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Published By Mdpi Ag

2073-4441
Updated Tuesday, 23 November 2021

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3298
Author(s):  
Mingda Yang ◽  
Huan Liu ◽  
Yuping Han ◽  
Qinghui Zeng ◽  
Jianhua Wang ◽  
...  

The Yellow River is one of the major rivers with severe runoff declines in China, but there are significant differences in runoff changes in the upper and lower reaches of the basin and among different tributaries. However, the characteristic of runoff change and its spatial heterogeneity are not well understood in the whole basin. In this paper, 48 hydrological stations located in the mainstream and major tributaries were selected, and the meteorological and runoff data from 1956 to 2017 were collected. The multi-year and intra-year changes in runoff were analyzed, and then the attribution of climate change and human activity to runoff change was quantified by the climate elasticity coefficients. The results showed that: (1) in the past 60 years, the runoff of the Yellow River showed a serious decrease trend of −8.25 mm/10a. Moreover, most tributaries decreased significantly in runoff with a rate of −1.42 mm/10a to −28.99 mm/10a; (2) for the whole basin, the contribution of climate change and human activity to runoff changes was 13% and 87%, respectively. Moreover, the contribution of the two factors varied considerably in different tributaries. Finally, focusing on different runoff regime and socioeconomic characteristics, this study provided corresponding water resources adaptive management suggestions.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3297
Author(s):  
Xuehan Zhang ◽  
Xuwei Wang ◽  
Yeshuang Xu

The partial penetrating waterproof curtain combined with pumping wells is widely applied to deep foundation pit dewatering engineering. The filter tube of the pumping well plays a critical role on the environment effect that resulted from foundation pit dewatering. This paper investigated the impact of the filter tube on the groundwater drawdown outside the pit to provide a theoretical basis for the foundation pit dewatering design. Three patterns according to the relative position of the waterproof curtain and the filter tube, which are called wall-well patterns, namely the full-closed pattern, part-closed pattern, and none-closed pattern, have been analyzed. By taking a practice engineering case in Shanghai as an example, the relationship among the proportion of the filter tube length to the dewatering aquifer thickness, the buried depth difference of the wall-well, and the groundwater drawdown difference at both sides of the waterproof curtain are discussed by numerical simulation. The full-closed pattern is the optimal wall-well pattern on the ideal condition. The suggested and optimal values of the filter tube length to the dewatering aquifer thickness are 38.7% and 58.2%. The suggested and optimal values of the buried depth difference of the wall-well are −6.41 m and −1.92 m.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3296
Author(s):  
Fang Zhang ◽  
Han Zhang ◽  
Shaofeng Pei ◽  
Liyang Zhan ◽  
Wangwang Ye

Climate change is having a profound impact on Arctic microbiomes and their living environments. However, we have only incomplete knowledge about the seasonal and inter-annual variations observed among these microbes and about their methane regulation mechanisms with respect to glaciers, glacial melting, snow lakes and coastal marine water. This gap in our knowledge limits our understanding of the linkages between climate and environmental change. In the Arctic, there are large reservoirs of methane which are sensitive to temperature changes. If global warming intensifies, larger quantities of methane stored in deep soil and sediments will be released into the atmosphere, causing irreversible effects on the global ecosystem. Methane production is mainly mediated by microorganisms. Although we have some knowledge of microbial community structure, we know less about the methane-correlated microbes in different land types in the Svalbard archipelago, and we do not have a comprehensive grasp of the relationship between them. That is the main reason we have written this paper, in which current knowledge of microorganisms and methane-correlated types in High Arctic Svalbard is described. The problems that need to be addressed in the future are also identified.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3295
Author(s):  
Ibigoni C. Howard ◽  
Kingsley E. Okpara ◽  
Kuaanan Techato

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants that possess serious risks to human health and the environment. Forty riverbed sediments samples were collected in mangrove river bed sediments where artisanal refining of crude oil takes place in the Niger Delta of Nigeria. The concentration, occurrence, distribution, toxicity and health risk of sixteen priority PAHs (16PAHs) were analysed in the samples. Apart from Nap, Acy, BkF, InP and DbE, all the other PAHs were present in all the sampled points of the studied area with BbF and BaA recording the highest mean values. The range and mean of the total PAHs (∑16PAHs) of this study are 23.461–89.886 mg/kg and 42.607 ± 14.30 mg/kg dry weight (dw), which is classified as heavily contaminated when compared to the European classification of PAHs pollution in soil (>1.0 mg/kg). The range of the effect range factors used to assess the risk of PAHs in an ecosystem (Effect rang-low (ER-L) and Effect range-median ER-M) of this study is from 0.953 to 8.80 mg/kg. PAHs below ER-L (4.0 mg/kg) indicate no toxic effect, but values above ER-M (44.79 mg/kg) indicate toxic effects to the sediments, its resources and, ultimately, the public that consumes the resources thereof; hence, the study area falls within the contaminated category. The occurrence of the high molecular weight (HMW) PAHs (73.4%) supersedes those of the lower molecular weight (LMW) PAHs (26.6%). The diagnostic ratios and principal component analysis suggest that the main contributors of PAHS into the sediments are the combustion of biomass, fossil fuel (crude oil) and pyrogenic sources. The toxic equivalent quotient (TEQ) and mutagenic equivalent quotient (MEQ) of PAHs ranged from 2.96 to 23.26 mgTEQ/kg dw and 4.47 to 23.52 mgMEQ/kg dw, and the total mean toxic equivalency quotient (∑TEQ) (15.12 ± 8.4 mg/kg) is also greater than the safe level of 0.6 mg/kg, which indicates high toxicity potency. The mean incremental lifetime cancer risks (ILCRs) of human exposure to PAHs shows that both adults TotalILCR adults (6.15 × 10−5) and children TotalILCR children (2.48 × 10−4) can be affected by dermal contact rather than ingestion and inhalation. Based on these findings, the appropriate regulatory bodies and other organs of government in the region should enforce outright stoppage of the activities of these illegal artisans who do not have control mechanisms for loss control at the site and carry out appropriate clean-up of the area.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3293
Author(s):  
Aleksey Sidorchuk

