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A multiobjective water resource allocation model (GWAS) was constructed to incorporate the objectives of socioeconomic water use, power generation, and river ecological flow. The new model can simulate both rule-based operating schemes and optimized operating schemes for reservoirs with two kinds of solving algorithms and was applied to the Fuhe River basin. Fifteen socioeconomic water use units, 23 ecological flow control sections in the river channel, and 22 reservoirs were considered in the case study. The advantages and disadvantages of each rule-based operating scheme and the global optimization were compared under four computational schemes with the GWAS model. The competitive relationship among socioeconomic water use, power generation, and ecological water use under empirical rules, and the global optimal operation, were revealed. The GWAS model is an improvement of the traditional water resource allocation model and enables managers to compare empirical rule-based schemes and form a better, globally-optimized scheme. [ABSTRACT FROM AUTHOR]

This study focuses on the water use characteristics and impact factors in the Yellow River basin. Water use increased from 1980 to 2000 and then stabilized. Water use in the eight regions of the basin varies significantly in both time and space. Water use in different sectors is sensitive to variations in the irrigation area, industrial added value, efficiency, population and urbanization. Change trends are the results of the joint effects of supply-and-demand relationship and water policy. Water use is insensitive to precipitation, because irrigation mainly relies on river water and groundwater. [ABSTRACT FROM AUTHOR]

Abstract With rapid urbanization, there will be more conflict between human systems and the river ecological system, and therefore, ecological operations, practices and research must involve the ecological water replenishment of entire river basins with new modeling tools. In this study, based on a water resource allocation and simulation model (WAS), we establish an ecological flow-oriented water resource allocation and simulation framework (E-WAS) by comprehensively considering both ecological flow constraints and ecological flow targets. To control multiple types of water sources and dynamically allocate water resources to replenish ecological water in the river, virtual reservoirs and ecological units are added to the model network. With new water balance equations for virtual reservoirs and ecological units, the E-WAS can simulate the ecological replenishment process in a river basin and can provide a recommended water replenishment scheme that considers optimization principles. The E-WAS was applied in the Pingshan River Basin, Shenzhen, China. Fourteen ecological units and 38 water supply nodes are considered in the model. A water replenishment scheme that used water from 6 reservoirs and reclaimed water from 5 water sewage plants was selected. This scheme significantly increased the satisfactory degree of ecological water demand and efficiently supported the formulation of a control scheme for the water environment of a basin. The E-WAS framework is similar to model plug-ins but helps to avoid the large workload that is required for model redevelopment and can expand the functions of core models relatively quickly. Graphical abstract Unlabelled Image Highlights • An expansion framework (E-WAS) is added to the water allocation model for water replenishment simulations. • An ecological flow-oriented water network can be established with virtual reservoirs and ecological units. • Water from reservoirs and reclaimed sewage facilities is used to formulate the recommended water replenishment scheme. • The degree of ecological water demand increases significantly to a satisfactory level after water replenishment. [ABSTRACT FROM AUTHOR]

Leaf area index (LAI) is a key parameter for the simulation of water and carbon cycle in many ecological and hydrological models. However, it is difficult to estimate the LAI dynamics accurately. In this work, a modified model based on the Logistic Statistical Model and the Mechanistic Model was developed to solve the problem of IBIS (Integrated Biosphere Simulator) in LAI simulation, which noted as IBIS–LAI. Comparison between the primary IBIS, IBIS–LAI, as well as Logistic Statistical Model and the Mechanistic Model are performed in Changbai Mountain broadleaved forest of China. Results show that model performance could be enhanced by modification of LAI simulation, especially in spring and autumn. The relative error of upper canopy LAI simulation by IBIS, IBIS–LAI, Logistic statistical model and mechanistic model is 86.80%, 5.39%, 8.25% and 9.53%, respectively; while the relative error of lower canopy LAI simulation is 80.01%, 18.57%, 33.63% and 20.94%. With the improvement of LAI simulation accuracy, simulation of evapotranspiration (ET), gross primary productivity (GPP) and soil temperature by IBIS–LAI has been improved. It is concluded that the modification of LAI simulation can improve the performance of IBIS on the simulation of land surface processes. [ABSTRACT FROM AUTHOR]

