Surface Water Depth Research Articles

A high-tech, low-cost, Internet of Things surfboard fin for coastal citizen science, outreach, and education

Coastal populations and hazards are escalating simultaneously, leading to an increased importance of coastal ocean observations. Many well-established observational techniques are expensive, require complex technical training, and offer little to no public engagement. Smartfin, an oceanographic sensor–equipped surfboard fin and citizen science program, was designed to alleviate these issues. Smartfins are typically used by surfers and paddlers in surf zone and nearshore regions where they can help fill gaps between other observational assets. Smartfin user groups can provide data-rich time-series in confined regions. Smartfin comprises temperature, motion, and wet/dry sensing, GPS location, and cellular data transmission capabilities for the near-real-time monitoring of coastal physics and environmental parameters. Smartfin's temperature sensor has an accuracy of 0.05 °C relative to a calibrated Sea-Bird temperature sensor. Data products for quantifying ocean physics from the motion sensor and additional sensors for water quality monitoring are in development. Over 300 Smartfins have been distributed around the world and have been in use for up to five years. The technology has been proven to be a useful scientific research tool in the coastal ocean—especially for observing spatiotemporal variability, validating remotely sensed data, and characterizing surface water depth profiles when combined with other tools—and the project has yielded promising results in terms of formal and informal education and community engagement in coastal health issues with broad international reach. In this article, we describe the technology, the citizen science project design, and the results in terms of natural and social science analyses. We also discuss progress toward our outreach, education, and scientific goals.

Predicting combined tidal and pluvial flood inundation using a machine learning surrogate model

Flooding increases in recent years, in particular for coastal communities facing sea level rise, have brought renewed attention to real-time, street-scale flood forecasting. Such flood models using conventional physics-based modeling approaches are often unrealistic for real-time decision support use cases due to their long model runtime. Machine learning offers an alternative strategy whereby a surrogate model can be trained to mimic relationships present within the physics-based model and, after training, can run in seconds rather than hours. This study used the Random Forest (RF) algorithm to emulate a 1D/2D physics-based model simulating surface water depths in an urban coastal watershed in Norfolk, Virginia. Environmental features from a selected set of pluvial and tidal flood events and topographic information of the roadway were the input variables to train the surrogate model. Results show the potential for the surrogate model to predict flood extent and depth for both pluvial and tidal flood events. Furthermore, the surrogate model can differentiate between flooding locations dominated by pluvial or tidal flooding or impacted by both flooding mechanisms. Flood reports from the mobile app Waze were used for model validation and show 90% agreement with flooding locations from the surrogate model. Finally, feature importance methods were investigated to interpret the performance of the RF models and understand the contribution of different physical features to localized flooding.

Determination of evaporation rate of warm water placed inside a partially-filled top cooled enclosure

Evaporation is an important step in clean water production technologies such as solar desalination. Here, a warm body of impure water evaporates in a differentially heated cavity, the vapour condenses over a cooler surface and the condensate is collected as salt-free water. While buoyancy-driven convection is set-up in air, the water body is subjected to evaporative cooling and buoyancy-driven flow is setup in the water volume as well. Evaporation-induced buoyant flow in water is imaged in the present study using a Mach-Zehnder interferometer in the infinite and wedge fringe settings. The corresponding interfacial heat flux, that includes the contribution from evaporation, is evaluated by analyzing the interferograms. From a modeling perspective, the evaporation rate is the central quantity of importance. It is determined in the present study using an ab initio model for an air-water system that solves mass, momentum, energy, and moisture transport equations with convective flow and jump conditions in the heat flux at the interface. The instantaneous mass and energy fluxes thus determined have also been compared with the kinetic theory model and Dunkle's correlation that is frequently adopted in the design of solar stills. Among the three models, the ab initio approach shows close agreement with experiments. The match with Dunkle's correlation is less satisfactory. The ab initio model closely follows the flow transitions in the air-phase and provides a justification for a good match with the experimentally derived instantaneous evaporative heat and mass fluxes. The ab initio approach is further adopted to parametrically study the effect of initial water temperature, top surface temperature and water depth on the evaporation rate.

