Water Level Changes Research Articles

Sedimentology and stratigraphy of the Jordan River Dureijat archeological site reveal subtle late Pleistocene water-level changes at Lake Hula, Jordan Valley, Israel

AbstractSedimentary records of environmental conditions retrieved from archeological sites provide valuable insight into the milieux of ancient humans and context to understand societal and cultural changes. At Jordan River Dureijat, an open-air site in Israel’s Hula Valley documenting the entire Epipaleolithic period as well as the Early Neolithic, sediments exposed on the walls of the excavation pit reveal a sequence of lacustrine deposits accumulated continuously between c. 21.1 and 11.3 cal ka BP near the southeast margin of Paleolake Hula. Through sediment-grain-size, geochemical, and paleontological analyses, we describe the nature of the Paleolake Hula from the Last Glacial Maximum (LGM) to the start of the Holocene. Until c. 17.2 cal ka BP, Paleolake Hula existed as a relatively large and well-buffered waterbody. A rapid and substantial drawdown of the lake occurred at 17.2 cal ka BP, followed by more frequent changes in the position of the shoreline in a smaller and shallower lake, resulting in the deposition of alternating near-shore and deeper lacustrine facies. Since the LGM, seven beds of structureless, silty sediments preserve archeological artifacts belonging to three Epipaleolithic cultures as well as the Early Neolithic pre-pottery Neolithic A culture. These sediments were deposited during phases of low lake level during which times humans waded into the shallow part of the lake, leaving behind stone and bone tools such as bladelets, lunates and burins, fishing hooks, line weights and net sinkers. Using radiocarbon-dated charcoal and a Bayesian statistical model, we produced a chronostratigraphic model for the archeological site, which enables the comparison of proxy paleoclimate records produced from this site’s sediments with regional archives as well as with global trends and changes in the Northern Hemisphere climate. Periods of low lake stands are correlated with the end of the LGM, Heinrich Event 1, and the beginning of the Younger Dryas Stadial. High water stands occurred contemporaneously with the peak of the LGM and during the Bølling–Allerød interstadial. This new water-level record from Lake Hula confirms that lake-level changes here broadly paralleled those of the Dead Sea and Sea of Galilee during the late Pleistocene, highlighting the importance of northern water sources to the overall water balance of the lakes along the Dead Sea Transform.

Correlation between <em>Phragmites australis</em> growth and seasonal lake level variations in Lake Maggiore (Italy/Switzerland): common reed management guidelines

The present study investigates the impact of water level regulation on the growth of common reed (Phragmites australis), a globally widespread helophytic plant. The investigation has been carried out in the Bolle di Magadino (municipalities of Locarno, Gambarogno, Gordola and Tenero; Ticino, Switzerland), a lacustrine-riparian nature reserve in the context of the Lake Maggiore (that stretches between Italy and Switzerland). This is an oligotrophic, artificially regulated lake. Our initial hypothesis was that variation in water table regulation is the most influential factor for explaining observed local reed dieback. To test this, culm height of P. australis was measured at each significant change in lake water level (water table height increase greater than 20 cm), or monthly in the case of a relatively constant lake level. The study took place between 2020 and 2022, monitoring 14 plots of 400 m2, placed at three different relative elevation classes with respect to the level of the lake (5 plots at low elevation, <193.475 m; 7 plots at intermediate elevation, 193.476-193.700 m; 2 plots at high elevation, >193.701 m). The results showed that P. australis growth is significantly influenced by the lake water level and thus the relative elevation of the stands, with lower lake levels leading to better growth, especially during the early phases of the growing season. On the other hand, prolonged flooding of shoots significantly impaired common reed growth. The study identifies two relevant relative elevation thresholds for winter mowing, a management practice that enhances reedbeds health. Mowing below 193.20 m elevation is considered risky, as no healthy reedbeds have been observed below this threshold. Mowing below an elevation of 193.50 m was defined as possibly risky, due to observed dieback in some areas as well as healthy reedbeds in other locations at the same or lower elevations. The research also discussed the potential impact of future changes in water level regulation, including the planned change in the spring regulation threshold (+1.50 m above the hydrometric zero in Sesto Calende). This is expected to result in a further rearrangement in lacustrine vegetation, with the growth optimum for P. australis becoming higher and an increase in clumping habit. In conclusion, this study provides valuable insights into the impact of water level regulation on the growth of P. australis in the Bolle di Magadino nature reserve. The research highlights the need for careful management of water level regulation to preserve the reedbed ecosystem and identifies relevant elevation thresholds for winter mowing to mitigate the risks of reed dieback. The findings can inform future management strategies for the Bolle di Magadino reserve and other similar ecosystems facing the challenges of artificial regulation of water levels.

