The contiguous United States (CONUS), especially the West, faces challenges of increasing water stress and uncertain impacts of climate change. The historical information of surface water body ...distribution, variation, and multidecadal trends documented in remote-sensing images can aid in water-resource planning and management, yet is not well explored. Here, we detected open-surface water bodies in all Landsat 5, 7, and 8 images (∼370,000 images, >200 TB) of the CONUS and generated 30-meter annual water body frequency maps for 1984–2016. We analyzed the interannual variations and trends of year-long water body area, examined the impacts of climatic and anthropogenic drivers on water body area dynamics, and explored the relationships between water body area and land water storage (LWS). Generally, the western half of the United States is prone to water stress, with small water body area and large interannual variability. During 1984–2016, water-poor regions of the Southwest and Northwest had decreasing trends in water body area, while water-rich regions of the Southeast and far north Great Plains had increasing trends. These divergent trends,mainly driven by climate, enlarged water-resource gaps and are likely to continue according to climate projections. Water body area change is a good indicator of LWS dynamics in 58% of the CONUS. Following the 2012 prolonged drought, LWS in California and the southern Great Plains had a larger decrease than surface water body area, likely caused by massive groundwater withdrawals. Our findings provide valuable information for surface water-resource planning and management across the CONUS.
AbstractWater resources are crucial for human activities and sustainable socioeconomic development. Understanding surface water information can play a key role in water resource management, which ...affects the global water cycle and ecological environments. Considering the Hailar River water body as an example, this study proposes a new threshold self-learning water body extraction method (TSLWEM) based on modified normalized difference water index (MNDWI) data. The optimal water extraction thresholds determined by the TSLWEM algorithm for four test images were −0.0030, 0, 0.1990, and −0.0800. The TSLWEM algorithm effectively identified the target water body with recognition accuracies of 98.08%, 99.93%, 93.39%, and 93.20% for the four test images. Moreover, it can accurately identify small tributaries, such as lakes and rivers. The TSLWEM algorithm is suitable for Landsat 8 Operational Land Imager (OLI) data, which can effectively monitor and map complex surface water in temperate and semiarid regions while improving the accuracy of water body identification. The study’s findings provide technical support for the protection of water resources as well as their rational utilization and monitoring.
This paper describes the development of a Global 3arc-second Water Body Map (G3WBM), using an automated algorithm to process multi-temporal Landsat images from the Global Land Survey (GLS) database. ...We used 33,890 scenes from 4 GLS epochs in order to delineate a seamless water body map, without cloud and ice/snow gaps. Permanent water bodies were distinguished from temporal water-covered areas by calculating the frequency of water body existence from overlapping, multi-temporal, Landsat scenes. By analyzing the frequency of water body existence at 3arc-second resolution, the G3WBM separates river channels and floodplains more clearly than previous studies. This suggests that the use of multi-temporal images is as important as analysis at a higher resolution for global water body mapping. The global totals of delineated permanent water body area and temporal water-covered area are 3.25 and 0.49millionkm2 respectively, which highlights the importance of river-floodplain separation using multi-temporal images. The accuracy of the water body classification was validated in Hokkaido (Japan) and in the contiguous United States using an existing water body databases. There was almost no commission error, and about 70% of lakes >1km2 shows relative water area error <25%. Though smaller water bodies (<1km2) were underestimated mainly due to omission of shoreline pixels, the overall accuracy of the G3WBM should be adequate for larger scale research in hydrology, biogeochemistry, and climate systems and importantly includes a quantification of the temporal nature of global water bodies.
•Global 90-m water body map developed from 33,890 LANDSAT GLS images•Separation of permanent and temporal water bodies by frequency analysis•Better representation of river channels, floodplains, and small lakes.•Use of multi-temporal images is as important as analysis at a higher resolution•Developed dataset is distributed freely for research and education purposes.
