High Water Depth Research Articles

Effect of Core Type on Zoned Earth Dams on Total Water Head and Flux

Most dams constructed worldwide are zoned earth dams with cores of different materials. However, selecting the proper core material in an earth dam will reduce seepage and increase safety. Most of the available information on dam cores was extracted from laboratory experiments. In this study, cores of different materials used in three selected zoned dams of almost the same height were assessed based on acquired field data and numerical simulation. The selected dams are in Iraq and named Haditha Dam (designed with a compound core of compacted dolomite and asphaltic diaphragm), Hemrin Dams (designed with a hard clay core) and Khasa Chai Dam (designed with a silty clay core). The total water head and water flux through the core of each dam were simulated using a two-dimensional SEEP/W model. For high and low water depths in the reservoir of Hemrin Dam, the water flux ratios were found to be 140 and 50 times greater than that of Haditha Dam. For low water depth in the reservoirs of Hemrin and Khasa Chai Dams, the flux ratio was 17. Compared with the core of the Hadith Dam, the flux through the core of the Khasa Chai Dam was found to be triple. For studied core samples, the variation in fluxes can be related to the effect of both hydraulic conductivity and geometry of the dam core. The hydraulic conductivity is affected by the core material, while the hydraulic gradient is affected by both the core material and geometry.

Effect of Maximum Seasonal Temperature on Yield and Water Use Efficiency in Forage Corn in Consecutive Growing Seasons

High temperature negatively af fects plant growth and crop yield. The aim was to evaluate the ef fect of maximum temperature on yield and water use ef ficiency in forage corn with subsurface drip irrigation and surface irrigation in five consecutive growing seasons (spring and summer) in the comarca Lagunera. The study was carried out at the La Laguna Experimental Field, of the National Institute of Forestry, Agricultural and Livestock Research (INIFAP) in Matamoros, Coahuila. The research was carried out during summer 2019, spring 2020, summer 2020, spring 2022, and summer 2022 growing seasons. The variables were: maximum temperature, plant height, dry forage, water depth, and water use ef ficiency. The highest temperatures were recorded in spring 2022 and the lowest in the summer growing season of the same year. Overall, the highest plant heights occurred in the coolest growing season (summer 2022). A higher yield of dry forage (19 Mg ha-1) was in the 2022 summer growing season. The highest water depth was applied in the spring 2022 growing season (71 cm) and the lowest in summer 2020 (55 cm). This resulted in higher water use ef ficiency in summer. The variation in water use ef ficiency between growing seasons was due to higher temperatures in spring. Finally, water use ef ficiency tended to decrease by 19% as temperature increased from 30 to 38 degrees Celsius.

Diffusive and ebullitive methane emissions under tidal fluctuation and climate warming in a nutrient-rich subtropical estuary

Estuaries are important sources of methane (CH4) emissions under human activities and global warming. However, diffusive and ebullitive CH4 emissions in response to nutrients enrichments and tidal fluctuations remain largely constrained. Here, we investigated seasonal and monthly CH4 emissions in a nutrient-rich subtropical estuary and evaluated relative contribution of diffusion and ebullition CH4. Dissolved CH4 concentrations were in a range of 0.18–11.2 µmol L−1, corresponding to diffusive fluxes of 3.08–375 μg m−2 h−1 along the estuary. Diffusive CH4 fluxes were observed to decrease significantly from the upper to lower estuary and were higher in the cold than warm seasons. Turbidity, suspended particulate, NH4+, NO3−, DOC/NO3− and NO2− were the crucial factors affecting CH4 fluxes, collectedly explaining 43 % of CH4 emissions variability. Ebullitive and diffusive fluxes were significantly higher under ebbing than flooding tides, with an ebullition contribution of 82–98 %. Ecosystem-level temperature sensitivity and apparent activation energy of CH4 emissions were higher for ebullitive than diffusive pathways and were also higher under the ebbing than flooding tides, indicating that ebullitive pathway is high temperature and low water depth dependent. It is conservatively projected that CH4 emissions would increase by 17 ± 9 % and 40 ± 22 % under the 2 and 4 °C warming scenarios, respectively. These results suggest that enhanced CH4 emissions under human activities and climate warming can be refined in further CH4 projections and highlight the importance of estuaries in global carbon cycles and climate change.