Merging Landsat and airborne LiDAR observations for continuous monitoring of floodplain water extent, depth and volume

The Darling River system in Australia is under pressure from water extraction and climate change. Management interventions such as environmental flow releases require understanding of water storage dynamics and the connectivity of floodplains and wetlands. Such knowledge can be gleaned from the long observational record of the Landsat series of satellite sensors and high (<5 m) resolution digital elevation models derived from airborne light detection and ranging (LiDAR). Here, for the first time, we develop and demonstrate an approach to reconstruct 16-day floodplain water dynamics, including extent, depth, and volume for a long Landsat time series (1987 to present). Time series mapping of surface water extent at 5-m resolution was achieved by topographic downscaling of Landsat-derived surface water data. We propose a simple and effective algorithm to restore missing data in the images caused by, e.g., cloud and shadows, swath edges and the Landsat 7 Scan Line Corrector (SLC) failure, thereby increasing the number of useable images five-fold. The 5-m surface water extent maps clearly delineate the narrow river channel and the boundary of floodplain wetlands. They can capture the development, peak and retreat of flood events. By combining Landsat and airborne LiDAR observations, we produced time series of surface water depth mapping at 5-m resolution, accounting for the degree of hydraulic surface water connectivity. Based on these maps, we derived 16-day floodplain volume dynamics for 1987 to present. The correlation coefficient between upstream river flow records and floodplain volume time series was 0.88, indicating that the estimates were robust. The algorithms developed can be used for ongoing very high-resolution mapping to assist in managing human water use and environmental health in the Murray-Darling Basin.

Water level changes in Lake Erie drive 21st century CO2 and CH4 fluxes from a coastal temperate wetland

Wetland water depth influences microbial and plant communities, which can alter the above- and below-ground carbon cycling of a wetland. Wetland water depths are likely to change due to shifting precipitation patterns, which will affect projections of greenhouse gas emissions; however, these effects are rarely incorporated into wetland greenhouse gas models. Seeking to address this gap, we used a mechanistic model, ecosys, to simulate a range of water depth scenarios in a temperate wetland, and analyzed simulated predictions of carbon dioxide (CO2) and methane (CH4) fluxes over the 21st century. We tested our model using eddy covariance measurements of CO2 and CH4 fluxes collected at the Old Woman Creek National Estuarine Research Reserve (OWC) during 2015 and 2016. OWC is a lacustrine, estuarine, freshwater, mineral-soil marsh. An empirical model found that the wetland water depth is highly dependent on the water depth of the nearby Lake Erie. Future wetland surface water depths were modeled based on projection of Lake Erie's water depth using four separate NOAA projections, resulting in four wetland water-depth scenarios. Two of the four 21st century projections for Lake Erie water depths used in this study indicated that the water depth of the wetland would remain nearly steady; however, the other two indicated decreases in the wetland water depth. In our scenario where the wetland dries out, we project the wetland's climatological warming effect will decrease due to smaller CH4 fluxes to the atmosphere and larger CO2 uptake by the wetland. We also found that increased water level can lower emissions by shifting the site towards more open water areas, which have lower CH4 emissions. We found that decreased water depths would cause more widespread colonization of the wetland by macrophyte vegetation. Using an empirical relationship, we also found that further drying could result in other, non-wetland vegetation to emerge, dramatically altering soil carbon cycling. In three of our four projections, we found that in general the magnitude of CO2 and CH4 fluxes steadily increase over the next 100 years in response to higher temperatures. However, in our driest simulations, we projected a different response due to increased oxidation of soil carbon, with CH4 emissions decreasing substantially from an annual cumulative peak of 224.6 to a minimum of 104.7 gC m−2 year−1. In that same simulation, net cumulative flux of CO2 changed from being a sink of 56.5 gC m−2 year−1 to a source of 369.6 gC m−2 year−1 over the same period, despite a temperature increase from 13.7 °C to 14.2 °C. This temperature shift in our other three cases with greater water depths increased the source strength of CH4 and the sink strength of CO2.We conclude that the magnitude of wetland greenhouse-gas fluxes depended on the water depth primarily as it affected the areal percentage of the wetland available for plant colonization, but dramatic decreases in water depths could cause significant reductions in the wetland CH4 fluxes, while simultaneously altering the wetland vegetation.

