's arrival, the water and sediment transport pattern rapidly changed from normal summer conditions to a strong inflow into the Bohai Sea, which increased water levels in the southwest Bohai Sea. As Typhoon Lekima weakened, the barotropic effect drove the water outflow from the Bohai Sea to the Yellow Sea. Strong bottom shear stress induced by the high-energy waves introduced strong sediment resuspension, which led to massive sediment escaping out of the Bohai Sea via the outflow during the weakening period of Typhoon Lekima. After two days following Typhoon Lekima's passage, the transport pattern gradually returned to normal summer conditions. The study revealed that the net sediment load from the Bohai Sea to the Yellow Sea during Typhoon Lekima was approximately 0.84 Mt., which is equivalent to 5–33% of the annual flux. The study highlights the critical role of extreme weather events in sediment dynamics and provides important insights into the impacts of typhoon on source-to-sink process in mid and high latitude marginal seas.

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.