Pond Depth Research Articles

Impacts of land use/cover change on urban rainfall-flooding processes based on numerical simulations

The evolution of surface conditions caused by urbanization has a great impact on urban flooding, whose increasing frequency of occurrence has severely affected urban safety. Most previous studies have focused on land use/cover change (LUCC) but haven’t specifically explored the effects of LUCC on the spatial distribution of flood points and the ponded depth. We combined the storm water management model (SWMM) with multi-year remote sensing data to simulate the flood points and ponded depth in different rainstorm types. Results showed that the ratios of flood points with ponded depths > 0.7 m increased from 2.58% to 17.12%, with the evolution of the urban surface conditions in 1988-2021. And the flood points with ponded depths > 0.7 m were mainly located in the southern and northwestern parts of Bantian Street. These results can provide better-informed decision making for storm water management and early warning of flooding disasters in Shenzhen.

Alluvial floodplain gully erosion in dryland rivers – An overlooked source of sediment with implications for river condition and management

Dryland alluvial rivers are naturally complex systems with a range of in-stream and floodplain geomorphic units that provide habitat for aquatic and terrestrial biota. These systems are increasingly threatened by accelerated rates of sedimentation leading to declines in geomorphic complexity, habitat quality, and ponding depth. The implications of sedimentation on waterholes, or deep pools, is of particular concern, as they provide critical refugia in arid environments. However, sources of sediment entering and infilling waterholes, and the flow-on effects for habitat and water quality, are not well understood. This study addresses the potential for sediment derived from alluvial floodplain gullies to influence geomorphic change in dryland rivers. Alluvial floodplain gullies are often overlooked in comparison to more widely documented hillslope, or colluvial, gullies. Alluvial gullying is a prevalent feature of the Barwon-Darling River, one of Australia's longest and most important waterways in the northern Murray-Darling Basin (MDB). The estimated volume of sediment derived from floodplain gullies is 168 million m3, which far exceeds estimates used in past sediment budgets. Gully size and complexity varied from small, linear features to large, complex, branching gullies and the total number of gullies increased by ~40 % from the 1960s to 2000s. However, the more recent episodes of gullying (i.e., post 1960s) are limited to smaller gullies, which are likely to yield less sediment than the side walls of the older, larger, more complex gullies. Based on the average decline in maximum waterhole depth, ~19 million m3 of sediment has accumulated in Barwon-Darling waterholes over the past 120 years (equivalent to ~158,000 m3 a−1). A predictive relationship between gully volume and change in waterhole depth was expected, but not observed. Nevertheless, the role of alluvial floodplain gullies as a significant source of sediment should not be overlooked when assessing dryland river forms and processes. River management should consider the implications of changing sediment sources and in-stream loads, with associated changes in water quality and aquatic habitats, which influence river condition.

Experimental and numerical study of cadmium fate and transport mechanisms during artificial recharge in agricultural regions

Agricultural Managed Aquifer Recharge (AgMAR) uses agricultural lands and floodwater to enhance groundwater recharge, but its effectiveness can be hindered by heavy metals like cadmium (Cd), which pose risks to groundwater quality. Cd is particularly concerning due to its high mobility and persistence in the environment. This study investigates Cd's fate and transport in agricultural regions during MAR, focusing on sandy loam soils through batch and column experiments. Equilibrium and kinetic batch studies were conducted under varying Cd concentrations and exposure times to quantify the adsorption capacity and rate. HYDRUS-2D was used to simulate Cd's transport in soil under various ponding depths and Cd concentrations. Results showed a maximum Cd adsorption capacity of 439.58 mg/kg, with the Freundlich isotherm providing a better fit (R2 = 0.98) and indicating heterogeneous adsorption sites (n = 0.389). The kinetic experiment indicated chemisorption as the predominant mechanism, with an equilibrium adsorption capacity of 236.49 mg/kg. The pseudo-second-order kinetic model (rate constant 0.0016 h⁻1, R2 = 0.99) suggested that adsorption kinetics are influenced by Cd concentration and available adsorption sites. The column experimental findings supported by HYDRUS-2D modeling successfully explained the fate and transport of Cd within the soil columns. The model fitted parameter values for Freundlich adsorption isotherm coefficient (KF), linearity factor (Nu), and kinetic rate coefficient are (α) 47.37 L/kg, 0.00389 cm³/ppm and 0.0029 min⁻1, respectively. Modeling scenarios further elucidated the transport dynamics of Cd under simulated AgMAR conditions. Modeling scenarios indicated that with constant ponding of 5 cm over a year, Cd at 20 and 40 ppb concentrations in floodwater could potentially migrate below root zone systems. This study highlights the critical role of understanding Cd fate and transport in optimizing AgMAR systems and reducing Cd pollution risks, providing valuable insights for developing effective monitoring and management strategies.

