Most old urban areas of China have a dense population, severely indurated underlying surface, and highly developed underground space. Those increase the waterlogging risk and obstruct the stormwater management in old urban areas. To propose an appropriate engineering strategy for low impact development (LID) transformation in an urban area, a simulation was carried out by storm water management model (SWMM) in this project. Bioretention cells, permeable pavements, and green roofs were selected according to the study area surface. Runoff control performance of single LID control and combined schemes were compared. Results illustrate that only 50.21% of roofs can build green roofs in urban areas with dense populations, and the runoff control performance of green roofs is unsatisfactory, while bioretention cells and permeable pavements can effectively mitigate runoff caused by storms with a recurrence period less than 10 years, and combined LID controls can obtain better runoff control performance with less construction area. Those outcomes screened out the LID controls suitable for application in densely populated old urban areas and put forward reasonable engineering practice strategies. This study provides guidance and reference for the LID transformation in the densely populated old urban area. Full article

Water is an imperative part of the Earth and an essential resource in human life and production. Under the effects of climate change and human activities, the spatial and temporal distribution of water bodies has been changing, and the shortage of water resources is becoming increasingly serious worldwide. Therefore, the monitoring of water bodies is indispensable. Remote sensing has the advantages of real time, wide coverage, and rich information and has become a brand-new technical means to quickly obtain water information. This study summarizes the current common methods of water extraction based on optical and radar images, including the threshold method, support vector machine, decision tree, object-oriented extraction, and deep learning, as well as the advantages and disadvantages of each method. These methods were applied to the Huai River Basin in China and Nam Co on the Qinghai-Tibet Plateau. The extraction results show that all the aforementioned approaches can obtain reliable results. Among them, the threshold segmentation method based on normalized difference water index is more robust than others. In the water extraction process, there are still many problems that restrict the accuracy of the results. In the future, researchers will continue to search for more automatic, extensive, and high-precision water extraction methods. Full article

This study presents an integrated analysis of cohesive bank-collapsed material transportation in a high-curvature channel with a non-cohesive riverbed. A numerical model was established to simulate the erosion and transportation of collapsed materials in a 180° U-bend channel after verification. The novel aspect of this study is that the quantities of the collapsed materials that transformed into suspended and bed loads were comprehensively analyzed. The results show that finer collapsed sediments were only transformed into suspended loads after being eroded, while the coarser particles transformed into both suspended loads and bed loads. When the flow charge was 30 L/s, the quantity of collapsed materials (S1 and S2) that transported downstream was smaller, and coarser materials transformed into suspended loads with a ratio of 88.12–99.86% and bed loads with a ratio of 11.18–0.14%. When the flow charge was 55 L/s, due to the greater shear stress, the quantity of collapsed materials (S1 and S2) that transported downstream was greater, and the ratio ranged from 46.65% to 49.88% and from 50.12% to 53.35%, respectively. This research provides theoretical and practical benefits that reveal the mechanisms of channel bend evolution. Full article

The implementation of a 0.5% mass/mass sulphur cap in fuels used by ships has become a reality. Furthermore, regulation 14 of the MARPOL Convention–Annex VI (amended) establishes that the limit on fuel used by ships operating in a Sulphur Emission Control Area (SECA) cannot exceed 0.1% of mass/mass. To deal with these requirements while considering nature of the shipping business, which is the continuous carriage of cargo around the world, shipowners or shipping companies have few options for following this regulation. Apart from the use of a low-sulphur-content fuel is the use of an exhaust-gas cleaning system, also known as “scrubbers”, as an alternative. The use of these systems, specifically the open-loop system, entails the discharge to the sea of residual water used during the cleaning process of exhaust gases from ship engines. The objective of this paper is to study the effect produced by discharging this residual water on the acidity level (pH) of Barcelona port water. This objective was achieved through the periodical sampling and analysis of Barcelona port water in collaboration with the IDAEA (CSIC) laboratory. We analysed the evolution of the pH results obtained so far and obtained an initial picture of the pH Barcelona port water situation in real time regarding the effect of wash-water discharges from open-loop scrubbers. Furthermore, this paper describes the implementation of a system which is going to improve the operation of open-loop exhaust-gas cleaning systems. Full article