Waterworld: The Use and Reuse of Lake Tadane in Safeguarding Knowledge and Sustaining the Cultural Heritage of the Nzulezo Community

Nzulezo, a tentative World Heritage Site listed in 2000 by UNESCO, is a community built on Lake Tadane in the Western Region of Ghana. Since its nomination, Nzulezo has become an attraction to both Ghanaians and foreigners alike. Over the years, the population has built dwellings and other structures to form the village over the lake, a way of adapting to an environment made up of about 70 per cent freshwater, about 20 per cent wetland, and 10 per cent land. Nzulezo stands out among heritage sites in Ghana due to its traditional architectural style. The village structures are made of wood and raffia. Located in a water-dominated environment, the community experiences changes in water levels that are predominantly seasonal. The water level is low from December to April during the dry season and high from June to August during the rainy season. In Nzulezo, the entire management of the site has been left to the Ghana Wildlife Society, a non-governmental organization (NGO). The focus of the management is tourism-driven, with less regard for the community members and the environment.

Assessing riverine fish community diversity and stability by eDNA metabarcoding

Monitoring and evaluating river ecosystems are of paramount importance in addressing ecological and environmental challenges. While eDNA (environmental deoxyribonucleic acid)-based method has emerged as a valuable tool for understanding these issues, its application in assessing phylogenetic diversity, community stability, and the identification of key species within river systems has been limited. In this study, we conducted eDNA metabarcoding to assess fish community phylogenetic diversity, species composition, assembly variations, and their relationship with hydrologic characteristics. We also explored ecological stability and the roles of key species in a river system comprising a mainstem (MS) and a tributary (TB) with distinct hydrologic features. Our findings uncovered previously unknown endemic fish species diversity, exemplified by the discovery of Triplophysa. We identified disparities in diversity, community composition, and assembly between the MS and TB. Furthermore, we established significant associations between water-level variations, water flow, and changes in community composition. Triplophysa, with its high diversity, played a pivotal role in the ecological network, contributing significantly to community stability. The loss of Triplophysa increased fragility in co-occurrence patterns. Comparing the ecological network of fish communities between the MS and TB, we found that the MS displayed greater robustness and lower vulnerability, with increased species competition likely promoting network stability. Overall, this study highlights the potential of integrating eDNA metabarcoding data for monitoring phylogenetic diversity, community structure, and variations in stability within fish communities.

Analysis of the Genetic Model of the Extremely Narrow Channel Shallow Water Delta in DL-A Oilfield, Bohai Bay Basin.

In recent years, the oil and gas reserves discovered in shallow water deltas in China have continued to grow. The research on shallow water delta deposition models and depositional genesis is becoming more and more mature. In this latest discovery, a unique type of extremely narrow channel shallow water delta deposit was found at the top of the V oil group in the lower part of the Minghuazhen Formation during the Neogene period at DL-A Oilfield, located in the Bohai Bay Basin. The width of most single channels in this deposit measures between 100 and 200m, which is relatively rare and differs from existing research. To better understand this unique narrow channel shallow water delta deposit, a range of analysis methods were conducted including trace element analysis, major element analysis, grain size analysis, core observation, casting thin section observation, 3D seismic analysis, and other methods. These analyses were used to determine the sedimentary environment and sedimentary genesis of the deposit in the study area. The results show the following: (1) The top of the V oil group in the lower part of Minghuazhen Formation was deposited with a strong oxidizing environment. In the early stage, the climate was dry and cold, and gradually changed to warm and humid in the late stage. (2) Due to the frequent exposure to the surface, obvious weathered surfaces and sedimentary discontinuities were observed on the cores; the particle size analysis shows that the lamina types developed in the study area are clastic-clay laminae and clay-clastic laminae, which are mostly developed in shallow lakes area. (3) Observations of cores and thin sections also indicated that the hydrodynamic conditions frequently changed in the study area, alternating between strong and weak hydrodynamic conditions in a short period due to the alternating occurrence of flood and dry periods during the rainy season. Weak hydrodynamic conditions and slow water flow result in insufficient undercutting and sidecutting of rivers. The alternating occurrence of flood periods and dry periods has led to the development of crevasse splays and frequent river channel diversions, resulting in the inability of long-term stable development of the river channel. Besides, the change of water level has also led to the rebuilding of the river. Therefore, the multiple effects led to the formation of an extremely narrow channel shallow water delta. The accuracy of the sedimentary model is verified by a comparative study of the Shaliu River and Buha River in the modern Qinghai Lake. The new extremely narrow channels deposition model proposed this time further improves the deposition theory. At the same time, the modern depositional characteristics of the Shaliu River and Buha River also reveal the reservoir deposition between channels that cannot be distinguished by seismic data, providing guidance for the development of oil and gas in the study area.