Urban open space provides various benefits to citizens, but the thermal environment of this space is impacted by global warming and urban heat islands. A growing number of studies have been conducted ...on strategies for improving the urban thermal environment and attracting more people to outdoor spaces. This paper reviews the mechanisms and cooling effects of four major mitigation strategies, namely, changing the urban geometry, planting vegetation, using cool surface, and incorporating bodies of water. Our review found that on summer days these four strategies yielded a median reduction in air temperature of 2.1 K, 2.0 K, 1.9 K, and 1.8 K, respectively. In terms of integrated effect on thermal comfort, changing the urban geometry provided the greatest improvement, with the largest reduction in physiologically equivalent temperature (PET) in summer (median ΔPET = 18.0 K). The use of vegetation and water bodies reduced the median PET by 13.0 K and 4.6 K, respectively. However, some simulation studies found that reflective surface led to higher PET in summer because of the increased amount of reflected solar radiation. The mitigation strategies improved the urban thermal environment to a greater extent in hotter and drier climates. Vegetation, cool surface, and water bodies provided less cooling in compact urban spaces than in open areas. The results that we reviewed can be used by designers and planners seeking to create thermally comfortable urban open spaces.
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•Reviewed effect of using geometry, vegetation, cool surface, and water bodies•The strategies had a median air temperature reduction of 1.5–2.0 K.•Reviewed simulation results indicate reflective surface increased PET.•The effects of the strategies are better in hotter and drier climates.
Continuous monitoring of reservoirs and dams is essential for efficient water management. Synthetic Aperture Radar (SAR) imagery offers the potential for continuous monitoring of surface water ...through all-weather ground observation. The objective of this study is to enhance the accuracy of water body detection and water quantity estimation by applying 64 combinations of speckle filtering and object detection techniques to Sentinel-1 imagery. For speckle filtering, the Median, Gaussian, Lee, and Frost techniques were used with various window sizes (3, 5, 7, and 9). For water body detection, the Otsu, Kittler-Illingworth (KI), Chan-Vese (CV), and K-means methods were employed. The study area included three reservoirs and two dams in Korea, encompassing a variety of water surface sizes and types of land cover. To validate the accuracy of each water body detection combination, manual delineation-based water mask images from Sentinel-2 were employed. Furthermore, a regression equation (y=axb) between water surface area and storage was used to estimate water storage based on SAR imagery, followed by time-series validation using in-situ data. The research results indicate that the optimal detection technique varies significantly depending on the type of surrounding land cover and the size of the water body. The highest performance was observed for the CV technique combination for waterfront pixels, and for the KI technique combination for other land cover pixels. In speckle filtering techniques using a large window size, the false detection rate caused by vegetation and buildings was low; however, the boundaries of water bodies were blurred. Consequently, using smaller window sizes in SAR imagery and leveraging optimal water body detection combinations specific to land cover types, along with post-processing using masking data, would enhance the performance of water surface area and storage estimation.
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•Reservoirs and dams are monitoring based on SAR images of the Korean peninsula.•64 combinations of speckle filtering and object detection techniques are compared.•Optimal water body detection combination varies by land cover type.•Small window size speckle filtering with masking yields the best results.
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•A New China’s artificial water bodies (WBs) dataset from 1987 to 2020 is developed.•The total area of WB in inland China increased by 38.8% from1987 to 2020.•The artificial area of ...WB in inland China increased by 32.3% from1987 to 2020.•Climate change dominates the WB increasing in the western basins of China.•Most WB changes are controlled by dam construction in the eastern basins of China.