The thirty-eight-year record (1984–2021) of glacier mass balance measurement indicates a significant glacier response to climate change in the North Cascades, Washington that has led to declining glacier runoff in the Nooksack Basin. Glacier runoff in the Nooksack Basin is a major source of streamflow during the summer low-flow season and mitigates both low flow and warm water temperatures; this is particularly true during summer heat waves. Synchronous observations of glacier ablation and stream discharge immediately below Sholes Glacier from 2013–2017, independently identify daily discharge during the ablation season. The identified ablation rate is applied to glaciers across the North Fork Nooksack watershed, providing daily glacier runoff discharge to the North Fork Nooksack River. This is compared to observed daily discharge and temperature data of the North Fork Nooksack River and the unglaciated South Fork Nooksack River from the USGS. The ameliorating role of glacier runoff on discharge and water temperature is examined during 24 late summer heat wave events from 2010–2021. The primary response to these events is increased discharge in the heavily glaciated North Fork, and increased stream temperature in the unglaciated South Fork. During the 24 heat events, the discharge increased an average of +24% (±17%) in the North Fork and decreased an average of 20% (±8%) in the South Fork. For water temperature the mean increase was 0.7 °C (±0.4 °C) in the North Fork and 2.1 °C (±1.2 °C) in the South Fork. For the North Fork glacier runoff production was equivalent to 34% of the total discharge during the 24 events. Ongoing climate change will likely cause further decreases in summer baseflow and summer baseflow, along with an increase in water temperature potentially exceeding tolerance levels of several Pacific salmonid species that would further stress this population. Full article

The use of feedstock crops for the production of biodiesel suggests that biodiesel production may have a major impact on the scarce freshwater resource in South Africa. This paper aimed to assess the green plus blue water footprints (WF_green+blue) of biodiesel produced from sunflower in South Africa using the Global Water Footprint Standard approach. The green (WF_green) and blue water footprint (WF_blue) at the farm level were assessed for sunflower grown under the rain-fed and irrigation production system respectively. The results show that 2617 m³ and 2477 m³ are required to produce 1 ton of rain-fed and irrigated sunflower respectively. At the processing level, about 7.12 L of blue water is required to produce 1 L of biodiesel from sunflower. The WF_blue at the processing stage of biodiesel produced from irrigated sunflower was 1.01 m³/GJ, compared to 1.15 m³ m³/GJ from rain-fed sunflower. The WF_green+blue of biodiesel produced from irrigated and rainfed sunflower was 2477 and 2617 m³/ton, respectively. WF_green was the largest, accounting for about 59% and 99% for biodiesel produced from irrigated and rain-fed sunflower, respectively. It was further found that water consumption at the farm level accounted for about 99% of the WF_green+blue of biodiesel in both production systems. Management practices that improve water use efficiency at the farm level may help to lower the WF_green+blue of biodiesel. Interestingly, the WF_green+blue is lower for biodiesel produced from irrigated sunflower than for rainfed sunflower. The blue water scarcity assessment showed that blue water scarcity is low during the period when sunflower requires water. As such, purely from a water use perspective, irrigated sunflower production in the Orange Riet Irrigation Scheme may be considered sustainable. Full article