Spatiotemporal variations of wetland backscatter: The role of water depth and vegetation characteristics in Sentinel-1 dual-polarization SAR observations

Synthetic Aperture Radar (SAR) backscatter observations are sensitive to hydrologic conditions and vegetation characteristics of land cover. This study conducted a high spatial-resolution investigation (30-m) on the response of dual-polarization C-band (5.6 cm wavelength) SAR backscatter coefficients (σ°) to temporal changes of surface water depth (dw) and spatial variations of vegetation characteristics in the south Florida Everglades wetlands. We investigated (1) linear relationships between σ° and dw values, and (2) the effects of vegetation density and morphology on σ°-dw relationships. We developed a new method to classify pixels with significant linear relationships of multi-temporal σ° and dw (R2 > 0.5 and p-value <0.04), which were termed “Reliable Scatterer” (RS). RS included positive, negative, and a combination of both positive and negative relationships (corresponding to RS+, RS−, RS±, respectively). Our analysis revealed spatially varying vegetation densities and morphologies had a significant impact on RS types, where we found RS+ type pixels for woody vegetation, RS± for a mix of medium- and high-density herbaceous vegetation using C-band VV (C-VV) data, and RS− for sparse herbaceous vegetation using C-VH data. Overall, our study indicates that C-band dual-polarization backscatter is sensitive to water-depth variations for some vegetation types, and this sensitivity has the potential to serve as a reliable indicator for monitoring water depth in wetland environments.

Hot, wet and rare: modelling the occupancy dynamics of the narrowly distributed Dixie Valley toad

Context Small population sizes and no possibility of metapopulation rescue put narrowly distributed endemic species under elevated risk of extinction from anthropogenic change. Desert spring wetlands host many endemic species that require aquatic habitat and are isolated by the surrounding xeric terrestrial habitat. Aims We sought to model the occupancy dynamics of the Dixie Valley toad (Anaxyrus williamsi), a recently described species endemic to a small desert spring wetland complex in Nevada, USA. Methods We divided the species’ range into 20 m × 20 m cells and surveyed for Dixie Valley toads at 60 cells during six primary periods from 2018 to 2021, following an occupancy study design. We analysed our survey data by using a multi-state dynamic occupancy model to estimate the probability of adult occurrence, colonisation, site survival, and larval occurrence and the relationship of each to environmental covariates. Key results The detection probabilities of adult and larval toads were affected by survey length and time of day. Adult Dixie Valley toads were widely distributed, with detections in 75% of surveyed cells at some point during the 3-year study, whereas larvae were observed only in 20% of cells during the study. Dixie Valley toad larvae were more likely to occur in cells far from spring heads with a high coverage of surface water, low emergent vegetation cover, and water temperatures between 20°C and 28°C. Adult toads were more likely to occur in cells with a greater coverage of surface water and water depth &gt;10 cm. Cells with more emergent vegetation cover and surface water were more likely to be colonised by adult toads. Conclusions Our results showed that Dixie Valley toads are highly dependent on surface water in both spring and autumn. Adults and larvae require different environmental conditions, with larvae occurring farther from spring heads and in fewer cells. Implications Disturbances to the hydrology of the desert spring wetlands in Dixie Valley could threaten the persistence of this narrowly distributed toad.

Wetland hydropattern and vegetation greenness predict avian populations in Palo Verde, Costa Rica.

Many wetlands around the world that occur at the base of watersheds are under threat from land-use change, hydrological alteration, nutrient pollution, and invasive species. A relevant measure of whether the ecological character of these ecosystems has changed is the species diversity of wetland-dependent waterbirds, especially those of conservation value. Here, we evaluate the potential mechanisms controlling variability over time and space in avian species diversity of the wetlands in the Palo Verde National Park, a Ramsar Site of international importance in Costa Rica. To do so, we assessed the relative importance of several key wetland condition metrics (i.e., surface water depth, wetland extent, and vegetation greenness), and temporal fluctuations in these metrics, in predicting the abundance of five waterbirds of high conservation value as well as overall waterbird diversity over a 9-yr period. Generalized additive models revealed that mean NDVI, an indicator of vegetation greenness, combined with a metric used to evaluate temporal fluctuations in the wetland extent best predicted four of the five waterbird species of high conservation value as well as overall waterbird species richness and diversity. Black-bellied Whistling-ducks, which account for over one-half of all waterbird individuals, and all waterbird species together were better predicted by including surface water depth along with wetland extent and its fluctuations. Our calibrated species distribution model confidently quantified monthly averages of the predicted total waterbird abundances in seven of the 10 sub-wetlands making up the Ramsar Site and confirmed that the biophysical diversity of this entire wetland system is important to supporting waterbird populations both as a seasonal refuge and more permanently. This work further suggests that optimizing the timing and location of ongoing efforts to reduce invasive vegetation cover may be key to avian conservation by increasing waterbird habitat.