Large variability and 2H-depletion of Middle Miocene to Pleistocene alkenone hydrogen isotopes in the Equatorial Pacific reflect subsurface, low light haptophyte growth

Hydrogen isotope ratios of haptophyte derived long-chain alkenones (δ2HC37:2) have shown to be a useful tool for reconstructing past isotopic compositions of surface seawater (δ2HSSW). The δ2HSSW is related to global ice volume, sea surface salinity and the local hydrological cycle. Here, we present a hydrogen isotope record of alkenones spanning the last 14.5 Ma from IODP site U1338 in the east equatorial Pacific. The alkenone-based reconstructed δ2HSSW is substantially more negative and variable than reconstructed δ2HSSW based on published oxygen isotopes of coccolith carbonates. This suggests that factors other than the isotopic composition of seawater affect the hydrogen isotopic composition of alkenones. The relatively negative and highly variable δ2HC37:2 values are in line with published modern observations on alkenones from suspended particulate matter in the equatorial and north Pacific, with the highest values at relatively high light conditions at the surface and the lowest values at higher water depth and relatively low light conditions. This suggests that the relatively negative and highly variable δ2HC37:2 values in these Middle Miocene to Pleistocene sediments are likely derived from haptophytes growing below the sea surface under variable low light conditions. In regions where the contribution of alkenones from subsurface production, due to high subsurface nutrients, at low light intensities to the sediment is relatively high the δ2HC37:2 has to be interpreted with care as a proxy for δ2HSSW.

UAV-based LiDAR Bathymetry at an Alpine Mountain Lake

Abstract. LiDAR bathymetry provides an efficient and comprehensive way to capture the topography of water bodies in shallow water areas. However, the penetration depth of this measurement method into the water column is limited by the medium water and water turbidity, resulting in a limited detectability of the bottom topography in deeper waters. An increase of the analyzable water depth is possible by the use of extended evaluation methods, in detail full-waveform stacking methods. So far, however, this has only been investigated for water depths of up to 3.50 m due to water turbidity. In this article, the potential of these extended data processing methods is investigated on an alpine mountain lake with low water turbidity and thus high analyzable water depth. Compared to the standard data processing, the penetration depth could be significantly increased by 58%. In addition, methods for depth-resolved water turbidity parameter determination on the basis of LiDAR bathymetry data were successfully tested.

HORA 3D: Personalized Flood Risk Visualization as an Interactive Web Service

AbstractWe propose an interactive web‐based application to inform the general public about personal flood risks. Flooding is the natural hazard affecting most people worldwide. Protection against flooding is not limited to mitigation measures, but also includes communicating its risks to affected individuals to raise awareness and preparedness for its adverse effects. Until now, this is mostly done with static and indiscriminate 2D maps of the water depth. These flood hazard maps can be difficult to interpret and the user has to derive a personal flood risk based on prior knowledge. In addition to the hazard, the flood risk has to consider the exposure of the own house and premises to high water depths and flow velocities as well as the vulnerability of particular parts. Our application is centered around an interactive personalized visualization to raise awareness of these risk factors for an object of interest. We carefully extract and show only the relevant information from large precomputed flood simulation and geospatial data to keep the visualization simple and comprehensible. To achieve this goal, we extend various existing approaches and combine them with new real‐time visualization and interaction techniques in 3D. A new view‐dependent focus+context design guides user attention and supports an intuitive interpretation of the visualization to perform predefined exploration tasks. HORA 3D enables users to individually inform themselves about their flood risks. We evaluated the user experience through a broad online survey with 87 participants of different levels of expertise, who rated the helpfulness of the application with 4.7 out of 5 on average.

Performance analysis and multi-objective optimization of the offshore renewable energy powered integrated energy supply system