• The method could attribute the impact of multiple human activities. • The method could attribute on the water cycle processes not only the streamflow. • The method uses the mean of multiple scenarios estimation for one factor. • The method ensures the sum of contribution of all impact factors equals 100%. • The principle of the new method is mathematical proved. The impacts of human activities on the natural water cycle have become increasingly severe due to population growth and economic development. Therefore, it is important to evaluate the contributions of different human activities (e.g., land-use change, industrial water use, and domestic water use) on different hydrological variables. However, existing attribution methods have shortcomings when attributing the impacts of different human activities; for instance, human activities may only be considered as one impact factor, and the total impact of all factors may not be guaranteed to equal 100% of the total change. A new approach, using multiple scenario simulations from a distributed model, was developed in this study to overcome these shortcomings. All potential contributions for one impact factor were calculated by fixing the other impact factors at different statuses, and the arithmetic mean of all potential contributions was presented as the final result. This method ensures that the sum of the contributions of all impact factors equals the total change in hydrological variables between two periods, which was demonstrated mathematically. A case study of the Wei River Basin was used to evaluate the proposed methodology, which attributed four impact factors (climate change, land-use change, industrial and domestic water use, and agricultural irrigation water use) to three hydrological variables (evapotranspiration, rainfall infiltration, and streamflow drainage into the Yellow River). The results showed that the new method could attribute the impacts of the four factors to the changes of the three annual average hydrological variables between the period 1956–1980 and the period 1981–2005; these four factors accounted for 373.3%, −33.3%, −133.3%, and −106.7% of the change in evapotranspiration, 129.8%, −2.2%, −3.5%, and −24.1% of the change in rainfall infiltration, and 75.2%, 4.4%, 13.4%, and 7.0% of the change in streamflow drainage into the Yellow River, respectively. Moreover, the sum of the relative contributions of the four impact factors to the three hydrological variables was equal to 100% at an annual time scale. To avoid the limitations of existing methods, we recommend adopting the newly proposed method for evaluating the impacts of climate change and multiple human activities on water cycle processes. [ABSTRACT FROM AUTHOR]

• A sequential "slope-gully-river" structure is built in the WEP-SED. • The newly developed soil erosion model separates gully erosion process. • The gravitational erosion is simulated based on mechanical equilibrium principle. The Loess Plateau of China suffers from severe soil erosion. In the gullied rolling loess region, approximately half of the sediment derives from gully areas, which are the most prominent topographical features of this region. No existing soil erosion models are appropriate in accuracy or applicability for the Loess Plateau because existing models only consider slope and river erosion processes at the catchment scale. The absence of the gully erosion process in these models significantly limits their application to the Loess Plateau. Taking this issue into account, a three-process-based distributed soil erosion model, denoted by WEP-SED, is proposed to investigate soil erosion in this region based on the Water and Energy transfer Processes in Large river basins (WEP-L) model. In WEP-SED, a sequential "slope-gully-river" structure is built for the physically-based simulation of soil erosion and sediment yield. In this structure, soil erosion is integrated from six parts with successive transport relationships. The proposed model is applied to the upstream region of the Wenjiachuan hydrological station in the Kuye River basin. The simulated monthly average sediment transport rates from 1956 to 2010 at the Wenjiachuan hydrological station agree well with the observations, with a correlation coefficient of 0.76, an NSE of 0.58, and a relative error of −5.60%. Furthermore, the simulated average annual amount of gully erosion reaches 60.30% of the total soil erosion, reflecting the fact that the gully erosion is a serious problem and demonstrating that gully erosion must be considered separately in this area. [ABSTRACT FROM AUTHOR]

Affected by intensive human activities, basin hydrologic systems show characteristics of a dualistic structure. Thus, simulation of hydrological processes needs to consider the social water cycle system to obtain a more accurate result. This study uses a dualistic water cycle simulation system to simulate the hydrological processes affected by intensive human activities, which comprises the natural water cycle system and social water cycle system. The social water cycle system includes the agricultural water cycle system, industrial water cycle system, domestic water cycle system, and cross-regional allocation system. As part of the dualistic water cycle simulation system, an integrated dualistic hydrological model is developed which couples a distributed hydrological simulation module with a water resource allocation module. The integrated modeling approach is applied to the Haihe River basin. The results show that the model performance can be improved when considering coupled simulation of natural and social water cycle systems. This model can also be used to investigate the evolutionary relationships among the natural and social water cycle systems in the study region, and to assess the regional water resources in other basins affected by intensive human activities. [ABSTRACT FROM AUTHOR]