Fishing Ground Mapping of Demersal Fish in The Riau Islands Province Waters Related to the Oceanographic Factors

Research on the potential fishing ground for demersal fishing is a way to determine the areas that have the potential for fishing activities. Potential fishing ground mapping can be done by observing the dynamics of oceanographic parameters. The use of satellite imagery helps in providing oceanographic data in order to study the variability of oceanographic parameter. The aim of the study was to analyse the relationship between oceanographic parameter and demersal fish catch in order to validate potential fishing grounds for demersal fish. This research has been conducted in the waters of the Riau islands. Field observations and data collection including surveys of fishing grounds and identification of fish catches were carried out during March to August 2020. To support the analysis, Aqua-Modis Level-3 satellite data was used to observe the oceanographic variations. The data used in the analysis consisted of fishing grounds coordinate information, catches, sea surface temperature, chlorophyll-a, water depth, and salinity. The results showed that during the period 2010-2020, oceanographic dynamics did not experience significant changes or tended to be stable. Most of the research areas indicated appropriate categories for fishing activities based on the research parameters analysis. The correlation of the research parameters described a significant effect on fishing activities.

Species Composition, Abundance and Diversity of Phytoplankton Inhabiting around the Swatch-of-No-Ground of Northern Bay of Bengal

This study aimed to estimate the abundance and diversity of phytoplankton at different depth of water columns in Northern Bay of Bengal, Bangladesh. Samples were collected from 24 stations using Niskin water sampler from 0 to 250 m depths in four different cruises from January, 2017 to January, 2018 with the collaboration of Bangladesh Navy. Before sample identification, the samples were subjected to preservation using Lugol’s solution. A total of 70 phytoplankton species were identified of which Bacillariophyceae, Dinophyceae and Chlorophyceae covered 74.28%, 21.42% and 4.28% of species, respectively. The average phytoplankton density was 12,238±7,281 cells/L. Results showed phytoplankton abundance and distribution was comparatively lower in higher water depth than surface water. The highest phytoplankton abundance (39,342 cells/L) was recorded at surface water and the lowest abundance (16 cells/L) was observed in 200 m depth. Phytoplankton abundances significantly reduced at higher water depths (p &lt; 0.05) which might be associated with higher light and nutrients availability at surface water and mixed layer depth. However, there was weak negative correlation since r = - 0.33. Phytoplankton abundance was also varied from station to station at similar water depth. Species richness was the highest in surface water. In this study, estimated Shannon-Wiener index was 0.58 that represented phytoplankton was moderately distributed at surface water than higher depth. The findings of the present study might be used as a baseline study to understand the phytoplankton community of the Northern Bay of Bengal which directly and/or indirectly help to manage existing ecosystem and sustainable fisheries of the Bay of Bengal. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 10(1), 2021, P 11-21

Effect of Surface Water Level Fluctuations on the Performance of Near-Bank Managed Aquifer Recharge from Injection Wells