Improving light availability and creating high-frequency light–dark cycles in raceway ponds through vortex-induced vibrations for microalgae cultivation: a fluid dynamic study

Limited light availability due to insufficient vertical mixing strongly reduces the applicability of raceway ponds (RWPs). To overcome this and create light–dark (L/D) cycles for enhanced biomass production through improved vertical mixing, vortex-induced vibration (VIV) system was implemented by the authors in a previous study to an existing pilot-scale RWP. In this study, experimental characterization of fluid dynamics for VIV-implemented RWP is carried out. Particle image velocimetry (PIV) technique is applied to visualize the flow. The extents of the vertical mixing due to VIV and the characteristics of L/D cycles were examined by tracking selected particles. Pond depth was hypothetically divided into three zones, namely dark, light Iimited and light saturated for detailed analysis of cell trajectories. It has been observed that VIV cylinder oscillation can efficiently facilitate the transfer of cells from light-limited to light-saturated zones. Among the cells that were tracked, 44% initially at dark zone entered the light-limited zone and 100% of initially at light-limited zone entered the light-saturated zone. 33% of all tracked cells experienced high-frequency L/D cycles with an average frequency of 35.69 s−1 and 0.49 light fraction. The impact of VIV was not discernible in the deeper sections of the pond, due to constrained oscillation amplitudes. Our findings suggest that the approximately 20% increase in biomass production reported in our previous study can be attributed to the synergistic effects of enhanced L/D cycle frequencies and improved light availability resulting from the transfer of cells from dark to light-limited zones. To further enhance the effectiveness of VIV, design improvements were developed. It was concluded that light availability could be significantly improved with the presented method for more effective use of RWPs.

Simulation of Flow and Salinity in a Large Seasonally Managed Wetland Complex

Seasonally managed wetlands in the San Joaquin River (SJR) watershed in California provide important benefits to wildlife and humans but are threatened through anthropogenic activity. Wetlands in the SJR are subject to salinity regulation, which poses challenges for wetland management. Salinity management in the SJR basin is supported by a process-based model, the Watershed Analysis Risk Management Framework (WARMF). Wetlands are simulated with a “bathtub” analog where water levels are assumed to be the same over one model compartment and the storage volume depends on depth. The complexity and extent of hydrological features pose challenges for input data acquisition. Two approaches to estimating inflow and pond depth and determining water sources were assessed. Approach 1 used mostly monitored data, while Approach 2 used wetland manager knowledge. Approach 2 predicted outflow and salinity better than Approach 1, and an important benefit was the simulation of water reuse within the wetland complex, which was previously not implemented. Approach 1 is generally suited for estimating pond depth when a model compartment represents one wetland, while Approach 2 is suited for wetlands with large spatial extent, many hydrological features, and managed flows. The improved model will support wetland management.