Offshore renewable energy technologies offer a promising prospect for energy supply on offshore islands. However, traditional wind and solar energy sources exhibit strong variability and cannot fully meet the energy demands of users. At the same time, the energy demand of users also has great volatility, so the supply side and demand side of energy cannot match well. Existing renewable energy systems often utilize thermal power generation as a stabilizer for the system, however, this approach is difficult to apply in offshore conditions. This study introduces an innovative multi-energy complementary system that integrates seawater freezing desalination, refrigeration and power-hydrogen-ammonia co-generation, driven by ocean thermal energy, wind energy, and solar energy. The system incorporates the use of a new developed small temperature difference ejector refrigeration cycle to stabilize the entire system and produce low-temperature refrigeration. By utilizing the seawater freezing desalination process to minimize energy conversion losses and balancing fluctuations in multiple energy inputs and user demands through ammonia-hydrogen co-production, this approach effectively minimizes energy waste, enhances energy utilization efficiency, and reduces excess power handling. The purpose is to optimize the configuration of the energy conversion subsystem within the multi-energy complementary multi-effect co-generation system, thus improving the economic feasibility and reliability of the system in providing energy and freshwater supply, ultimately achieving the goals of reducing energy waste, achieving high conversion efficiency, and minimizing equipment investment. This study conducts an economic analysis and optimization of a multi-energy complementary system, utilizing a 2 MW-level OTEC subsystem as a stabilizer. Both equipment investment and operating costs are considered in the economy analysis. The carbon emission reduction performance of this system is evaluated. The performance optimization results show that the system achieves an energy storage efficiency of 65.96 %, and the curtailment rate of this system is only 3.99 %, significantly lower than the 10 % curtailment rate in traditional system. The proposed system can meet the annual electricity demand of 33.09 million kWh, as well as a cooling demand of 546.81 million kWh. Under typical conditions, the ocean thermal energy conversion cycle exhibits a power efficiency of 0.85 % and a refrigeration efficiency of 29.10 %. Meanwhile, it annually reduces CO2 emissions by 2.54 million tons, demonstrating significant environmental benefits. This proposed system is mainly applicable to tropical waters with high surface water temperatures and depths of no less than 600 m worldwide. This study offers a practical and economically beneficial solution for energy and freshwater supply on offshore islands.

Typhoon Chan-Hom (2015) induced sediment cross-shore transport in the mud depo-center of the East China Sea inner shelf

The erosion, transport, and deposition processes of sediments that are influenced by typhoons are significant constituents of the sedimentary source-sink processes in marginal seas. Nevertheless, the genesis of storm deposit layers in the continental shelf and their subsequent development and preservation after typhoons have not been comprehensively investigated. In this study, we have conducted a systematic investigation of the processes related to sediment transport and deposition, which were primarily induced by Typhoon Chan-Hom, and analyzed the evolution and preservation of storm deposits utilizing grain-size analysis, radionuclides (137Cs, 210Pbex and 7Be), and organic geochemistry (TOC, TN and δ13C). Sedimentary 137Cs, 210Pbex, and 7Be inventories measured three days after the typhoon suggest that the sediments in the water depth < 30 m were eroded, resuspended, and then transported offshore to deposit in the deeper areas (water depth > 50 m) of the Muddy Deposition Center of Zhejiang-Fujian Coast (MDC-ZFC), resulting in the formation of significant storm deposits (thickness of 8–16 cm) with high 210Pbex and 7Be. In addition to sediment transport, the offshore area also received organic matter generated by typhoon-induced phytoplankton blooms. Hence, in the present study area, the features of marine organic matter that possess high total organic carbon (TOC) content (>0.4%), low carbon to nitrogen (C/N) ratio (<7.5), and high δ13C value (> − 22‰) are crucial for identifying the storm deposit formed by cross-shore sediment transportation. In contrast, the commonly used indicators for identifying typhoon sedimentary records that rely on grain-size coarsening are not suitable for identifying storm deposits at the MDC-ZFC edge due to the influence of relict sands. Furthermore, the radionuclides and organic geochemical signals of the sediments revealed that no significant disturbance or transport of the storm sediments occurred three weeks after the passage of Typhoon Chan-Hom due to the high water depth, indicating that these storm deposits could be effectively preserved in this area. This study provides a valuable basis and reference for accurately identifying and interpreting typhoon sedimentary records in the MDC-ZFC.