Managed aquifer recharge operations are often conducted in near-bank areas to regulate water resources or reduce seawater intrusion. Yet little is known about the influence of surface water level fluctuations at different temporal scales on MAR performance. A generalized conceptual model was developed based on an investigation site in Western China as a basis to simulate the response surface water level fluctuations on the water table, artificially recharged water lens (formed by the artificially recharged water), groundwater flow paths and average travel times (which is an important control on how quickly contaminants are flushed out of aquifers), and the discharge of the artificially recharged aquifer during the surface water level fluctuation. The results showed a fluctuating groundwater table in the artificially recharged near-bank aquifer under the influence of surface water level fluctuations. The peak values of the increment of the groundwater table induced by artificial recharge decreased with the increase of the period and amplitude of surface water level fluctuation, but the trough values of the increment of water table increases with that. The penetration depth of surface water into the aquifer with a fluctuating surface water level leads to a decreasing increment of the groundwater table which follows a power law. The fluctuating surface water level leads to dynamic changes of artificially recharged water lens morphology and a thinner artificially recharged water lens. A mixing zone of recharged water and ambient water could be found in the artificially recharged near-bank area, which is expected to lead to modifications in the geochemical conditions in the artificially recharged near-bank aquifer. A longer period of surface water level fluctuation leads to a longer average travel time, but the larger penetration depth of surface water and amplitude lead to a shorter average travel time. The peak discharge of the near-bank aquifer was found to decrease with the period of surface water level fluctuation, but it increases with penetration depth and amplitude. This study is important in providing insights into the performance of near-bank managed aquifer recharge with respect to surface water level fluctuation.

Estimating anthropogenic effects on a highly-controlled basin with an integrated surface-subsurface model

This study presents a decision support method that can quantify the effects of water management practices on surface water and groundwater systems using a basin-scale fully-integrated model. For improvement to the decision-making process, the integrated model consists of evapotranspiration, surface, and subsurface hydrologic conditions and accounts for anthropogenic water management such as groundwater pumping, and dam and weir operations, which significantly affect the water resources of the Geum River Basin, South Korea. In this study, the fully-integrated model is calibrated based on a step-wise calibration approach. For a reliable decision support model, the calibrated model was further evaluated against five-year monthly transient agricultural pumping and control structure operation data with taking into account the parametric uncertainty of the model. The calibration and evaluation results agree well with various observation datasets including watertable depths, surface flow, reservoir water depths, and dam and weir discharge rates. Simulation results reveal that annual average net precipitation ratio for the simulation period is 0.32 with a range from 0.12 to 0.40, which is a water surplus condition. Within each year, however, negative net precipitation ratios, or water deficit conditions, occur consistently during the dry seasons, indicating that the hydrologic systems in the basin may be vulnerable during the dry seasons. Groundwater pumping within the basin lowers the local groundwater levels an average of 0.52 m over five years. In the downstream area of the basin, groundwater pumping activities affect approximately 30% of the area and result in a reduction of groundwater levels by 0.4 m with an acceptable range of uncertainty. As a decision support method for weir operations, we apply a weir removal scenario to evaluate the changes in surface flow conditions. The simulation results reveal that surface flow rates in weir reservoirs increase by three orders of magnitudes and surface water depths in the reservoirs of the dams and weirs reduce by two to four times compared to a case where all the weirs are in operation. Therefore, appropriate weir removal plans are necessary to minimize the impact on the ecosystem of the Geum River.

The redox fate of hydrogen peroxide in the marine water column

AbstractMarine microbes produce extracellular reactive oxygen species (ROS) such as superoxide and hydrogen peroxide (H2O2) as a result of regulated and nonregulated physiological and metabolic reactions. ROS production can be a sink and cryptic recycling flux of dissolved oxygen that may rival other key fluxes in the global oxygen cycle; however, the low abundance and high turnover rate of ROS makes this figure difficult to constrain. One key step in determining the disparity between the gross production of ROS and the net sink of dissolved oxygen lies in understanding the degradation pathways of H2O2 in the marine water column. In this study, we use isotope‐labeling techniques to determine the redox fate of H2O2 in a range of marine environments off the West Coast of California. We find that H2O2 reduction is greater than or equal to H2O2 oxidation at most sampled depths, with notable exceptions in some surface and intermediate water depths. The observation that H2O2 oxidation can exceed reduction in the dark ocean indicates the presence of an oxidizing decay pathway that is not among the known suite of microbially mediated enzymatic pathways (i.e., catalase and peroxidase), pointing to an abiotic and/or a nonenzymatic decay pathway at intermediate water depths. These results highlight the complexity and heterogeneity of ROS decay pathways in natural waters and their unconstrained regulation of oxygen levels within the ocean.

