Nanjing Hydraulics Research Institute

China

Nanjing Hydraulics Research Institute

China

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Shi W.,Nanjing Hydraulics Research Institute | Zhu L.,Chinese Academy of Sciences | Chen Q.,Nanjing Hydraulics Research Institute | Lu J.,Huaneng Lancang River Hydropower Co. | And 3 more authors.
Bioresource Technology | Year: 2017

Microalgae are often used as feedstock for renewable biofuel production and as pollutant up-takers for wastewater treatment; however, biomass harvesting still remains a challenge in field applications. In this study, electro-flocculation using aluminium electrolysis was tested as a method to collect Chlorella vulgaris. The electrolysis products were positively charged over a wide pH range below 9.5, which gave them a flocculation potential for negatively charged microalgae. As flocculants were in-situ generated and gradually released, microalgae flocs formed in a snowballing mode, resulting in the compaction of large flocs. When higher current density was applied, microalgae could be harvested more rapidly, although there was a trade-off between a higher energy use and more residual aluminium in the culture medium. Benefits of this flocculation method are twofold: the phosphate decrease in post-harvesting could improve nutrient removal in microalgae based wastewater treatment, while the ammonium increase may favor microalgae recovery for medium recycling. © 2017 Elsevier Ltd


Nazari Samani A.,University of Tehran | Chen Q.,Nanjing Hydraulics Research Institute | Chen Q.,Chinese Academy of Sciences | Khalighi S.,University of Tehran | And 3 more authors.
Hydrology and Earth System Sciences | Year: 2016

A gully as an accelerated erosion process is responsible for land degradation under various environmental conditions and has been known as a threshold phenomenon. Although the effects of gullying processes have been well documented, few soil erosion models have taken into account the threshold condition necessary for gully development. This research was devoted to determining the effects of land use change on hydraulic threshold condition and stream power of water flow through an in situ experimental flume (15m × 0.4 m). Results indicated that head cut initiation and detachment rates showed a better correlation to stream power indices than shear stress (τcr). The threshold unit stream power value (ωu) for head cut initiation in rangeland, abandoned land, and dry farming land was 0.0276, 0.0149, and 4.5 × 10-5 ms-1, respectively. Moreover, the micro-relief condition of soil surface and surface vegetation affected the flow regime of discharge and velocity. It is seen that the composite hydraulic criteria of Froude number (Fr) and discharge (Q) can clearly discriminate the land uses' threshold. In fact, the remarkable decrease of τcr in dry farming was related to the effect of tillage practice on soil susceptibility and aggregate strength. The findings indicated that using the unit steam power index instead of critical shear stress could increase the models' precision for prediction of head cut development. Compared to the Ephemeral Gully Erosion Model (EGEM) equation for critical shear stress, it is important to point out that for modelling of gully erosion, using single soil attributes can lead to an inaccurate estimation for τcr. In addition, based on the findings of this research, the use of threshold values of τcr = 35 dyne cm-2 and ωu=0.4 cm s-1 in physically based soil erosion models is susceptible to high uncertainty when assessing gully erosion. © 2016 Author(s).


Chen Q.,Chinese Academy of Sciences | Chen Q.,Nanjing Hydraulics Research Institute | Zhang C.,Chinese Academy of Sciences | Recknagel F.,University of Adelaide | And 2 more authors.
Ecological Modelling | Year: 2014

SALMO (Simulation by means of an Analytical Lake Model) describes the seasonal dynamics of PO4-P, NO3-N, detritus, chlorophyta, bacillariophyta, cyanophyta and cladocerans of the epilimnion and hypolimnion of stratified lakes by complex ordinary differential equations. This study adapted the model for shallow polymictic lakes and developed a real-coded genetic algorithm to optimize key parameters identified by sensitivity analysis. Meiliang Bay of Taihu Lake is taken as a study case, and 5 years data were collected for model calibration and validation. Given the good performance of the adapted and optimized SALMO, the model was applied to analyze four management scenarios for the Meiliang Bay, including 50% reduction of external nutrient loads, 50% reduction of internal nutrient loads, 50% reduction of zooplankton mortality and 1°C increase of water temperature. The study showed: the adapted SALMO model is applicable to shallow polymictic and hypertrophic lakes; the real-coded genetic algorithm significantly improved the model efficiency and accuracy; reduction of nutrients from sediment release appears to be a key measure for controlling cyanobacteria blooms in Lake Taihu; biomanipulation is very delicate and can only be implemented with sufficient investigation and great caution; the increase of algae biomass due to water temperature rise indicates extra potential threat from climate change to lake ecosystems. © 2013 Elsevier B.V.


Liu X.,Chinese Academy of Sciences | Liu X.,Hunan Agricultural University | Chen Q.,Chinese Academy of Sciences | Chen Q.,Nanjing Hydraulics Research Institute | Zeng Z.,CAS Institute of Subtropical Agriculture
Water Science and Technology | Year: 2014

Different crops can generate different non-point source (NPS) loads because of their spatial topography heterogeneity and variable fertilization application rates. The objective of this study was to assess nitrogen NPS load reduction efficiency by spatially adjusting crop plantings as an agricultural conservation management (ACM) measure in a typical small agricultural watershed in the black soil region in northeast China. The assessment was undertaken using the Soil and Water Assessment Tool (SWAT). Results showed that lowland crops produce higher nitrogen NPS loads than those in highlands. It was also found that corn gave a comparatively larger NPS load than soybeans due to its larger fertilization demand. The ACM assessed was the conversion of lowland corn crops into soybean crops and highland soybean crops into corn crops. The verified SWAT model was used to evaluate the impact of the ACM action on nitrogen loads. The results revealed that the ACM could reduce NO3-N and total nitrogen loads by 9.5 and 10.7%, respectively, without changing the area of crops. Spatially optimized regulation of crop planting according to fertilizer demand and geological landscapes can effectively decrease NPS nitrogen exports from agricultural watersheds. © IWA Publishing 2014.