Evolution of Secondary Periglacial Environment Induced by Thawing Permafrost near China–Russia Crude Oil Pipeline Based on Airborne LiDAR, Geophysics, and Field Observation

The China–Russia crude oil pipeline (CRCOP) operates at a temperature that continuously thaws the surrounding permafrost, leading to secondary periglacial phenomena along the route. However, the evolution and formation mechanisms of these phenomena are still largely unknown. We used multi-temporal airborne light detection and ranging (LiDAR), geophysical, and field observation data to quantify the scale of ponding and icing, capture their dynamic development process, and reveal their development mechanisms. The results show that the average depth of ponding within 5 m on both sides of the pipeline was about 31 cm. The volumes of three icings (A–C) above the pipeline were 133 m3, 440 m3, and 186 m3, respectively. Icing development can be divided into six stages: pipe trench settlement, water accumulation in the pipe trench, ponding pressure caused by water surface freezing, the formation of ice cracks, water overflow, and icing. This study revealed the advantages of airborne LiDAR in monitoring the evolution of periglacial phenomena and provided a new insight on the development mechanisms of the phenomena by combining LiDAR with geophysics and field observation. The results of our study are of great significance for developing disaster countermeasures and ensuring the safe operation of buried pipelines.

Hydrus-1D Model for Simulating Potassium Transport in Rice Crop Irrigated with Alternate Wetting and Drying Practice

ABSTRACT Potassium (K) is one of the essential nutrients that play a crucial role in rice fields; however, its availability, transport, and balance components can be influenced by alternating wetting and drying (AWD) irrigation practice. This study used the Hydrus-1D solute transport model to simulate K transport and balance components in AWD irrigated rice fields. Thirty lysimeter field experiment plots with three different irrigation treatments (No: no soil water stress, MS: mild soil water stress (400 cm), and SS: severe soil water stress (750 cm)) were used for rice cultivation. Daily measurements of soil matric potential head (SMPH) and ponding water depth (PWD) were recorded. Throughout the rice-growing season, leachate water samples from the surface (ponding water) and soil profiles were collected to measure K content. Using the lysimeter field experiment data, the Hydrus-1D model simulated K transport in the AWD rice field. The simulation results indicate that the K distribution predominantly occurred within the top puddled soil layer (0–20 cm) in AWD practice. This suggests that the recommended K fertilizer dose with a 4–5 cm PWD and SMPH of 400 cm optimizes K availability for rice while limiting K leaching loss. The Hydrus-1D model proves to be a valuable management tool, aiding in determining optimal K application rates and ponding water depths for AWD irrigation, ensuring sufficient K nutrients for rice, and controlling K loss for sustainable rice production.

Sea ice melt pond bathymetry reconstructed from aerial photographs using photogrammetry: a new method applied to MOSAiC data

Abstract. Melt ponds are a core component of the summer sea ice system in the Arctic, increasing the uptake of solar energy and impacting the ice-associated ecosystem. They were thus one of the key topics during the 1-year drift campaign Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) in the Transpolar Drift 2019/2020. Pond depth is a dominating factor in describing the surface meltwater volume; it is necessary to estimate budgets and used in model parameterization to simulate pond coverage evolution. However, observational data on pond depth are spatially and temporally strongly limited to a few in situ measurements. Pond bathymetry, which is pond depth spatially fully resolved, remains unexplored. Here, we present a newly developed method to derive pond bathymetry from aerial images. We determine it from a photogrammetric multi-view reconstruction of the summer ice surface topography. Based on images recorded on dedicated grid flights and facilitated assumptions, we were able to obtain pond depth with a mean deviation of 3.5 cm compared to manual in situ observations. The method is independent of pond color and sky conditions, which is an advantage over recently developed radiometric airborne retrieval methods. It can furthermore be implemented in any typical photogrammetry workflow. We present the retrieval algorithm, including requirements for the data recording and survey planning, and a correction method for refraction at the air–pond interface. In addition, we show how the retrieved surface topography model synergizes with the initial image data to retrieve the water level of individual ponds from the visually determined pond margins. We use the method to give a profound overview of the pond coverage on the MOSAiC floe, on which we found unexpected steady pond coverage and volume. We were able to derive individual pond properties of more than 1600 ponds on the floe, including their size, bathymetry, volume, surface elevation above sea level, and temporal evolution. We present a scaling factor for single in situ depth measurements, discuss the representativeness of in situ pond measurements and the importance of such high-resolution data for new satellite retrievals, and show indications for non-rigid pond bottoms. The study points out the great potential to derive geometric properties of the summer sea ice surface emerging from the increasingly available visual image data recorded from uncrewed aerial vehicles (UAVs) or aircraft, allowing for an integrated understanding and improved formulation of the thermodynamic and hydrological pond system in models.