Impact of water level change on shifts in subsistence regimes revealed by anthropogenic fire in the lower Yangtze basin during the Mid-Holocene

The lower Yangtze is one of the regions of origin of rice agriculture but it is unclear if environmental change drove the transition from hunting-gathering to agriculture. Long-term and continuous lacustrine records of anthropogenic fire are a more effective means of addressing this problem than the fragmentary terrestrial records available for the lower Yangtze region. We constructed a Holocene fire history revealed by records of black carbon content (BCC) and grain size of the sediments of Lake Nanyi in the lower Yangtze. Our results show the following: 1) Peaks in fire activity occurred during ∼8400–6500 (fire peak P1) and ∼ 1100–0 cal BP (fire peak P2), while weaker fire activity occurred during ∼6500–1100 cal BP (S2). 2) This temporal pattern of fire activity, with a double peak (P1-S2-P2), was asynchronous from east to west across the lower Yangtze. The warm and humid climate would not have caused intense fires and the reduction of forest during ∼8400–6500 and ∼ 1100–0 cal BP. Therefore, we suggest that anthropogenic ignitions, corresponding to pronounced population fluctuations after 8400 cal BP, dominated the regional fire activity. Combined with archaeological evidence, the inverse relationship between the agricultural and population levels and fire intensity during the mid-Holocene suggests that fire intensity at this time was the result of the diversity of landscape types associated with prehistoric subsistence patterns, rather than the magnitude of anthropogenic activity. Combined with sea level, rainfall and archaeological evidence, we propose a mechanism whereby asynchronous water-level rise during ∼8400–6500 cal BP forced the migration of humans to the foothills where they often used fire to modify the landscape as part of a broad-spectrum subsistence pattern. Whereas, water-level fall after 6500 cal BP expanded the area of open ground for human settlement, and in this less diverse landscape, less use was made of fire in agricultural subsistence. Overall, our study reveals how regional water-level, driven by sea-level rise and extreme rainfall, delayed the transition from hunting-gathering to agriculture in the lower Yangtze region.

Design for construction and assessment the accuracy of the automatic monitoring system for the horizontal displacement of the dam of Hoa Binh hydropower plant

The article presents solutions for designing, building and evaluating the accuracy of automatic monitoring system by robotic total station when continuously monitoring horizontal displacement of Hoa Binh Hydropower Plant . The system is designed and built put into operation and used for horizontal displacement monitoring results with high reliability and stability with accuracy of horizontal displacement less than 2.5 mm, for continuous and instantaneous data collection frequency, data can be extracted at any time according the erratic changes of weather, natural disasters or the change of reservoir water level and automatically send an alarm when the horizontal displacement value at the monitoring points reaches the alarm threshold. Continuous horizontal displacement monitoring is the basis to add settlement measurement cycle to check the settlement of the dam when there are abnormal signs of horizontal displacement.