An analysis of the variation characteristics and evolutionary trends in the runoff of five rivers in the Poyang Lake Basin was conducted using the MK trend test, Morlet wavelet transforms, correlation analyses, and other methods. For 1956–2011, the inflow runoff displays small, statistically insignificant trends. However, for 2000–2011, significant downward trends are present. River runoff in the basin is significantly correlated with precipitation, while water intake and use is less influential; the most significant impact on river runoff is climate variability. To analyse the effects of water conservancy project scheduling and operation, we also compare the inflow and outflow runoff processes of typical large reservoirs before and after peak reservoir construction. The scheduling and operation of large reservoirs in the five rivers is known to play a supplementary role in dry season inflow runoff. The recent reduction in inflow runoff was mainly caused by basin precipitation; reasonable scheduling of water conservancy projects in the five rivers plays a positive role in safeguarding the water required by the dry season ecosystem in Poyang Lake. [ABSTRACT FROM PUBLISHER]

Hydrological processes are the driving force of transportation, transformation, and accumulation of agricultural non-point-source pollutants in a paddy irrigation district. The aim of this study was to simulate hydrological processes and non-point source pollution transport processes in a complex irrigation and drainage system in north-east China. Field experiments were conducted to measure quality and quantity of leakage and irrigation return water in field and drainage system in the Qianguo irrigation district (Jilin, China) during the period from 2009 to 2011. The hydrological processes in the various drains were different. In the field canals, the subsurface flow and leakage with high N concentrations were diluted by irrigation return water. The storage process in the lateral drains impacted the drainage process and the convection and mixing processes of the non-point pollutants significantly. In a lateral irrigation canal controlled region, the subsurface flow and the direct seepage flow from paddy fields through the side walls of field drains to the drains were simulated using unsteady flow equation. The water and contaminants in the field drains converged to lateral drains, and finally reached the main drain. A modified Muskingum method was proposed to calculate the processes of water flow and chemical transport in the drainage system. The results from the field experiments and simulations indicated that the fate of ammonium (NH4+), nitrate (NO3-), and chemical oxygen demand (COD) in the system were primarily controlled by the drainage processes. The NH4+ and NO3- transport processes were mainly affected by the surface leakage and the deep leakage process, respectively. Besides from irrigation return water, the COD mass discharged from paddy fields to drains was through both subsurface flow and deep leakage. The results clearly showed the contributions of different drainage processes to non-point source pollution in a complex drainage system during the rice-growing period. Bromide (Br-) was used as tracer to investigate water flow and solution transport in the soil during the freezing and thawing periods. The redistributions of soil water, temperature, and Br- tracer were monitored. In the frozen soil, water movement was caused by the temperature gradient, matric potential gradient and gravity. The matric potential of unfrozen water in frozen soil at an equilibrium state was estimated using a temperature-based function. A linear relationship was observed between solution flux and soil water flux. The SWAT was modified and applied successfully to simulate the drainage and contaminants (NH4+, NO3- and COD) transport processes. The methods and results from this study should be useful to characterize non-point source pollutions in paddy irrigation district of north-east China. [ABSTRACT FROM AUTHOR]

Summary: Dynamic assessment of water resources becomes desirable to reflect water resources variations in the basins under strong human impacts. A physically based distributed hydrological model, WEP-L, which couples simulations of natural hydrological processes and water use processes, is developed for the purpose. Concepts of special water resources (i.e., surface water resources and groundwater resources) and general water resources (i.e., the special water resources plus the precipitation directly utilized by ecosystem) are proposed, and an approach for dynamic assessment of water resources is suggested. Basin subdivision, classification of land covers, and deduction of water use spatial/temporal distributions in the Yellow River basin are carried out with the aid of remote sensing (RS) data and geographic information system (GIS) techniques. The basin is subdivided into 8485 sub-watersheds and 38,720 contour bands, and the WEP-L model is verified by comparing simulated and observed discharges at main gage stations. Lastly, continuous simulations of 45 years (1956–2000) in variable time steps (from 1h to 1 day) are performed for various land cover and water use conditions, and water resources assessment results under present condition of land cover and water use are compared with those under historical condition of land cover and water use. The study results reveal that: (1) the surface water resources reduced, but the groundwater resources non-overlapped with the surface water resources increased under the impact of human activities in the Yellow River basin; and (2) the special water resources reduced, but the general water resources increased accompanied with increase of the precipitation directly utilized by ecosystem in the basin. [Copyright &y& Elsevier]