Designing Effective Low-Impact Developments for a Changing Climate: A HYDRUS-Based Vadose Zone Modeling Approach

Low-Impact Developments (LIDs), like green roofs and bioretention cells, are vital for managing stormwater and reducing pollution. Amidst climate change, assessing both current and future LID systems is crucial. This study utilizes variably saturated flow modeling with the HYDRUS software (version 4.17) to analyze ten locations in Ontario, Canada, focusing on Toronto. Historical and projected climate data are used in flow modeling to assess long-term impacts. Future predicted storms, representing extreme precipitation events, derived from a regional climate model, were also used in the flow modeling. This enabled a comprehensive evaluation of LID performance under an evolving climate. A robust methodology is developed to analyze LID designs, exploring parameters like water inflow volumes, peak intensity, time delays, runoff dynamics, and ponding patterns. The findings indicate potential declines in LID performance attributed to rising water volumes, resulting in notable changes in infiltration for green roofs (100%) and bioretention facilities (50%) compared to historical conditions. Future climate predicted storms indicate reduced peak reductions and shorter time delays for green roofs, posing risks of flooding and erosion. Anticipated extreme precipitation is projected to increase ponding depths in bioretention facilities, resulting in untreated stormwater overflow and prolonged ponding times exceeding baseline conditions by up to 13 h at numerous Ontario locations.

Egg Quality and Fecundity of Clarias gariepinus Broodstock Cultured at Different Water Depths in Indoor Concrete Tanks

Aims: To investigate the fecundity and egg quality of C. gariepinus broodstock raised at 0.50 m, 0.75 m and 1.0 m pond water depth. Study Design: Treatments were assigned using complete randomized design. Place and Duration of Study: Fish Farm Complex of the Akwa Ibom State University (AKSU), Nigeria. Methodology: Nine female broodstock of C. gariepinus averaging 2.51 – 2.53 kg and 64.30 – 67.24 cm were raised for six months at 0.50 m, 0.75 m and 1.0 m pond water depth; referred to as treatments A, B and C, respectively Experimental fish were fed 42% crude protein commercial feed. The fecundity, relative fecundity, gonadosomatic index (GSI), egg weight and size were assessed. Results: The results revealed that the egg quality significantly (P=.00) increased with the water depth of the broodstock culture tank. Egg weight and GSI values from treatment C (363.40±0.57 g and 14.40±0.01 %, respectively) were significantly (P = .007) higher than those of treatment A (267.30±0.06 g and 10.66± 0.06 %, respectively) but showed no significant difference with those of Treatment B (331.07±1.20; 13.09±0.04 %). The corresponding egg diameter (1.01±00; 1.08±0.03 and 1.21± 0.01g), fecundity and relative fecundity of broodstock also increased with pond water depth (P = .003): 182,120.0±503.67, 72.66±0.40 > 185,618.3± 745.98, 73.37±0.18 > 188, 967.1± 295.19, 74.89±0.18, respectively. Conclusion: The water depth of the broodstock maintenance pond enhances fecundity and egg quality; it is better at 1.0 m depth for successful fry production. Broodstock may be maintained at lower pond water depths for growth purposes; prior to breeding.