Observing and modelling dynamic changes in temperature and volumetric fluxes within a riverbank aquifer under the influence of seasonal river stage fluctuations

AbstractSeasonal variation causes regular fluctuations in river water levels and water temperatures, which affects the distribution of temperature fields and seepage fields in riparian zones. In this paper, the monitoring device was used to continuously monitor Dongting Lake for a period of 1 year, and the temperature distribution characteristics of the riparian hyporheic zone under seasonal variation were analysed. Ten riparian hydrothermal coupling models based on different soil thermal conductivity models were verified, and the optimal model was used to simulate the influence of the flood process on the temperature field and seepage field of the riparian hyporheic zone. The results show that the changes in groundwater level and temperature in the riparian hyporheic zone had obvious lag and attenuation phenomena compared with the changes in river water level and ambient temperature. The temperature field of the riparian hyporheic zone changed obviously in the year. The vertical temperature gradient was large in summer and winter, the stratification phenomenon was obvious, and the temperature field fluctuation was small. The effect of the flood process on the temperature field and seepage velocity in the riparian hyporheic zone was obviously hysteretic. The effect of the flood‐withdrawing process on the temperature change of the shallow layer was greater than that of the flood‐rising process, while the response of the deep layer temperature change to flood‐rising and flood‐withdrawing processes was the opposite. The effect of floods on the variation in groundwater velocity was that the flood‐rising process was greater than the flood‐withdrawing process.

The fish helminth fauna of Lake Sevan during a period of water level change

Aim. The aim of the work is to study the fish helminth fauna of Lake Sevan basin.Material and Methods. Fish helminths and molluscs were collected from the Lake Sevan basin. A total of 214 specimens of fish were studied. The collection, cameral processing and determination of the material was carried out according to generally accepted methods. Statistical processing of the material was carried out using the BioStat 2009 computer program. 124 specimens of molluscs were examined from the littoral of the Lake Sevan. The collection and identification of molluscs was carried out according to generally accepted methods. The work was carried out at the Scientific Centre of Zoology and Hydroecology of NAS of the Republic of Armenia. Its own collections have been used as material.Results. Trematodes, cestodes, nematodes and acanthocephals were found аs a result of studies of fish from the Lake Sevan basin. The total infestation of the fish by helminths was 27.1 %. Six species of helminths have been identified, two of which are the first to be recorded in new hosts in Armenia. The higher infestations of fish were noted by metacercariae of the trematode Diplostomum sp. and plerocercoids of the cestode Ligula intestinalis. A brief analysis of the infestation of fish by the detected helminths is given.Conclusion. The species composition of the helminth fauna of fish in the Lake Sevan basin was studied. Pathogens of dangerous helminthiases causing the death of fish have been noted. Studies of the helminth fauna of fish in the Lake Sevan basin are relevant and will be continued. Most of the species of fish affected by helminths are of economic importance. Some species of the helminths which were found are very invasive and cause great damage to the fisheries of the republic.

Desain Dermaga Apung Sebagai Sarana Penunjang Kegiatan Ekonomi Nelayan Di Desa Aeng Sareh

The dock is a ship mooring facility to support the sustainability of water transportation (Irwan, 2019). Current developments in many docks use floating docks, where the dock is like a pontoon made of steel or concrete boxes and can float according to changes in water level (Utomo, 2018). Many fishermen in the Sampang Regency area moor at docks made of bamboo on the shoulders of rivers and there are also boats moored around the coast. The condition of the bamboo pier on the river is not very suitable because if the river water recedes it will affect when fishermen are loading and unloading. This problem makes researchers want to make the main object to be able to create design training for young fishermen that is appropriate to the conditions of the river in Aeng Sareh Village, which is often used by fishermen to moor their boats. Researchers offer designs to fishermen in Aeng Sareh Village which will later be used for development.

Differentiating the Effects of Streamflow and Topographic Changes on the Water Level of Dongting Lake, China, Using the LSTM Network and Scenario Analysis

Dongting Lake is the second largest freshwater lake in China and an internationally critical habitat for migratory birds. However, after 2004, the multiyear mean water levels of West Dongting Lake (WDL), South Dongting Lake (SDL), and East Dongting Lake (EDL) in the high-water stage decreased by 1.05 m, 1.15 m, and 1.32 m, respectively. Different areas of Dongting Lake experienced various degrees of shrinkage. It is necessary to study the dominant driving factors and their contributions to the falling water level. In this study, the water level changes in Dongting Lake were analyzed, and a long short-term memory neural network model was constructed to simulate the water level of Dongting Lake. Moreover, the contribution of changes in streamflow and topographic conditions to the water level changes in different areas of Dongting Lake was estimated with scenario analysis. The research results show that the changes in the streamflow were the main driving factors for the water level decline of WDL, SDL, and EDL in the high-water stage, and their contributions were 0.74 m, 0.97 m, and 1.16 m, respectively. The topographic changes had a great falling effect on the water level of Dongting Lake, and the falling effect on the water levels from October to June of the following year was the strongest in EDL (0.81 m), followed by WDL (0.49 m), and the weakest in SDL (0.3 m). These results can provide a scientific reference for the management of the water resources of Dongting Lake.