The type of modelling of gully erosion for the projects of land management depend on the targets and degree of details of these projects, as well as on the availability of input data. The set of four models cover a broad range of possible applications. The most detailed information about predicted gullies, change of their depth, width, and volume throughout the gully lifetime is obtained with the gully erosion and thermoerosion dynamic model. The calculation requires the time series of surface runoff, catchment relief, and lithology and the complex of coefficients and parameters, some of which can be estimated only by model calibration on the measurements. The difficulty in obtaining some of these coefficients makes it necessary to use less complicated models. The stable gully model predicts final gully depths and widths and is useful for projects where only stable gully geometry is used. The modified area–slope approach is used in the two simplest models, where the position on the slopes of possible gullies is calculated without details of the gully geometry. One of these models calculates total erosion potential, taking into account all water runoff transforming a gully. The second calculates gully erosion risk, using the information about slope inclination, contributing area and maximum surface runoff.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3294
Author(s):  
Chentao He ◽  
Jiangfeng Wei ◽  
Yuanyuan Song ◽  
Jing-Jia Luo

The middle and lower reaches of the Yangtze River valley (YRV), which are among the most densely populated regions in China, are subject to frequent flooding. In this study, the predictor importance analysis model was used to sort and select predictors, and five methods (multiple linear regression (MLR), decision tree (DT), random forest (RF), backpropagation neural network (BPNN), and convolutional neural network (CNN)) were used to predict the interannual variation of summer precipitation over the middle and lower reaches of the YRV. Predictions from eight climate models were used for comparison. Of the five tested methods, RF demonstrated the best predictive skill. Starting the RF prediction in December, when its prediction skill was highest, the 70-year correlation coefficient from cross validation of average predictions was 0.473. Using the same five predictors in December 2019, the RF model successfully predicted the YRV wet anomaly in summer 2020, although it had weaker amplitude. It was found that the enhanced warm pool area in the Indian Ocean was the most important causal factor. The BPNN and CNN methods demonstrated the poorest performance. The RF, DT, and climate models all showed higher prediction skills when the predictions start in winter than in early spring, and the RF, DT, and MLR methods all showed better prediction skills than the numerical climate models. Lack of training data was a factor that limited the performance of the machine learning methods. Future studies should use deep learning methods to take full advantage of the potential of ocean, land, sea ice, and other factors for more accurate climate predictions.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3287
Author(s):  
Bushra Fatima ◽  
Basem Al Alwan ◽  
Sharf Ilahi Siddiqui ◽  
Rabia Ahmad ◽  
Mohammed Almesfer ◽  
...  

This study reports the synthesis of copper–zinc binary oxide coupled cadmium tungstate through a simple bio-precipitation method followed by calcination at 600 °C and its adsorption application. The characterization analysis reveals that the prepared composite has low particles size (nano-range), high porosity, and functional groups on the surface. The calcination of sample at 600 °C causes some essential function groups to disappear on the surface. Prepared composite was found to be effective adsorptive material to treat Congo red dye in aqueous solution. 2.5 g L−1 dose of adsorbent could remove more than 99% Congo red dye from 10 mg L−1 solution and more than 80% Congo red dye from 60 mg L−1 aqueous solution. The maximum adsorption capacity of present adsorbent was calculated to be 19.6 mg Congo red per gram of adsorbent. Isotherms analysis suggested a physio-chemical adsorption process. Thermodynamic analysis revealed a exothermic and feasible adsorption process. Adsorption rate was well explained by pseudo second order kinetics. The rate determining step was intra-particle diffusion evaluated from the Weber-Morris plot. To assess the adsorption performance of present adsorbent for Congo red dye the partition coefficient and adsorption equilibrium capacity were compared with other adsorbents. The partition coefficient and adsorption equilibrium values for 10 mg L−1 aqueous solution were found to be approximately 83.3 mg g−1 µM−1 and 4.0 mg g−1 at 30 °C and 7.0 pH using 2.5 g L−1 adsorbent. The value of partition coefficient was found to be higher than previous reported zinc oxide coupled cadmium tungstate having partition coefficient = as 21.4 mg g−1 µM−1 at 30 °C and 7.0 pH using 2.0 g L−1 adsorbent (Fatima, B.; Siddiqui, S.I.; Nirala, R.K. et al., Environ. Poll. 2021, 271, 116401). These results suggested that present adsorption technology is efficient for wastewater treatment.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3290
Author(s):  
Shuaishuai Wei ◽  
Kun Wang ◽  
Huan Zhang ◽  
Junming Zhang ◽  
Jincheng Wei ◽  
...  