2D-HEC-RAS Modeling of Flood Wave Propagation in a Semi-Arid Area Due to Dam Overtopping Failure

Dam overtopping failure and the resulting floods are hazardous events that highly impact the inundated areas and are less predictable. The simulation of the dam breach failure and the flood wave propagation is necessary for assessing flood hazards to provide precautions. In the present study, a two-dimensional HEC-RAS model was used to simulate the flood wave resulting from the hypothetical failure of Al-Udhaim Dam on Al-Udhaim River, Iraq, and the propagation of the resulting dam-break wave along 100 km downstream the dam site for the overtopping scenario. The main objective is to analyze the propagation of the flood wave so that the failure risk on dam downstream areas can be assessed and emergency plans may be provided. The methodology consisted of two sub-models: the first is the dam breach failure model for deriving the breach hydrograph, and the second is the hydrodynamic model for propagating the flood wave downstream of the dam. The breach hydrograph is used as an upstream boundary condition to derive the flood impact in the downstream reach of Al- Udhaim River. The flood inundation maps were visualized in RAS-Mapper in terms of water surface elevation, water depth, flow velocity, and flood arrival time. The maximum recorded values were: 105 m (a.m.s.l.), 18 m, 5.5 m/s, and, respectively. The flow velocity decreased from upstream to downstream of the terrain, which means less risk of erosion in the far reaches downstream of the study area. The inundation maps indicated that the water depth and flow velocity were categorized as Catastrophic limits on the terrain's area. The results offer a way to predict flood extent and showed that the impact of a potential dam break at Al-Udhiam Dam will be serious, therefore, suitable management is needed to overcome this risk. Moreover, the maps produced by this study are useful for developing plans for sustainable flood management. Doi: 10.28991/cej-2021-03091739 Full Text: PDF

Taxonomic and functional macroinvertebrate diversity of high‐altitude ponds in the Macun Cirque, Switzerland

Abstract Global environmental change is threatening freshwater biodiversity with ecological impacts predicted to be particularly severe in high‐altitude regions. Despite this, an ecological understanding of high‐altitude pond networks remains patchy, with only limited knowledge of the environmental and spatial predictors of taxonomic and functional diversity. Moreover, previous studies of pond ecosystems have focused primarily on taxonomic richness and largely overlooked functional diversity. This study examined the influence of local environmental and spatial factors on taxonomic and functional α and β diversity (including the turnover and nestedness‐resultant components) of 17 high‐altitude (~2,500 m above sea level) pond macroinvertebrate communities, in the Macun Cirque, Switzerland. Spatial processes (pond connectivity) were important drivers for taxonomic α diversity, while local environmental variables (pond permanence and surface area) were important determinants of functional α diversity. Species turnover was the most important component of β diversity for taxonomic composition, and functional composition demonstrated a nested spatial pattern. Variation in taxonomic and functional composition (and the turnover and nestedness components of β diversity) were determined by local environmental variables despite the limited environmental gradients within the pond network. No significant effects of spatial variables on community composition were recorded for either facet of diversity, indicating that compositional variation was determined at a local scale. Water temperature, depth and pond permanence were consistently the most important measured drivers of diversity. Given the importance of both spatial and environmental variables in structuring taxonomic and functional diversity, landscape‐scale conservation and management activities that aim to improve or protect high‐altitude freshwater biodiversity should focus on maintaining connectivity among ponds and environmental heterogeneity, particularly pond surface area, water depth, and hydroperiod. Understanding the mechanisms driving taxonomic and functional diversity will be critically important for the management and conservation of macroinvertebrate communities in high‐altitude pond networks in the face of climatic warming.

Novel Method for the Estimation of Vertical Temperature Profiles Using a Coastal Acoustic Tomography System