Monitoring spatiotemporal changes of urban surface water based on satellite imagery and Google Earth Engine platform in Dhaka City from 1990 to 2021

BackgroundThis study focuses on Dhaka City and its impact on urban surface water. Cities, ecosystems, and agriculture need surface water. It is crucial for water resource planning and environmental preservation. The primary aim is to study how urbanization has affected surface water in Dhaka City over 30 years using satellite imagery.MethodsThe study analyzed three decades of urban surface water shifts using Landsat 5 TM and Landsat 8 OLI/TIRS satellite imagery and Google Earth Engine (GEE) with JavaScript code for water ratio index detection. To investigate water level changes, field observation surveys and secondary data analysis were conducted. This integrated methodology simplified surface water data extraction and analysis, making remote sensing easier and allowing cloud-based satellite data processing.ResultsThe study demonstrates that the amount of surface water in cities is going down, from 36.23 km2 in 1990 to 5.83 km2 in 2021, which is an enormous decrease. This means that about 20 square kilometers, or 45 percent of the water's surface, have been lost in the last 30 years. The main reasons for the drop are unplanned expansion of cities, accelerated real estate development, and more trade and economic activities in the study area.ConclusionsThe GEE algorithms provide useful insights into surface water's maximum and minimum extent, enabling appropriate planning and management. These findings aid Dhaka City's water resource management and environmental protection.

Prediction of Storm Surge Water Level Based on Machine Learning Methods

Storm surge disasters result in severe casualties and economic losses. Accurate prediction of storm surge water level is crucial for disaster assessment, early warning, and effective disaster management. Machine learning methods are relatively more efficient and straightforward compared to numerical simulation approaches. However, most of the current research on storm surge water level prediction based on machine learning methods is primarily focused on point predictions. In this study, we explore the feasibility of spatial water level prediction using the ConvLSTM model. We focus on the coastal area of Guangdong Province and employ MIKE21(2019) software to simulate historical typhoons that have made landfall in the region from 1991 to 2018. We construct two datasets: one for direct water level prediction and the other for indirect water level prediction based on water level changes. Utilizing the ConvLSTM network, we employ it to forecast storm surges on both datasets, effectively capturing both temporal and spatial characteristics and thus ensuring the production of dependable results. When directly predicting water levels, we achieve an MAE (mean absolute error) of 0.026 m and an MSE (mean squared error) of 0.0038 m2. In contrast, the indirect prediction approach yields even more promising results, with an MAE of 0.014 m and an MSE of 0.0007 m2. Compared to traditional numerical simulation methods, the ConvLSTM-based approach is simpler, faster, and able to predict water levels accurately without boundary conditions or topographies. Furthermore, we consider worst-case scenarios by predicting the maximum water increase value using the random forest model. Our results indicate that the random forest model can serve as a valuable reference for forecasting the maximum water increase value of typhoon storm surges, supporting effective emergency responses to disasters.

Ecological and photosynthetic characteristics of Carex schmidtii with respect to hydrological fluctuations