Digital rock images may capture more detailed pore structure than the traditional laboratory methods. No explicit function can correlate permeability accurately for flow within the pore space. This has motivated researchers to predict permeability through the application of numerical techniques, e.g., using the finite difference method (FDM). However, in order to get better permeability calculation results, the grid refinement was needed for the traditional FDM and the accuracy of the traditional method decreased in pores with elongated cross sections. The goal of this study is to develop an improved FDM (IFDM) to calculate the permeabilities of digital rock images with complex pore space. An elliptical pore approximation method is invoked to describe the complex pore space. The permeabilities of four types of idealized porous media are calculated by IFDM. The calculated results are in sound agreement with the analytical solutions or semi-empirical solutions. What’s more, the permeabilities of the digital rock images after grid coarsening are calculated by IFDM in three orthogonal directions. These results are compared with the previously validated lattice-Boltzmann method (LBM), which indicates that the predicted permeabilities calculated by IFDM usually agree with permeabilities calculated by LBM. We conclude that the presented IFDM is suitable for complex pore space.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3288
Author(s):  
Caibian Huang ◽  
Fanjiang Zeng ◽  
Bo Zhang ◽  
Jie Xue ◽  
Shaomin Zhang

Irrigation is the main strategy deployed to improve vegetation establishment, but the effects of increasing water availability on N use strategies in desert shrub species have received little attention. Pot experiments with drought-tolerant shrub Calligonum caput-medusae supplied with water at five field capacities in the range of 30–85% were conducted using local soil at the southern margin of the Taklimakan Desert. We examined the changes in plant biomass, soil N status, and plant N traits, and addressed the relationships between them in four- and seven-month-old saplings and mature shrubs after 28 months. Results showed that the growth of C. caput-medusae was highly responsive to increased soil moisture supply, and strongly depleted the soil available inorganic N pools from 16.7 mg kg−1 to an average of 1.9 mg kg−1, although the total soil N pool increased in all treatments. Enhancement of biomass production by increasing water supply was closely linked to increasing total plant N pool, N use efficiency (NUE), N resorption efficiency (NRE), and proficiency (NRP) in four-month saplings, but that to total plant N pool, NRE, and NRP after 28 months. The well-watered plants had lower N concentrations in senesced branches compared to their counterparts experiencing the two lowest water inputs. The mature shrubs had higher NRE and NRP than saplings and the world mean levels, suggesting a higher N conservation. Structural equation models showed that NRE was largely controlled by senesced branch N concentrations, and indirectly affected by water supply, whereas NRP was mainly determined by water supply. Our results indicated that increasing water availability increased the total N uptake and N resorption from old branches to satisfy the N requirement of C. caput-medusae. The findings lay important groundwork for vegetation establishment in desert ecosystems.


Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3285
Author(s):  
Lea Piscitelli ◽  
Milica Colovic ◽  
Adel Aly ◽  
Mohamad Hamze ◽  
Mladen Todorovic ◽  
...  

Maize is a crucial global commodity, which is used not only for food, but also as an alternative crop in biogas production and as a major energy-supply ingredient in animal diets. However, climate change is jeopardizing current maize production due to its direct impact on weather instability and water availability or its indirect effects on regional climate suitability loss. Hence, new areas for sweet maize cultivation should be considered in the future. Therefore, this study focuses on the possibility of producing maize in a challenging environment in Southern Italy considering rainfed cultivation and two irrigation regimes (full and deficit). The experiment was conducted during two subsequent growing seasons under semi-arid Mediterranean climate conditions. The overall results indicated a significant difference in biomass and yield between irrigated and non-irrigated treatments, and between full and deficit irrigation. Sweet maize cultivated under deficit irrigation gained less biomass than under full irrigation and its development and fruit maturation were delayed. Under deficit irrigation, the plants gave lower yields and a higher percentage of the panicle weight consisted of kernels. Irrigation water productivity was higher for deficit than for full irrigated treatment. These findings indicate the feasibility of sweet maize production in semi-arid areas of Southern Italy using adaptive agricultural strategies including deficit irrigation and controlled water stress. Given the importance of maize production, understanding of maize growth and productivity in a challenging environment may support future agricultural programming and thereby contribute e to mitigation of the direct and indirect effects of climate change.


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