As an important surface water resource that can be directly used, water bodies (WBs) have a non-negligible impact on human life, production and maintaining ecological balance. Over the past few decades, how many WB have changed to different degrees due to climate change, dam construction and other factors? Using the high-resolution WB mask dataset and dam point data, the study distinguished artificial and natural WBs, calculated their spatiotemporal changes, and quantified climatic and human contributions in 17 basins in inland China during 1987–2020. The results show WBs exhibited a spatial pattern of contraction in the northeast and expansion in the southwest in inland China. The total, artificial and natural area of inland WBs in China increased by 38.8%, 32.3%, 40.8% from 1987 to 2020, respectively. In the western basins of China such as Inland rivers in Northern Tibet (61%), Upper Yellow River (61%), Upper Yangtze River (52%), Inland rivers in Xinjiang (51%), climate change dominates the increase of WBs. While in the eastern basins such as the Middle and Lower Yangtze River (60.84%), Lower Yangtze River (60.53%), and Songhua basins (52.66%), dam construction is the main reason for the area change in WBs. The analysis of the spatiotemporal evolution of WBs in inland China in the past three decades and the quantification of climate and human contributions are of great significance for the rational development and sustainable use of water resources.
Wastewater treatment plants (WWTPs) have been appointed as one of the main sources of microplastics (MP) into marine ecosystems. The aim of this research work has been to study the influent and ...effluent of two WWTPs, both located in Cádiz, with different wastewater source (industrial and urban), as well as the receiving water bodies where the facilities discharge their sewage.
MP were collected, extracted from wastewater matrixes and analysed according to the abundance, shape, size, and type of polymer, along with the removal rates of MPs in the plants.
Subsequently, the data obtained on both WWTPs were compared, the main difference among the WWTPs was the amount of microplastics found in the wastewater, as well as the presence of polymers with resins from industrial activities.
The results from this study established that the most representative form was fibers; about the size, 100–355 μm fraction was the most abundant, followed by 355–1000 μm and finally the size among 1000–5000 μm. Regarding to the type of polymers, 17 were identified using attenuated total refraction Fourier-transformed infrared spectroscopy (ATR-FTIR). Further, PVC, PE, EAA and HDPE were the largest found polymers.
The presence of MPs in the influent varied from 645.03 ± 182.24 MPs/L to 1567.49 ± 413.18 MPs/L in the urban and industrial WWTP respectively; in the effluent, it varied from 16.40 ± 7.85 MPs/L to 131.35 ± 95.36 MPs/L. The removal rate overcome the 90% in all the samples.
Receiving water bodies presented heterogeneous abundance of microplastics 6.64 ± 2.71 MPs/L and 0.83 ± 0.26 MPs/L in the zones close to IWWTP and UWWTP discharge point.
The results obtained shows that despite the elimination efficiency in the WWTPs studied, these facilities act as a significant source of MPs into aquatic ecosystem due to large flow of water discharged.
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•Microplastics (MPs) have been widely detected in marine environment.•Wastewater treatment plants (WWTPs) have been pointed out as a source of MPs.•Facilities within the city of Cádiz were studied: an urban and an industrial WWTPs.•Influent, effluent and receiving water were analysed using microscope and FTIR.•MPs were found in all samples; WWTPs studied removed >90% of MPs.
Oklahoma contains the largest number of manmade lakes and reservoirs in the United States. Despite the importance of these open surface water bodies to public water supply, agriculture, ...thermoelectric power, tourism and recreation, it is unclear how these water bodies have responded to climate change and anthropogenic water exploitation in past decades. In this study, we used all available Landsat 5 and 7 images (16,000 scenes) from 1984 through 2015 and a water index- and pixel-based approach to analyze the spatial-temporal variability of open surface water bodies and its relationship with climate and water exploitation. Specifically, the areas and numbers of four water body extents (the maximum, year-long, seasonal, and average extents) were analyzed to capture variations in water body area and number. Statistically significant downward trends were found in the maximum, year-long, and annual average water body areas from 1984 through 2015. Furthermore, these decreases were mainly attributed to the continued shrinking of large water bodies (>1km2). There were also significant decreases in maximum and year-long water body numbers, which suggested that some of the water bodies were vanishing year by year. However, remarkable inter-annual variations of water body area and number were also found. Both water body area and number were positively related to precipitation, and negatively related to temperature. Surface water withdrawals mainly influenced the year-long water bodies. The smaller water bodies have a higher risk of drying under a drier climate, which suggests that small water bodies are more vulnerable under climate-warming senarios.