Hydrological fluctuations are key abiotic stresses that influence plant growth and photosynthetic processes of wetland plants. However, the response mechanism of the plant characteristics and photosynthesis of Carex schmidtii, with respect to hydrological fluctuations, are still unclear. Comparative studies of plant size parameters, biomass parameters, and photosynthesis parameters of C. schmidtii under the interactive influence of initial water depth (WD), water-level amplitude (WA), and duration time, were performed. The coupling relationship between any two factors of the plant characteristics of C. schmidtii was also examined. Generally, the results showed that the WD and WA treatments, and the duration time, significantly affected plant size, biomass, and photosynthesis of C. schmidtii. The exception was the effect by the WA on the biomass and the NPQ. Furthermore, the biomass and photosynthesis of C. schmidtii were significantly affected by the interactive effects by WD and WA. The plant size, biomass, and photosynthesis parameters of C. schmidtii first increased and then decreased over time. Larger values of plant size, biomass, and photosynthesis parameters (except for qL and NPQ) were found for the treatment with an initial water depth of 0 cm. As was the situation with WD, the largest values of plant height, chlorophyll content, Fv/Fm, and ΔFv/Fm’ were obtained for a water-level amplitude of 0 cm. Furthermore, the chlorophyll content was positively related to the plant size parameters, Fv/Fm, ΔFv/Fm’, and qL. Except for qL, ΔFv/Fm’ had a significant relationship with all plant factors. Lower water levels and smaller water level changes are more conducive to the growth and photosynthese of C. schmidtii. Plant size, biomass accumulation and photosynthesis of C. schmidtii collectively coped with hydrological fluctuations. The findings have improved understanding of the response of C. schmidtii to hydrological fluctuations. They have thereby provided invaluable information for the restoration, management and conservation of tussock wetlands.

Hydrodynamic response to bathymetric changes in Tampa Bay, Florida

Bathymetric changes within estuarine and coastal waters can alter the hydrodynamic evolution of sea level and currents, which in turn can influence the ecosystem by altering material property distributions. Here we apply the Tampa Bay Coastal Ocean Model (TBCOM), with an unstructured, high-resolution grid to investigate the hydrodynamic response to bathymetric changes at the periphery of the Tampa Bay mouth over a relatively small area when compared to the whole model domain. Two separate numerical experiments are conducted with the same forcing, one using the original bathymetry and the other employing a revised synthetic bathymetry. The simulated sea level, amplitude and phase of the M2 tide, and associated currents are compared for the two experiments. Significant changes in water level (up to+/-10 cm) and current velocities (up to 20 cm/s) are found in the shallow peripheral area with the two different bathymetric data sets. These bathymetric influences are not limited to the locations where the bathymetric changes occur; they also extend to remote areas of the bay. Since Tampa Bay bathymetry varies with storm-induced sediment redistributions and human actives such as shipping channel dredging and beach nourishment, these findings emphasize the need for accurate and updated bathymetry for coastal ocean modeling and applications.

Origin and post‐glacial evolution of surface cracks: A case study from the area of the Last Glaciation, north‐eastern Poland

AbstractThe analysis of LiDAR‐based digital elevation models revealed the existence of groups of longitudinal fractures in the ground in northern Poland at the limit of the ice sheet's extent during its last maximum. Our research on the closed elongated depressions (CEDs) of the Jedwabno test field (Szuć site, north‐east Poland) focuses on explaining their origins and their post‐glacial history. This region was covered by an ice sheet and glacitectonically active during the Vistulian, and at least some surface fractures are possible witnesses to this activity. Using geomorphological mapping, sedimentological and geophysical research, we assumed it was related that the origin of these features here is associated with groundwater migration at the end of the Vistulian glaciation or later when groundwater flow intensified due to a rapid climate warming that caused permafrost to melt. The thawing of permafrost caused to transition from continuous permafrost to discontinuous, which in turn created groundwater flow that was probably responsible for the development of the surface cracks (fractures). Radiocarbon, palaeobiological (pollen, Cladocera) and geochemical studies allowed for an estimation of the formation time of these unique surface cracks in the Older Dryas. Prevailing conditions were also reconstructed for the later dynamic changes of the end of the Late Vistulian glaciation and in the Late Holocene until the Subatlantic Period (Megalayan stage). The surface cracks with steep slopes, despite their small area, are extraordinary sedimentation traps that have, in a special way, retained an almost complete record of the environmental and climate changes of the Late Glacial. There are sedimentological gaps in the Holocene, especially after the Preboreal (old part of the Greenlandian Stage), caused by changes in water levels, aeolian processes and human activity.