Influence of Tank Water Depths on Reproductive Performance of Catfish (Heterobranchus longifilis) Valenciennes, 1840

Aims: To determine the optimum water depth required for catfish spawning in hatcheries. Study Design: Treatments were assigned using complete randomized design. Place and Duration of Study: Fish Farm Complex of the Akwa Ibom State University (AKSU), Nigeria. Methodology: Eighteen (18) similarly-sized H. longifilis broodstock (2.51-2.53 kg, 64 – 66 cm): comprising six broodstock of three males and three females, were held for six months at 0.50 m, 0.75 m and 1.0 m pond water depth. All males were sacrificed for milt extraction without hormonal inducement; with milt from each treatment diluted with normal saline solution. Female broodstock from each treatment were separately induced with ovaprim hormones at a single dosage of 0.5ml/kg body weight of fish and allowed for 16 hours before manual stripping; 3g of egg from each broodstock and mixed with the diluted milt and activated with 100 ml of normal saline. The fertilized eggs were incubated and thereafter assessed for percentage fertilization, hatchability, survival and fry production success. Results: broodstock reproductive parameters significantly increased (P = 0.00) with water depth of broodstock culture tank. Percentage fertilizations were: 49.50±0.78, 68.17±0.93, and 82.50±1.44; respectively. Percentage hatchability of broodstock eggs were: 91.37±1.65 significantly higher for 1.0 m water depth group than 67.79±4.58 from 0.75 m water depth treatment while the least value of hatchability 50.31± 0.78 was recorded for broodstock raised at 0.50 m water depth. The fish group raised at 1.0 m water depth also exhibited highest percentage survival value of 97.02 ± 1.09 and fry production success value of 73.08 ± 0.53 while broodstock raised at 0.50 m water depth indicated the least values: % survival, 8.38 ± 0.48 and fry production success of 2.07 ± 0.07. Conclusion: In times or places of water scarcity, H. longifilis broodstock may be raised at pond water of 0.5 m to 1.0 m. But the water depth that would afford the best breeding and reproductive performance is at 1.0 m depth.

Estimating distributed autumn irrigation water use in a large irrigation district by combining machine learning with water balance models

Autumn irrigation (AI) after crop harvesting is vital for agricultural production in cold arid regions, typically requiring more water than regular irrigation during crop growth phases. Understanding distributed AI water use (AIWU) is key to optimizing irrigation strategies and refining agro-hydrological simulations. However, field-scale monitoring of irrigation water use is challenging, particularly in large districts, and quantification methods for distributed AIWU have seldom been investigated. Given this, we proposed a remote sensing-based model to estimate AIWU from water balance analysis, with key components derived through machine learning algorithms. Specifically, to address the unique challenge of short water ponding duration during AI, we selected MODIS as the primary data source, supplemented with Sentinel-2 data to enrich field-level details. A Sentinel-2 empirical bathymetry model, informed by in-situ measurements, served as a foundation for constructing a MODIS bathymetry model using random forest. This MODIS bathymetry model was essential for determining water ponding depths, which allowed for accurate estimation of infiltration rates when applied to the MODIS-based water index time series. By integrating these estimates into the water balance framework, we achieved a more precise estimate of AIWU. The proposed model was applied to Hetao Irrigation District (HID), the largest irrigation district in the arid region of China. The estimated steady infiltration rate and canal efficiency align with similar studies. The results indicate that the average AIWU per unit AI area in the HID remains stable during 2010–2020 with substantial spatial variability at the pixel level, providing new insights into the local hydrological cycle. The AIWU of HID has been decreasing by 19 million m3 per year during this period mainly due to the reduction in AI area, with a more prominent trend from 2010 to 2017. Our study deepens insights into the spatial–temporal dynamics of AIWU in arid regions, contributing to better irrigation management.

Simulating the Responses of Rice Yield and Nitrogen Fates to the Ground Cover Rice Production System under Different Precipitation Year Types