Spatial distribution of trace elements and potential contamination sources for surface sediments of the North-Western Black Sea, Romania

It is essential to determine the concentrations of metals/metalloids in marine sediments and their contamination status to develop appropriate pollution control strategies and/or improve existing ones. Spatial distribution of aluminum (Al) and some trace elements, i.e., arsenic (As), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn), accumulated in surface sediments of the north-western (NW) Black Sea (Romanian zone) was evaluated. Sediment samples were collected in 2019 from 32 stations located at water depths in the range of 12.7–149 m. The mean values ± standard deviations (SD) of element concentrations were as follows: 3.9 ± 1.6% for Al, 11.2 ± 10.2 mg/kg for As, 64.8 ± 27.0 mg/kg for Cr, 32.7 ± 15.0 mg/kg for Cu, 0.10 ± 0.09 mg/kg for Hg, 45.3 ± 23.8 mg/kg for Ni, 24.6 ± 9.6 mg/kg for Pb, and 68.0 ± 28.0 mg/kg for Zn. These values are not significantly different (p &amp;gt; 0.05) from those found in a previous study on surface sediments collected in 2018 from 22 stations located in the same area, but at lower water depths (13.5–67 m). Contamination factor (CF) was used to assess the contamination status of surface sediments. The mean values of CF (0.26–1.23) reveal low to moderate contamination with Pb and low contamination with the other elements. Principal component analysis (PCA) and correlation analysis indicated that As, Cu, Ni, Hg, Pb, and Zn were associated with clay, silt, and organic matter, suggesting that these elements mainly came from the Danube discharges and also from local anthropogenic sources, whereas Al, Cr, and partly Hg, Pb, and Zn originated from rock/soil weathering and erosion. The concentration levels of As, Cu, Hg, Ni, Pb, Zn, TOC, silt, and clay were higher in sediments collected from stations generally located at higher water depths (up to 118 m), suggesting that the TEs associated with the finer carriers were transported offshore by currents and waves, whereas the concentration levels of Al, Cr, Hg, and Zn were higher in sediments with lower levels of CaCO3 content (10.1–24.3%), collected from shallower stations (water depths of 12.7–42.0 m).

Consequences of subsea CO2 blowouts in shallow water

Safety and risk assessment of the offshore geological storage of carbon dioxide (CO2) in the Carbon Capture, Utilization, and Storage (CCUS) value chain needs the evaluation of the consequences of possible accidental submarine CO2 leakages, including releases having high flow rate and very long duration, as blowouts. An innovative procedure for the estimation of the effects of submarine blowouts in shallow water was developed, based on the integration of specific sub-models. A model for blowout simulation is used to predict the features of the source term. The fate of the submarine plume is then assessed. Finally, the atmospheric dispersion of the surfacing gas is simulated, to estimate damage distances. The application of the methodology to a set of case studies evidences that in extremely shallow water the threshold distances of the gas cloud dispersing in the air can be higher for CO2 than for natural gas. However, when considering higher water depths, the release of CO2 to the atmosphere is strongly attenuated by the dissolution of CO2 in the water column.

Experimental Study on Axial Stress and Hammer Impacting Energy of Offshore Standard Penetration Test

Standard penetration test (SPT) has been widely used in offshore exploration because of its unique advantages. Unlike onshore exploration, offshore construction areas are characterized by high waves and water depths ranging from several meters to tens of meters. As a result, the reliability of offshore SPT is significantly reduced compared with onshore SPT. Currently, the probe rod length correction of SPT is not involved in geotechnical engineering investigation codes and related research, which greatly limits the application of this method in offshore exploration. Therefore, a series of SPTs were carried out in offshore environments with different water depths, with a maximum rod length of 65 m. The acceleration and axial stress at each test point of the rod were monitored by the dynamic signal data acquisition system, and the hammer impacting energy at each test point was obtained by Force–Velocity (F-V) method. The test results show that the correction of the rod length of the offshore SPT is different from that of the traditional SPT, and it needs to be further corrected for the water depth. In this paper, a modified method of rod length for offshore SPT is proposed, which can provide reference for the application of offshore SPT.

Unveiling the meiobenthic community structure of Prydz Bay, Antarctica during austral summer