Systems based on remote sensing technology, which use reciprocal acoustic signals to continuously monitor changes in the coastal oceanic environment, are referred to as coastal acoustic tomography (CAT) systems. These systems have been applied in regions in which heavy ship traffics, fishing and marine aquaculture activities make it difficult to establish in situ oceanic sensor moorings. Conventionally, CAT measurements were used to successfully produce horizontal maps of the depth-averaged current velocity and temperature in these coastal regions without attempting to produce a vertical temperature profile. This prompted us to propose a new method for vertical temperature profile estimation (VTPE) from CAT data using the available sea surface temperature (SST), near-bottom temperature (NBT), and water depth. The VTPE method was validated using data-assimilated and tide-included high-resolution ocean model outputs, including tide data, by comparing the estimated and simulated temperatures. Measurements were performed in the southern coastal region of Korea, where two CAT stations were moored to establish a continuous coastal ocean monitoring system. The validation results revealed that the algorithm performed well across all seasons. Sensitivity tests of the VTPE method with reasonable realistic random errors in the SST, NBT, and acoustic travel time measurements demonstrate that the method is applicable to CAT observation data because the monthly mean root-mean-squared difference (RMSD) for the vertical profiles for February, May, August, and November were 0.23, 0.30, 0.50, and 0.24°C, respectively. The VTPE method was applied to the CAT observation datasets acquired in February and August. The transceivers at the CAT stations were at depths 11 and 6 m on average. The RMSD between the estimated and observed temperatures in the middle layer (∼3 m depth) between two stations in February and August were 0.08 and 0.60°C, respectively, the accuracy of which is sufficient in largely time-varying coastal environments. We provide a novel method for continuous coastal subsurface environmental monitoring without interrupting maritime traffic, fishing, and marine aquaculture activities.

Investigation of Scale-Dependent Groundwater/Surface-water Exchange in Rivers by Gradient Self-Potential Logging: Numerical Modeling and Field Experiments

Exchanges of groundwater and surface-water are fundamental to a wide range of water-supply and water-quality management issues but challenging to map beyond the reach scale. Waterborne gradient self-potential (SP) measurements are directly sensitive to water flow through riverbed sediments and can be used to infer exchange locations, direction (gain versus loss), scale, and relative changes, but to date applications to river corridor hydrology are limited. Numerical modeling and field experiments were therefore performed herein, each emphasizing waterborne gradient SP logging for identifying and locating focused vertical groundwater discharge (surface-water gain) and recharge (surface-water loss) in a river. Two and three-dimensional numerical models were constructed to simulate the polarities, appearances, and peak amplitudes of streaming-potential and electric-field anomalies on a riverbed and in the surface-water that were attributable to steady-state vertical fluxes of groundwater through high-permeability conduits in the riverbed. Effects of varied hydraulic length-scale of exchange and surface-water depth were tested through numerical modeling. Modeling results aided in data acquisition and interpretation for three repeated field experiments performed along a 1.5–2.0 km reach of the Quashnet River in Cape Cod, Massachusetts, where focused, meter-scale groundwater discharges occur at discrete locations within otherwise ubiquitous and more diffuse groundwater upwelling conditions. Strong gradient SP anomalies were repeatedly measured in the Quashnet River at previously confirmed locations of focused groundwater discharge, showing the efficacy of waterborne gradient SP logging in identifying and characterizing groundwater/surface water exchange dynamics at multiple river network scales.

A missing link in the mid‐late Permian record of north‐eastern Pangea: A sedimentological evaluation of the Permian Belfast Harbour Evaporite Formation of County Antrim, Northern Ireland

AbstractAncient salt deposits preserve a record of highly specific environmental, climatic and biological conditions, including past surface water chemistry and water depths, local air temperatures, atmospheric composition and halophilic microorganisms. This paper presents the first sedimentological study of the mid‐Late Permian Belfast Harbour Evaporite Formation of Northern Ireland. This formation is dominated by bedded halite, contains some siliciclastic mudstone and bedded anhydrite, and is cross‐cut by intrusive igneous rocks. The bedded halite lithology contains bottom‐growth chevron and cornet crystals, efflorescent crusts and dissolution pipes, which are evidence of a saline surface brine that underwent periods of evapoconcentration, desiccation and flooding. The mudstone lithology contains dewatering structures, intraclasts and mudcracks, which indicate flooding and desiccation in dry mudflats. Bedded anhydrite was deposited as beds of gypsum cumulate crystals in saline surface waters. The Belfast Harbour Evaporite Formation was formed by saline lakes with associated mudflats, based on sedimentary characteristics and supported by mineralogical, geochemical and stratigraphic context. Diagenetic features reflect dissolution and cementation at the surface and shallow subsurface in the depositional environment and limited late‐stage alterations. Syndepositional dissolution pipes in bedded halite were formed by flooding events. Early halite cement is present in dissolution pipes and mudstones. Gypsum/anhydrite repeatedly dehydrated and rehydrated to form an interlocking crystal mosaic. Later features include fluid migration and the intrusion of mafic rocks. The Belfast Harbour Evaporite Formation was deposited by an ephemeral saline lake and dry mudflat system in an arid climate. This study, when compared to age‐equivalent continental deposits elsewhere, suggests that arid settings with saline lakes existed across much of Pangea during the Permo‐Triassic. The Belfast Harbour Evaporite Formation stratigraphically underlies the extremely low pH saline lakes of the Mercia Mudstone Group, implying that it aids in understanding the formation of Pangean acid brine lakes.