The ground cover rice production system (GCRPS) has considerable potential for securing rice production in hilly mountainous areas. However, its impact on yields and N fates remains uncertain under varying rainfall conditions. A two-year field experiment (2021–2022) was carried out in Ziyang, Sichuan Province, located in the hilly mountains of southwest China. The experiment included two cultivation methods: conventional flooding paddy (Paddy, W1) and GCRPS (W2). These methods were combined with three N management practices: N1, no-N fertilizer; N2, 135 kg urea N per hm2 as a base fertilizer; and N3, 135 kg urea N per hm2 with split application for W1 and 67.5 kg N per hm2 of urea and chicken manure separately for W2. The WHCNS (soil water heat carbon nitrogen simulator) model was calibrated and validated to simulate ponding water depth, soil water storage, soil mineral N content, leaf area index, aboveground dry matter, crop N uptake, and rice yield. Subsequently, this model was used to simulate the responses of rice yield and N fates to GCRPS under different precipitation year types using meteorological data from 1980 to 2018. The results indicated that the WHCNS model performed well in simulating crop growth and N fates for both Paddy and GCRPS. Compared with Paddy, GCRPS reduced N leaching (35.1%–54.9%), ammonia volatilization (0.7%–13.6%), N runoff (71.1%–83.5%), denitrification (3.8%–6.7%), and total N loss (33.8%–56.9%) for all precipitation year types. However, GCRPS reduced crop N uptake and yield during wet years, while increasing crop N uptake and yield during dry and normal years. Fertilizer application reduced the stability and sustainability of rice yield in wet years, but increased the stability and sustainability of rice yield in dry and normal years. In conclusion, GCRPS is more suitable for normal and dry years in the study region with increasing rice yield and reducing N loss.

Precondition Study of a Sponge City: Comprehensive Assessment of the Vulnerability of an Urban Rainwater System

This study introduces the concept of urban rainwater system vulnerability and identifies the indicator factors that affect the vulnerability of rainwater systems. Using the analytic hierarchy process (AHP), an index system for the vulnerability assessment of the rainwater system was established, and a vulnerability assessment model for the rainwater system was constructed. By integrating vulnerability degree, recurrence period, and water depth of ponding, a vulnerability assessment framework for urban rainwater systems was developed. Taking a newly developed urban area in the Suzhou High-Tech Zone as an example, we calculated the vulnerability degree of the urban rainwater system in this area to be 0.6497, indicating a high level of vulnerability and poor system safety. When encountering rainfall with a recurrence period p > 5 years, the city is likely to experience severe waterlogging. Through the analysis and evaluation of the rainwater system’s vulnerability, while clarifying the current state of the rainwater system, it can provide a scientific reference basis for the system’s upgrade, transformation, and optimized operation and management. Although the selection of factors may not be entirely comprehensive, this method allows for adjustments based on the composition and operation of different rainwater systems.

Exploitation and survival of Yellow Perch introduced into community ponds

Increased urbanization paired with stagnant or decreasing fishing license sales has bolstered the importance of community fishing programs. Community fisheries require fish introductions, have highly variable chemical and physical characteristics, and are situated in urban settings with non-traditional fishers that can prefer unique species. Community ponds also often receive high angling pressure and exploitation that can hinder the establishment of sustainable populations. We evaluated angler exploitation and its effects as well as biotic (i.e., stocking density, predator relative abundance) and abiotic (i.e., water temperature, pond size, pond depth) factors affecting survival of stocked adult Yellow Perch Perca flavescens in community ponds. We tagged 580 adult Yellow Perch (≥150 mm) and stocked them into four community ponds at 74 or 148 fish/ha in September 2018. We collected two years of fishery dependent (angler tag reporting) and independent recapture data to estimate angler exploitation and survival of Yellow Perch using a joint live-recapture and dead-recovery model. We estimated anglers harvested 44% (95% CI ± 6%) of stocked Yellow Perch across the four ponds in two years, with the majority (81%) coming from one pond. Additionally, anglers harvested 66% of captured Yellow Perch and harvest probability increased with fish size. Seasonal exploitation ranged from 0% to 37% and was more prevalent in cold water seasons. Yellow Perch survival was negatively related to harvest (β = −0.14; 95% CI = −0.17 to −0.10) and a quadratic effect of water temperature (temperature: β = 0.28; 95% CI = 0.02–0.53; temperature2: β = 0.01; 95% CI = −0.01–0.01). Yellow Perch survival was not related to stocking density or pond characteristics. After two years, cumulative survival in three ponds ranged from 0.83 to 0.87 whereas survival in one pond with high exploitation was 0.22. Our results suggest Yellow Perch can be successfully introduced in community fisheries, but populations may not be sustainable when harvest is high. Thus, management strategies to mitigate excessive harvest or multiple put-and-take stockings may be necessary to maintain Yellow Perch populations in community fishing programs.