Meiobenthos are bottom-dwelling aquatic invertebrates having a size range of 63–500 μm. They play a pivotal role in ecosystem functioning, biogeochemical and trophic nutrient cycling. Due to the presence of Antarctic Circumpolar Current and steep gradient in nutrients and temperature, many taxa of the Southern Ocean (SO) show diverse biodiversity patterns in comparison to other deep sea areas of the world. Over the years, several Indian SO Expeditions have been carried out in the Indian sector of SO (ISSO), but this is a pioneer attempt to unveil the meiobenthic community structure and their functional diversity pattern from Prydz Bay (Indian sector of Southern Ocean), Antarctica. Meiobenthic community structures were investigated in eight different sampling sites along with their vertical profiling from the Prydz Bay during the austral summer 2020. Total meiofaunal abundance ranged from 24 to 521 indv. 10 cm-2, with the highest abundance recorded at station 23 and the lowest at station 9. A total of 9 meiobenthic taxa were found from this eco-region, with the highest percentage being the free-living marine nematodes as metazoan taxa. A total of 86 free-living nematode species were identified, where Sabatieria was the most common genus and represented by eleven species. Several univariate and multivariate analyses deciphered a distinct spatial variation in the meiobenthic community structure. Sediment texture and depth were the most significant environmental variables in shaping nematode assemblages. Biological Trait Analysis was performed using a total of 24 traits in 5 categories to unravel the functional diversity of free-living marine nematodes. The most dominant morphotypes were slender body shape, conical tail shape, dotted cuticle pattern, and non-selective deposit feeders with colonizing abilities of 2 (c–p score 2, in a scale from 1 to 5). Maturity Index (MI) and Index of Trophic Diversity (ITD) were highest in stations 15 and 32, respectively. RLQ approach with fourth-corner analysis was used to decipher the relationship between traits and environmental parameters. The RLQ analysis revealed the positive association of non-selective deposit feeder and slender body-shaped nematodes with higher water depth. The characterization of meiobenthic (especially nematode) communities in the context of taxonomic and functional attributes could help to evaluate the ecological status of ISSO. Further long term monitoring is also needed to get a comprehensive idea about their role in benthic ecosystem functioning in the milieu of global climate change.

How phoD-harboring functional microbial populations trigger the release risk of phosphorus in water sediment system of Shijiuhu Lake, China after experiencing the transseasonal shift

Excessive phosphorus (P) enrichment is the critical cause of eutrophication in the lake water. Organic P (Po) mineralization processes induced by alkaline phosphatase (APase) regulated by phoD-encoding microorganisms in the lake ecosystems was still ambiguous due to the transseasonal shift of water temperatures and depths. Different P pools in the water and sediments of Shijiuhu Lake at varied seasons were measured using chemical extraction methods and solution 31P NMR. The alkaline phosphatase activity (APA) in the sediments were assessed together with enzyme kinetic parameters. The abundances and compositions of microbial communities encoding functional gene phoD were also obtained using high-throughput sequencing. The results showed that Po concentrations remarkably increased from winter toward spring when having higher water depths due to the terrigenous input and biomass deposition. Noteworthy elevation in the PO43- concentration was observed in the interstitial water during the spring, particularly at around 5 cm sediment depth with value reaching as high as 0.43 mg/L. The degradation and mineralization of momoesters and diesters with higher concentrations in the sediments of spring aggravated the PO43- load in the interstitial water. Higher APA reaching 91.6 μg/(g·h) in spring was responsible for the mineralization of Po. Remarkably upwards increasing of absolute abundance of phoD-encoding gene in spring reaching up to 2.6 times of that in winter facilitated the generation of APA in spring. Cobetia and Calothrix followed by Aquabacterium and Mitsuaria were the most abundant phoD-encoding genera with relative abundance > 4%. Weakly positive correlation between dominant bacterial genera and APA and P fractions suggested that low-abundance genera was also involved in the APA generation and Po hydrolysis. These results indicate that spring with high water temperature and depth facilitate the mineralization of Po in the sediment and increase of labile PO43− load in the water, further provide valuable information for the management of eutrophic lakes.

Water and Handwashing in a Drought-Prone Region of Southern Niger: How Environment, Household Infrastructure, and Exposure to Social and Behavior Change Messages Interact.