Satellite Derived Bathymetry and Water Level Change in Beysehir Lake

Abstract Several factors, including water level, depth, water quality, biodiversity, and tourist activities, play a crucial role in the sustainability of lakes, and therefore require constant monitoring. This study aimed to examine the water level changes of Lake Beysehir between 2015 and 2020 and determine whether there was a difference in bathymetry as the lake water level changed. To achieve this, lake water level data was first obtained from Copernicus Global Land Service, which uses satellite altimetry data to determine water level changes in Beysehir Lake. Sentinel-2 multispectral high-resolution satellite images obtained from Sentinel-Hub were then used to determine the depth of the lake. Finally, these high-resolution satellite images were processed using the open-source SNAP software developed by the European Space Agency. A decreasing trend of -9.8 ± 0.8 cm/yr in the lake water level between 2015 and 2020 was revealed by the analysis. The Empirical Satellite-Derived Bathymetry map was produced, and the maximum and average depth of the lake was determined after the required corrections were applied to the Sentinel-2 satellite images. The average depth, which was 8.44 meters in 2015, was found to have decreased to 4.06 meters in 2020. Additionally, a 0.92 correlation was found between the decrease in the lake water level and the average depth change.

Groundwater Level Analysis of Sathyamangalam Region, Tamil Nadu, India Using GIS

The Morphometric and groundwater analysis (water level and flow direction) of Sathyamangalam, having total area of 2.24 lakhs hectares was carried out using geographical information system (GIS). The Watershed characteristics such as slope, size, shape and Morphological Analysis such as linear aspects namely Stream order, Bifurcation ratio, Stream length, Length ratio and Areal aspects in particular Drainage density are analysed using ArcGIS software. And also, groundwater level for four years (2008, 2011, 2014 and 2017) and groundwater flow directions using Piezometric well data were also analyzed. In Watershed characteristics, the size of the study area is 2.24 Lakh ha and designated as sub- catchment watershed. The shape is circular i.e. Fan shape. The total length of contour line is about 11055.86 km and the average slope was 24.68% for 50m interval contour. In Morphological analysis, totally 6487 streams were observed and the total length of stream was 3758.2 km. The study location has bifurcation ratio ranging from 1.56 to 3.62 and length ratio of stream was calculated as 1.678 km/km2. In Piezometric analysis, the major water level changes occur in Northwest of Sathyamangalam. Here, the depth of water from the earth surface decreases from 12.67 m in the year of 2008 to 3.95 m in the year of 2017.

Determination of Replacement Material Thickness in the Case of Expansive Soil in Dams

One simple solution to reduce the impact of damage caused by swelling on expansive soil is to replace it with soil that has better properties. Unlike replacing expansive soil material in the subgrade or foundation layer, replacing expansive material in a constructed dam requires special consideration, as fluctuating reservoir water levels and rainfall cycles affect the active zone of expansive soil, which will affect the stability of the dam. Therefore, this study was conducted to determine the thickness of the replacement layer, which is also the active zone of expansive soil in the dam, by modeling the stability of the dam against changes in reservoir water levels and rainfall cycles with parent analysis using finite element and limit equilibrium method programs. One example of dam damage caused by expansive soil was used as a case study. The study results show that changes in the wet-dry active zone can be used as a basis for determining the thickness of the replacement material in cases of expansive soil in dams.

Geomorphic Response of a Coastal Berm to Storm Surge and the Importance of Sheet Flow Dynamics

AbstractDuring a storm, as the beach profile is impacted by increased wave forcing and rapidly changing water levels, sand berms may help mitigate erosion of the backshore. However, the mechanics of berm morphodynamics have not been fully described. In this study, 26 trials were conducted in a large wave flume to explore the response of a near‐prototype berm to scaled storm conditions. Sensors were used to quantify hydrodynamics, sheet flow dynamics, and berm evolution. Results indicate that berm overtopping and offshore sediment transport were key processes causing berm erosion. During the morphological evolution of the beach profile, two sand bars were formed offshore that attenuated subsequent wave energy. The landward extent of that energy was confined to the seaward foreshore, inhibiting inundation of the backshore. Net offshore‐directed transport was dominant when infragravity motions increased in the swash zone. Conversely, the influence of incident‐band motions on sediment transport was relatively greater in the inner‐surf zone. Near‐bed flow velocities and sheet flow layer thicknesses were larger in the swash zone than in the inner‐surf zone. This paper also provides a valuable analysis between morphology‐estimated total sediment transport rates and rates derived from in situ measurements. Sheet flow dynamics dominated foreshore cross‐shore sediment processes, constituting the largest portion of the total sediment transport load throughout the berm erosion.