Monitoring and risk assessment of Taoyuan ponds using an unmanned surface vehicle with multibeam echo sounder, ground-penetrating radar, and electrical resistivity tomography

Ponds are a unique agricultural irrigation method with a long history in the Taoyuan area. However, most of them lack accurate spatial information, such as water depth, water surface area, and effective water storage capacity. In this study, the water depth of pond was measured using an unmanned surface vehicle, which has the advantage of being able to operate in shallow waters and in areas that are inaccessible to manned boats. The results show that it can rapidly provide 3D point cloud and an underwater 50 cm gridded digital elevation model with an accuracy of 6.7 cm, which can be used to identify structural defects at the pond bed and the embankment and to accurately estimate the water surface area and effective water storage capacity. The nests with diameters of 30 to 70 cm dug by male tilapia to attract female tilapia for spawning can also be found. In addition, the ground-penetrating radar and electrical resistivity tomography were carried out to successfully investigate the electricity-related properties of the internal structure of the embankment and the leakage locations of pond. In conjunction with the maintenance experience of the Taoyuan Management Office, a risk reference index was proposed for the safety management.

Satellite imagery as a management tool for monitoring water clarity across freshwater ponds on Cape Cod, Massachusetts

Water clarity serves as both an indicator and a regulator of biological function in aquatic systems. Large-scale, consistent water clarity monitoring is needed for informed decision-making. Inland freshwater ponds and lakes across Cape Cod, a 100-km peninsula in Massachusetts, are of particular interest for water clarity monitoring. Secchi disk depth (SDD), a common measure of water clarity, has been measured intermittently for over 200 Cape Cod ponds since 2001. Field-measured SDD data were used to estimate SDD from satellite data, leveraging the NASA/USGS Landsat Program and Copernicus Sentinel-2 mission, spanning 1984 to 2022. Random forest machine learning models were generated to estimate SDD from satellite reflectance data and maximum pond depth. Spearman rank correlations (rs) were “strong” for Landsat 5 and 7 (rs = 0.78 and 0.79), and “very strong” for Landsat 8, 9, and Sentinel-2 (rs = 0.83, 0.86, and 0.80). Mean absolute error also indicated strong predictive capacity, ranging from 0.65 to 1.05 m, while average bias ranged from −0.20 to 0.06 m. Long- and recent short-term changes in satellite-estimated SDD were assessed for 193 ponds, selected based on surface area and the availability of maximum pond depth data. Long-term changes between 1984 and 2022 established a retrospective baseline using the Mann-Kendall test for trend and Theil-Sen slope. Generally, long-term water clarity improved across the Cape; 149 ponds indicated increasing water clarity, and 8 indicated deteriorating water clarity. Recent short-term changes between 2021 and 2022 identified ponds that may benefit from targeted management efforts using the Mann-Whitney U test. Between 2021 and 2022, 96 ponds indicated deteriorations in water clarity, and no ponds improved in water clarity. While the 193 ponds analyzed here constitute only one quarter of Cape Cod ponds, they represent 85% of its freshwater surface area, providing the most spatially and temporally comprehensive assessment of Cape Cod ponds to date. Efforts are focused on Cape Cod, but can be applied to other areas given the availability of local field data. This study defines a framework for monitoring and assessing change in satellite-estimated SDD, which is important for both local and regional management and resource prioritization.