This study aims to inform multisectoral development programs by exploring the extent to which social and behavior change (SBC) messages, environment, and household infrastructure are associated with knowledge and practice of handwashing behaviors. A cross-sectional survey of 2,708 households in the Maradi and Zinder districts of Niger was collected in April 2021. Household data were integrated with two local environmental measures: 1) water level at the nearest waterhole point, and 2) anomalous rainfall for the previous rainy season derived from climate hazards infrared precipitation with station rainfall (CHIRPS) data. Logistic regression models were constructed to explore how environment, household infrastructure, and exposure to SBC messages were associated with two hygiene-related outcomes: 1) observed water and soap available at household handwashing stations, a behavior, and 2) knowledge of critical moments for handwashing, a behavioral determinant. We find that in households near a water point with higher water depth, households were statistically significantly more likely (odds ratio [OR] = 1.25); (confidence interval [CI] = 1.12-1.49) to have water and soap observed at the handwashing station. Women in households near a water point with increased water depth (more water) were more likely to know three or more critical handwashing moments (OR = 1.07; CI = 1.03-1.11). Exposure to messages about the importance of handwashing was significantly associated with knowledge of critical handwashing moments and having water and soap observed at a handwashing station. Multisectoral programming should consider layering efforts so that development projects that increase access to water sources are complemented with SBC approaches focused on hygiene.

The influence of main channel velocity and water depth changes on the hydrodynamic characteristics of lateral water intake in a tidal channel

Abstract A tidal channel will be affected by the intrusion of seawater, so the current and water depth in the channel will change at every moment. These changes are critical to the hydrodynamic characteristics of water intakes in tidal rivers. This paper establishes a 3D model and validates it through laboratory models, then analyzes the influences of dynamic change of flow velocity and water depth, and the amplitude changes of velocity and water depth on the secondary flow in the water withdrawal process. With the increase of the main flow velocity and the decrease of the water depth, diversion width at the water intake decreases, the peak velocity increases, and the intensity of the secondary flow also increases. With the increase of the velocity of the main channel and the changing rate in water depth, the lag time of the velocity change at the water intake is also longer, and the peak velocity will be greater than the velocity of the constant flow. The influence of the water depth change is greater than that of the main channel velocity change. Combining these four factors, more sand may be washed into the inlet channel under conditions of high flow and low water depth.

Evaluation of a Nature-like Bypass for Non-Salmonids in the Sesan River

In recent years, the hydropower development of the lower Mekong River has accelerated, accompanied by habitat loss and fragmentation. We conducted two experiments using video recordings and traps to evaluate the effectiveness of a nature-like rock ramp bypass in the Sesan River in 2019 and 2021. The results show that the fishway provides both upstream and downstream passage for at least 24 non-salmonid species of fish. The vast majority of fish choose to ascend from July to September, especially in August, and hardly between October and November. The fish inside the fishway prefer to move during the daytime (6:00–18:00), especially during August and September. An excessive water depth at the entrance can lower the number of ascending fish, whereas a higher water depth at the exit can cause the opposite result. Nevertheless, the size of fish monitored exhibits a decreasing trend, suggesting the nature-like bypass cannot completely mitigate the impact caused by this impassable Sesan Ⅱ dam. Therefore, a quantitative assessment of the bypass is highly encouraged, whereas the selection of the tracked fish species and experimental period requires considerable deliberation. This study alleviates the dilemma of insufficient fishway evaluation in tropical countries, which can provide researchers with data support on future non-salmonid fishway designs.

A framework for the sustainable risk assessment of in-river hydraulic structures: A case study of Taiwan’s Daan River

Taiwan has frequently suffered from extreme rainfall in the past decades. A rainfall-induced flood tends to cause the failure of the in-river structure, ecological catastrophe, and even loss of human life and property. This study proposes a risk assessment framework balancing in-river structures’ design strength and ecological impact. The Daan River of Taiwan is examined as a case study to test the proposed framework. First, the study applied persistent scatterer differential Interferometric Synthetic Aperture Radar (PS-InSAR) techniques to analyze the interferometric images captured from the Sentinel-1 satellite to identify large-scale terrain deformation zones of the watershed. A numerical simulation was then applied to assess the impact of different protective in-river structures. Finally, calculations examined the Froude numbers to assess the ecological effects of landscape and fish habitat indicators. In addition, the study applied a wireless monitoring method (i.e., float-out device) to assess riverbed scouring near piers in high-risk regions. The results indicated that the majority habitat type of the stream during base flow is a glide, with an area of about 32%, with run accounting for about 10%. Riffles with high flow velocity and low water depth occupy only about 1%. The primary habitat type during the period of flooding is run with pools near the shore, providing an essential refuge habitat for fish during floods. During the constant current period, exposed sand bars occupy about 55% of the total study area of the river. When a flooding event occurs, the size of the sand bars can be reduced by 40%. Flooding hurts the quality of the habitat of the two fish species considered in this study, with the adverse ecological effects leading to degraded or scattered habitats. The creation of sufficient pool areas on the right bank of the river channel should facilitate the foraging and utilization of fish during regular flow and as a refuge during periods of flooding.