Urban flooding poses risks to the safety of drivers and pedestrians, and damages infrastructures and lifelines. It is important to accommodate cities and local agencies with enhanced rapid flood detection skills and tools to better understand how much flooding a region may experience at a certain period of time. This results in flood management orders being announced in a timely manner, allowing residents and drivers to preemptively avoid flooded areas. This research combines information received from ground observed data derived from road closure reports from the police department, with remotely sensed satellite imagery to develop and train machine-learning models for flood detection for the City of San Diego, CA, USA. For this purpose, flooding information are extracted from Sentinel 1 satellite imagery and fed into various supervised and unsupervised machine learning models, including Random Forest (RF), Support Vector Machine (SVM), and Maximum Likelihood Classifier (MLC), to detect flooded pixels in images and evaluate the performance of these ML models. Moreover, a new unsupervised machine learning framework is developed which works based on the change detection (CD) approach and combines the Otsu algorithm, fuzzy rules, and iso-clustering methods for urban flood detection. Results from the performance evaluation of RF, SVM, MLC and CD models show 0.53, 0.85, 0.75 and 0.81 precision measures, 0.9, 0.85, 0.85 and 0.9 for recall values, 0.67, 0.85, 0.79 and 0.85 for the F1-score, and 0.69, 0.87, 0.83 and 0.87 for the accuracy measure, respectively, for each model. In conclusion, the new unsupervised flood image classification and detection method offers better performance with the least required data and computational time for enhanced rapid flood mapping. This systematic approach will be potentially useful for other cities at risk of urban flooding, and hopefully for detecting nuisance floods, by using satellite images and reducing the flood risk of transportation design and urban infrastructure planning. Full article

The analysis of common properties of growth for crops is the basis for further understanding crop growth in different regions. We used four typical crops of China, winter wheat, summer maize, rice, and cotton, to build an integrated model suitable for simulating the growth of different crops. The rates and characteristics of crop growth were systematically analysed based on semirelative and fully relative logistic models of crop growth, and a comprehensive, fully relative logistic model for the four crops was established. The spatial distributions of the maximum leaf area index (LAI_max) and maximum dry-matter accumulation (DMA_max) for the four crops were analysed. The semirelative and fully relative growth models exhibited different characteristics of crop growth. The essential characteristics of growth and the characteristics of the crops at each stage of growth were better represented by the fully relative logistic growth model than by the semirelative model. The comprehensive, fully relative logistic model fitted the growth of all four crops well. LAI_max and DMA_max varied greatly amongst the four crops and were strongly regionally distributed. These indicators for the same crop were differentially spatially variable, and the two indicators were not significantly correlated, except for rice. LAI_max and DMA_max in different regions could be obtained using a binary quadratic equation of water consumption and growing degree days for the crops. This study provides a novel method for quantitatively judging the status of crop growth, predicting crop yields, and planning for regional agricultural planting. Full article

Freshwater macroalgae produces a wide range of bioactive compounds, and interest in utilizing its biomass is growing rapidly. Meanwhile, exploiting renewable sources for biomass collection could lead to more sustainable biotechnological chains. The aim of this study was to investigate Cladophora glomerata biomass from Lithuanian rivers as a potential raw material for biotechnology. For this reason, phenolic compound profiles, antioxidant activity and pigment concentrations were determined in macroalgal biomass samples collected from the following four Lithuanian rivers: Dubysa (B1), Šventoji (B2), Nevėžis (B3) and Jūra (B4). The highest total phenolic compound content was determined in B3 (1.32 mg GAE/g). Three phenolic acids were identified, namely gallic (12.94–35.13 µg/g), p-hydroxybenzoic (23.97–29.05 µg/g) and p-coumaric (1.79–6.46 µg/g). The results indicate significant C. glomerata antioxidant activity; the highest reducing power reached 0.737 AU (B3), the total antioxidant content was 1.47 mg Trolox/g (B3), DPPH and ABTS radical scavenging was 11.09% (B3) and 97.86% (B1) and FRAP activity 20.86 µmol/L (B3). The content of pigments ranged from 0.56-0.74, 0.39–0.57, 0.17–0.23 to 0.11–0.17 mg/g in chlorophyll a, b, carotenoids, and lutein, respectively. To conclude, C. glomerata macroalgal biomass may have the potential to act as a functional raw material, as several groups of bioactive compounds and antioxidant activities were observed. Full article