Characteristics of lacustrine deepwater fine-grained lithofacies and source-reservoir combination of tight oil in the triassic chang 7 member in Ordos Basin, China

The lithofacies characteristics of fine sedimentary rocks affect the hydrocarbon generation capacity and reservoir performance of tight oil and are closely related to the sedimentary environment. On the basis of field outcrops and core observations, combined with logging data, thin section identification, grain size analysis, organic carbon analysis and physical property tests, the fine sedimentary facies of the Chang 7 Member in the Ordos Basin are studied. Nine lithofacies types are identified in the study area, including planar and trough cross-bedding sandstone facies (Spt), massive bedding sandstone facies (Sm), slump deformation fine sandstone facies (Ssd), sand-mud interbedded facies (Sb), rippled siltstones facies (Fr), horizontal bedding mudstone facies (Mh), massive bedding mudstone facies (Mm), horizontal bedding shale facies (S) and tuff facies (T). Lithofacies types Spt, Ssd, Fr are developed in the gentle slope belt in the northeastern study area, which is a delta front-semi-deep lake sedimentary environment and mainly contains underwater distributary channel and estuary dam sedimentary microfacies types. Lithofacies types such as Sm, Sb, Mh and T are developed in the southwestern steep slope zone of the study area, which is a channel-type gravity flow sedimentary environment, and sedimentary microfacies types such as near-source channels, far-source channels and leading-edge dolomites are developed. In the vertical direction, during the Chang 73 sedimentation period, the lake surface area and water depth reached their maxima, and S and Mh lithofacies developed, which were conducive to the formation of high-quality hydrocarbon source rocks for tight oil. During the Chang 72-Chang 71 sedimentation period, the lake basin shrank, and the reducibility of the water body weakened. The delta front sand body composed of Spt lithofacies in the northeast and the sandy clastic flow sand body composed of Sm in the southwest constitute the main tight oil reservoirs. High-quality hydrocarbon-generating lithofacies and favourable reservoir lithofacies are spatially superposed and developed, forming two source-reservoir combinations in the Chang 7 tight oil source-reservoir formation and near source-reservoir formation.

Optimizing the working performance of a boat-type tractor using central composite rotatable design and response surface method

Optimization of the structural and working parameters for a boat-type tractor is essential to improve the working performance and reduce the energy consumption of the agricultural machinery. To apply the central composite rotatable design and response surface method, the individual and interactive impacts of grounding pressure (X1), sliding speed (X2), depth of surface water (X3), curvature radius of the bow (X4), and grounding angle (X5) on the sliding resistance and subsidence depth of a self-designed boat-type tractor were assessed. An analysis of variance test indicated that the sliding resistance and subsidence depth were significantly sensitive to all independent variables except X4, and the contribution rates of a single factor on the sliding resistance and subsidence depth were ordered as X1 > X5 > X2 > X3 > X4. The terms X4X5 and X1X5 were the only significant factors (p < 0.05) that affected the sliding resistance and subsidence depth, respectively. Subsequently, the optimal combination of the structural and working parameters for the boat-type tractor on a specific soil was determined. The results suggested that the minimal sliding resistance was 150.71 N, which was obtained when X1, X2, X3, X4, and X5 were 265.2 kg m2, 0.52 m s−1, 2.35 cm, 454.01 mm, and 28.88°, respectively. To verify the working performance of the boat-type tractor with the optimized parameters, laboratory tests were performed on the hull model in soil bins. Using the original working parameters, the sliding resistance and subsidence depth were 165.2 N and 7.1 cm, respectively, which were accordingly optimized to 159.8 N and 6.7 cm with the optimal parameters. Consequently, the sliding resistance was reduced by 5.4 N (3.3%), and the subsidence depth was decreased by 0.4 cm (5.6%), indicating that the working performance of the boat-type tractor was greatly improved.