Knowledge of the fate and transport of graphene (GR) nanosheets in porous media is essential to understand their environmental impacts. In this work, sand column experiments were conducted to investigate the retention and transport of surfactant-dispersed GR nanoparticles under various conditions. An anionic surfactant, sodium dodecylbenzene sulfonate (SDBS) and a cationic surfactant, cetyltrimethylammonium bromide (CTAB) were used to disperse and stabilize GR in aqueous solutions. Both surfactants were effective in stabilizing the GR particles, even at low concentration (0.004% w:v) because the surfactant coating introduced negative (SDBS) or positive (CTAB) charges on the GR surfaces. As a result, the SDBS- and CTAB-GR showed different retention and transport behaviors in the saturated porous media. At low surfactant concentration, the transport of SDBS-GR was much higher than that of the CTAB-GR, which was almost immobile in the sand columns with mass recovery rate only about 4%. When the surfactant concentration increased from 0.004% to 0.4%, it reduced the transport of SDBS-GR and dramatically enhanced the mobility of the CTAB-GR (with mass recovery rate of 91%). It is suggested that the presence of ‘free’ SDBS ions may reduce the electrosteric repulsions between SDBS-GR and sand surfaces by compressing the electrical double layer. The ‘free’ CTAB ions, however, may compete with the CTAB-GR for adsorption sites on the sand surfaces. Findings from this study indicated that the dispersion method plays an important role in affecting the environmental fate and transport of GR particles. [ABSTRACT FROM AUTHOR]

This work investigated the effects of solution pH and surface metal oxyhydroxides on the transport behaviors of carboxyl-functionalized graphene (GR) in saturated porous media. Column experiments were conducted to elucidate the transport behavior of functionalized GR in acid-cleaned and natural sand under different solution pH conditions (i.e., 5.6 and 8.3). The results showed that the functionalized GR was highly mobile in the acid-cleaned sand columns at both pH 5.6 and 8.3 with recovery rates close to 100 %. The deposition of the functionalized GR was higher in the natural sand columns, and the recovery rates were 88.4 and 96.5 % for pH 5.6 and 8.3, respectively. The reductions of the mobility of the functionalized GR in the natural sand columns could be caused by the interaction between carboxyl functional groups of the GR and the surface metal hydroxides on the sand grains, which is pH dependent. An advection–dispersion-reaction model was applied to the data and successfully simulated the transport of the functionalized GR through the acid-cleaned and natural sand columns. [ABSTRACT FROM AUTHOR]

Water resource shortages, water environmental deterioration, and water ecological degradation are becoming increasingly prominent in the Haihe River Basin under the effects of global climate change and intense human activity. Finding ways to solve these problems reasonably is an urgent task in basin water resources management. The water cycle describes the formation and transformation of every water drop, while it interacts with associated water ecology and water environment processes. Therefore, to fundamentally solve the above problems, the three processes must be combined and the evolutionary trends of the ecology and water environment driven by the water cycle must be determined. To comprehensively diagnose and solve the problems of water resources, ecology and water environment in the basin, an integrated simulation platform of the dualistic water cycle and its associated processes in the Haihe River Basin was established by fully analyzing the 'natural-social' dualistic characteristics of the evolution of the basin water cycle in this study. Accordingly, it is a supporting tool to evaluate the future trends of water resources, ecology and the water environment by setting scenarios based on the predictions of a climate mode and water control conditions. The results show that with climate change, the water consumption, groundwater overexploitation, and the amount of water flowing to the sea could develop soundly and satisfy the requirements of national economic growth in the future planning year 2030 through the implementation of water consumption control management and the South-North Water Diversion Project. Meanwhile, associated water environmental deterioration can be alleviated, and a growing trend for production capacities of the natural ecosystem and agro-ecosystem is seen. The above results provide a foundation for implementing basin water resources regulation and the most strict water resources management. [ABSTRACT FROM AUTHOR]

Highlights: [•] GO showed high stability and mobility under low ionic strength conditions. [•] Increasing ionic strength increased the retention of GO in porous media. [•] Reducing moisture content increased the retention of GO in porous media. [•] GO did not attach to the air–water interface. [•] XDLVO theory and ADR model described the experimental data well. [ABSTRACT FROM AUTHOR]