Hydroperiod length, not pond age, determines zooplankton taxonomic and functional diversity in temporary ponds

Mediterranean Temporary ponds (MTPs) are suffering severe alterations in their hydrological and salinity regime through global change, and restoration or conservation of these habitats is a priority. However, there is little information that can be used as a scientific basis for restoration.We studied the taxonomic and functional diversity of zooplankton communities in a set of 96 ponds in Doñana, Spain during four consecutive hydroperiods after their creation. We examined the differences across hydroperiods in alpha and beta diversity (and its turnover and nestedness components) of the rotifer, cladoceran and copepod community, as well as the influence of local environmental variables including the proximity to natural wetlands.There was no general increase in diversity indices after the first two hydroperiods. We found that shorter hydroperiods significantly reduced taxonomic diversity, but increased the contribution to functional beta diversity through turnover. Shorter hydroperiods also reduced community complexity, with long-term effects. Conductivity was the most important predictor of zooplankton alpha and beta diversity, but the direction of its effects changed between hydroperiods. The distance from a natural source of colonists, and pond depth, were key during the early stage of community assembly and after a hydrological perturbation.Our results suggest that new restoration projects for MTPs should focus on increasing local environmental heterogeneity and on reducing vulnerability to salinization.The use of functional approaches in monitoring studies can improve our understanding of mechanisms and processes affecting zooplankton community assembly under dynamic hydrological regimes. This in turn can help us predict the consequences of management and restoration policies for biodiversity conservation in MTPs.

Model test on frost heaving pressure induced by frozen partial ponding behind tunnel lining in cold region

For tunnels in a cold region, the research of frost heaving-induced pressure (FHIP) due to frozen partial ponding is carried out based on certain theoretical assumptions. However, there is few research using the laboratory experiment to investigate the evolution of FHIP with time and space. Therefore, in this paper, to study the mechanism of the FHIP induced by frozen partial ponding of tunnel in the cold region, a three-dimensional geotechnical model test equipment only considering frost heave loads on lining is developed, in which the cold air of environment can be blown into the tunnel. Accordingly, the variation law of FHIP and the temperature field in the surrounding rock under the freezing condition are discussed. Moreover, a three-dimensional cone shape constrained model is developed to predict FHIP by considering the differences of the ponding depth, the stiffness of the surrounding rock and lining, which is further validated by comparing with experimental data. Results indicate that when the FHIP occurs, the temperature in the surrounding rock starts to drop rapidly with time. This proposed model can evaluate the FHIP caused by a frozen partial ponding with any cone shape and size. To account for the effect of time, the theoretical and semi-empirical model is further developed based on the three-dimensional cone shape constrained model. Comparisons with experimental data demonstrate that the modified theoretical and semi-empirical model well predict the evolution law of FHIP. This research can provide theoretical references to reveal the spatio-temporal evolution of the FHIP for partial ponding of tunnels in the cold region.

Rainstorm Resistance of Recycled Pervious Concrete under the Coupling of Fatigue and Freeze–Thaw Cycles

In order to alleviate the increasing serious urban waterlogging problem, the rainstorm resistance of a new self-compacting recycled pervious concrete (NSRPC) under the coupling of freeze–thaw (F-T) and fatigue is studied. The once-in-a-century rainfall was simulated, and the rainstorm resistance of NSRPC was evaluated mainly through the ponding depth and drainage time. In addition, the mechanical properties (compressive strength and flexural strength), mass loss rate and relative dynamic elastic modulus of NSRPC during F-T and fatigue coupling were measured. The microstructure of NSRPC was observed by scanning electron microscopy, and its deterioration mechanism was analyzed. The results show that the fatigue load aggravates the F-T damage of NSRPC in the later stage. With the increase in the number of fatigue cycles, the loss rate of compressive strength and flexural strength of NSRPC increases continuously, and the permeability coefficient decreases first and then increases. With the increase in the number of freeze–thaw and fatigue cycles, the mass loss rate increases gradually, and the relative dynamic elastic modulus decreases gradually. After the coupling of fatigue and F-T cycles, the minimum mass loss of NSRPC is only 2.14%, and the relative dynamic elastic modulus can reach 86.2%. The increase in the number of fatigue cycles promotes the generation and expansion of micro-cracks and provides more channels for water to invade the matrix. Under the action of rainstorm in the 100-year return period, the maximum ponding depth of NSRPC with steel fiber content is 84 mm, and the drainage time is 7.1 min, which meets the needs of secondary highway. This study will provide theoretical basis for improving the service life and drainage capacity of urban drainage pavement in cold areas.