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•All Landsat 5/7 images were used to generate water body frequency maps.•Water body variability in maximum, year-long, seasonal, and average water extents•Both water body area and number decreased significantly during 1984–2015.
There is a growing concern on the fate and the consequent ecological or health risks of antibiotics and antibiotic resistance genes (ARGs) in natural or artificial water environment. The effluent of ...wastewater treatment plants (WWTPs) has been reported to be an important source of antibiotics and ARGs in the environment. WWTP effluent could be discharged into surface water bodies or recycled, either of which could lead to different exposure risks. The impact of WWTP effluents on the levels of antibiotics and ARGs in effluent-receiving water bodies and the removal efficiency of antibiotics and ARGs in reclaimed wastewater treatment plants (RWTPs) were seldom simultaneously investigated. Thus, in this study, we investigated the occurrence of antibiotics and ARGs in four WWTP effluents, and their downstream effluent-receiving water bodies and RWTPs in seasons of low-water-level. The total concentrations of ofloxacin, norfloxacin, ciprofloxacin, roxithromycin, azithromycin, erythromycin, tetracycline, oxytetracycline, chlortetracycline, and sulfamethoxazole in the secondary effluents were 1441.6–4917.6 ng L−1. Ofloxacin had the highest concentration. The absolute and relative abundances of total ARGs (qnrD, qnrS, ermA, ermB, tetA, tetQ, sul1, and sul2) in the secondary effluents were 103–104 copies mL−1 and 10−4–10−2 ARG/16S rRNA. Sul1 and sul2 were the major species with the highest detection frequencies and levels. In most cases, WWTP effluents were not the major contributors to the levels and species of antibiotics and ARGs in the surface water bodies. Four RWTPs removed 43.5–98.9% of antibiotics and − 0.19–2.91 log of ARGs. Antibiotics and ARGs increased in chlorination, ozonation and filtration units. Antibiotics had significantly positive correlations with ARGs, biological oxygen demands, total phosphorus, total nitrogen, and ammonia nitrogen in the four effluent-receiving water bodies. In RWTPs, the total concentrations of antibiotics showed a significant positive correlation with the total abundance of ARGs.
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•WWTP effluents were not the major contributors to antibiotics/ARGs in rivers.•Sul1, sul2 and ermB were major ARGs in the surface water bodies and WWTPs effluent.•Levels of antibiotics and ARG increased in chlorination, ozonation and filtration.•RWTPs removed 43.5–98.9% of antibiotics and -0.19–2.91 log of ARGs.•The levels of antibiotics significantly positive correlated with ARGs in RWTPs.
Water body extraction (WBE) has attracted considerable attention in the field of remote sensing image analysis. Herein, we present an enhanced deep convolutional encoder-decoder (DCED) network (or ...Deep U-Net) specifically tailored to WBE from remote sensing images by applying superpixel segmentation and conditional random fields (CRFs). First, we preclassify the entire remote sensing image into the water and nonwater areas via Deep U-Net, using the results of class membership probabilities as the unary potential in the CRF model. The pairwise potential of CRF is defined by a linear combination of Gaussian kernels, which forms a fully connected neighbor structure. Next, regional restriction is incorporated into the approach to enhance the consistency of the connected area. We use the simple linear iterative clustering algorithm to generate superpixels and correct the binary classification results by calculating their average posterior probabilities. Finally, a highly efficient approximate inference algorithm, mean-field inference, is generated for the final model. The results from the experimental application to GaoFen-2 images and WorldView-2 images demonstrate that the proposed approach exhibits competitive quantitative and qualitative performance, which effectively reduces salt-and-pepper noise and retains the edge structures of water bodies. Compared to existing state-of-the-art methods, our proposed method achieves superior final results.
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