The effect of underwater supplemental light on the growth of V.spinulosa Yan and the restoration process of water

Submerged plants are often used in the ecological restoration of polluted water, and they have good water purifying effect. In the process of water restoration, submerged plants are faced with insufficient light due to high turbidity or water depth. Therefore, we proposed a new model of artificial light assisted submerged plants to purify water nutrients. In this paper, we investigated the effects of locations and light intensities on the growth of V.spinulosa Yan and its water purification effect. The results showed that the light location of the underwater supplemental light was more important than the light intensity. The top supplemental light may provide an excellent environment for algae on the water surface. Excessive algae or epiphytic microorganisms might prevent the V.spinulosa Yan from obtaining light. When the PAR= 109 μmol m−2 s−1, V.spinulosa Yan had a higher biomass (145.39 dw/m2) than before (65.2 dw/m2). When the PAR > 280 μmol m−2 s−1, the clonal reproduction of V.spinulosa Yan was reduced. The main effect of supplemental underwater light on the water restoration process was enhancing the photosynthesis of V.spinulosa Yan by changing ETRmax and Fv/Fm of V.spinulosa Yan leaves. It significantly increased V.spinulosa Yan biomass and improved dissolved oxygen. Improvement of the water environment possibly altered the microbial environment and promoted the removal of water nutrients.

Empirical estimation of the breaker index using a stereo camera system

To understand the wave-breaking phenomenon that affects coastal structures and sediment transport, various experiments have been conducted using an experimental wave flume equipped with point observation instruments including wave gauges. However, it has been still challenging to precisely measure the wave propagation in the breaking region. In this study, the water surface elevation is observed using stereo cameras, and a modified index for the breaking wave height is proposed. Water surface fields are retrieved spatially and temporally from synchronized stereo images using the wave acquisition stereo system (WASS), and then the breaking wave height, location, and wave front slope angle (WFSA) are analyzed. For the verification of the camera system, a three-dimensional reconstructed map is compared with the wave elevation measured by the wave gauge. The critical WFSA is empirically formulated and used to modify the breaker index. We verify the proposed breaker index formula by applying the index to the spilling breakers with a wide range of relative water depths. The prediction of the breaker index that rapidly decreases under high relative water depth conditions is considerably improved. Using the proposed critical WFSA formula and modified breaker index, the breaking wave heights in coastal areas can be accurately estimated.

Growth performance: A comparative analysis of African catfish, Clarias gariepinus fingerlings reared in a cage, concrete pond and earthen pond systems

A comparative study between fingerlings reared in a cage, concrete pond, and earthen pond systems was conducted between March and August 2019. The fish net cage was constructed with ½ netting materials (210 D/9), nylon twine (210 D/9 and 210 D/8), and ropes (10mm PE and 4mm PE, as a house in which the fish fingerlings were stocked. The stocked fish were held captive in the fishnet while water flows through it. This is Treatment 1 (T1). A concrete pond of 10 m x 10 m x 15 m was constructed, as Treatment II (T11). Simultaneously an earthen pond measuring 10m x 10mx 15m was constructed entirely from soil materials both manually and mechanically in a site with excess water retention potential near Otamiri River beside the Fisheries Department of the University of Agriculture. This is Treatment III (T111). Each of the treatments was stocked with 1,500 Clarias gariepinus fingerlings of 10gms average weight and managed simultaneously for the 6 months. Data were analysed by simple descriptive statistics. The result showed 83.3%, 93.3%, and 96.7% survival rates in a cage, concrete pond, and earthen pond systems. Average weight at harvest (gm) and total weight at harvest (gm) of 332.6 gm and 415.7 gm for cage fish farming, 250.6gm and 350.8gm for concrete pond systems, and 250.6 gm and 280.65 gm for earthen pond system. The survival rate in cage culture (83.3%) was low due to high water depth, as the cage was floated; hence fingerlings could not maximize feed intake at the initial stage. The 96.7% suggest that the earthen point system has the highest production rate. Adequate care should be taken to ensure maximal utilization of feed given to the fish in cage floater in water.