In recent decades, groundwater overexploitation has caused an important aquifer level decline in arid zones each year. In addition to this issue, large volumes of effluent are produced each year in metropolitan areas of these regions. In this situation, an aquifer storage and recovery system (ASR) using the reclaimed domestic wastewater can be a local solution to these two challenges. In this research, a post-treatment of reclaimed municipal wastewater has been investigated through unsaturated–saturated porous media. A large-scale, L-shaped experimental model was set up near the second-stage wastewater treatment plant (WWTP) in the west of greater Tehran. The water, soil, and treated wastewater of the experimental model were supplied from the aquifer, site, and WWTP, respectively. The 13 physicochemical parameters, temperature and fecal coliform were analyzed every 10 days in seven points for a period of four months (two active periods of 40 days with a 12-h on–off rate (wet cycles) and a rest period of 40 days (dry cycle) between the two wet cycles). The results showed that the effects of the saturated zone were twice as great as those of the unsaturated zone and two-thirds of the total treatment efficiency. Furthermore, a discontinuous wet–dry–wet cycle had a significant effect on effluent treatment efficiency and contaminants’ reduction. In conclusion, an aquifer storage and recovery system using treated wastewater through the unsaturated–saturated zones is a sustainable water resource that can be used for agriculture, environmental and non-potable water demands. Full article

Exogenous drivers may cause a gradual and reversible change in a lake equilibrium, or they may force it over a threshold to a persistent alternative stable state, described as a regime shift in the ecosystem. In the mid-and-lower Yangtze River Basin (MLYB), major environmental problems in shallow lakes have been eutrophication and abrupt algal blooms under anthropogenic disturbances for the recent century. Much value is therefore placed on understanding the changes in shallow-lake ecosystems that characteristically precede changes in the state of the lake. Here, we describe a case study of the paleolimnological signature in diatom assemblages of various types of regime shifts caused by historically documented anthropogenic drivers in a temperate shallow lake: Taibai Lake. We evaluate the effectiveness of paleolimnological data as a surrogate for long-term monitoring. Algorithms using sequential t and F statistics detected breakpoints in the time series of diatom assemblages, in 1994–1996, 1974–1977, 1952–1956, and 1931–1934, respectively. The regression statistics suggest that the hydrodynamic–ecosystem and aquacultural–ecosystem relationships fit better in the breakpoint regression model, and the relationship between nutrient loading and ecosystem state suits the linear model. Feedback loops help reconstruct dynamic changes in Taibai influenced by major stressors. Our study exemplifies the value of system approaches to identifying regime shifts and their possible causes in shallow lakes from paleolimnological records. The case study of Taibai set an example of reconstructing the ecological regime shifts in shallow lakes in the MLYB and understanding the state changes in lake ecosystems, which will benefit effective lake management. Full article

This study investigated the hydrodynamics of a solitary wave passing a vertical cylinder over a viscous mud bed for the first time. A highly viscous Newtonian fluid was assumed as a simplified model for fluid mud. A three-dimensional numerical wave flume consisting of a fixed cylindrical structure and three viscous fluids—air, water, and mud—was constructed and validated. Numerical experiments were performed to investigate solitary wave interaction with a vertical cylinder over a viscous mud bed. Numerical results showed the mud surface deformation to be one order of magnitude smaller than the water surface deformation and their behaviors to be different: mud surface depressions occurred on the upstream and downstream sides of the cylinder, whereas mud surface elevations occurred on the lateral sides of the cylinder. This solitary wave induced scour pattern on a muddy seabed is different from that commonly observed on a sandy seabed. Water flow reversal near the water–mud interface was made more evident by the mud bed. Although the mud bed attenuated water waves, it nevertheless increased the total horizontal force and toppling moment exerted on the cylinder due to the wave-induced mud flow. These findings may be valuable to the design of marine structures on a muddy seabed and worthy of further investigation. Full article