Chen Q.,Chinese Academy of Sciences | Chen Q.,Nanjing Hydraulics Research Institute | Chen Q.,China Three Gorges University | Rui H.,Chinese Academy of Sciences | And 2 more authors.
Science of the Total Environment | Year: 2014

Algal blooms are a serious problem in waters, which damage aquatic ecosystems and threaten drinking water safety. However, the outbreak mechanism of algal blooms is very complex with great uncertainty, especially for large water bodies where environmental conditions have obvious variation in both space and time. This study developed an innovative method which integrated a self-organizing map (SOM) and fuzzy information diffusion theory to comprehensively analyze algal bloom risks with uncertainties. The Lake Taihu was taken as study case and the long-term (2004-2010) on-site monitoring data were used. The results showed that algal blooms in Taihu Lake were classified into four categories and exhibited obvious spatial-temporal patterns. The lake was mainly characterized by moderate bloom but had high uncertainty, whereas severe blooms with low uncertainty were observed in the northwest part of the lake. The study gives insight on the spatial-temporal dynamics of algal blooms, and should help government and decision-makers outline policies and practices on bloom monitoring and prevention. The developed method provides a promising approach to estimate algal bloom risks under uncertainties. © 2014 Elsevier B.V.


Zhang X.,Nanjing Hydraulics Research Institute | Dou X.,Nanjing Hydraulics Research Institute | Zhang J.,Nanjing Hydraulics Research Institute
Proceedings of the Coastal Engineering Conference | Year: 2012

The author establishes the Yangtze estuary 2D tidal and sediment mathematical model based on the orthogonal curvilinear coordinate system. The erosion and siltation of engineering section under the hydrological conditions of flood season, dry season and the great flood after the Baimao Sand control engineering is calculated. Preliminarily expounds the correlation of Baimao Sand and Biandan Sand and the impact of Biandan Sand after the Baimao Sand control engineering is implemented.


Xu Q.,CAS Research Center for Eco Environmental Sciences | Liu R.,CAS Research Center for Eco Environmental Sciences | Chen Q.,CAS Research Center for Eco Environmental Sciences | Chen Q.,Nanjing Hydraulics Research Institute | And 2 more authors.
Journal of Environmental Sciences (China) | Year: 2014

Water supply is the primary element of an urban system. Due to rapid urbanization and water scarcity, maintaining a stable and safe water supply has become a challenge to many cities, whereas a large amount of water is lost from the pipes of distribution systems. Water leakage is not only a waste of water resources, but also incurs great socio-economic costs. This article presents a comprehensive review on the potential water leakage control approaches and specifically discusses the benefits of each to environmental conservation. It is concluded that water leakage could be further reduced by improving leakage detection capability through a combination of predictive modeling and monitoring instruments, optimizing pipe maintenance strategy, and developing an instant pressure regulation system. The environment could benefit from these actions because of water savings and the reduction of energy consumption as well as greenhouse gas emissions. © 2014 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.


Dou X.,Nanjing Hydraulics Research Institute | Zhang X.,Nanjing Hydraulics Research Institute | Wang X.,Nanjing Hydraulics Research Institute | Wang J.,Nanjing Hydraulics Research Institute
Proceedings of the Coastal Engineering Conference | Year: 2012

In order to resist tides and salt intrusion, there have been more than 300 tidal gates built at many river estuaries in China since 1960s. However, the serious deposition occurred at a lot of gates due to the changes of hydrodynamic and sediment conditions and lack of discharge from the rivers. At present, the research is mainly to analyze the reasons for siltation downstream gates and the measures of dredging. It is not enough for study on distribution simulation of deposition downstream sluice. Studies have shown that 2D numerical model cannot reflect the distribution of sediment siltation downstream gates. Therefore, it needs to develop 3D sediment numerical model for deposition prediction. In this paper, combined the feasibility study of a tidal gate at Mulanxi River, a physical model and 3D numerical model of sediment siltation downstream gate are conducted.


Han J.-C.,Tsinghua University | Huang G.,University of Regina | Huang Y.,Tsinghua University | Zhang H.,Texas A&M University-Corpus Christi | And 2 more authors.
Science of the Total Environment | Year: 2015

Lack of hydrologic process representation at the short time-scale would lead to inadequate simulations in distributed hydrological modeling. Especially for complex mountainous watersheds, surface runoff simulations are significantly affected by the overland flow generation, which is closely related to the rainfall characteristics at a sub-time step. In this paper, the sub-daily variability of rainfall intensity was considered using a probability distribution, and a chance-constrained overland flow modeling approach was proposed to capture the generation of overland flow within conceptual distributed hydrologic simulations. The integrated modeling procedures were further demonstrated through a watershed of China Three Gorges Reservoir area, leading to an improved SLURP-TGR hydrologic model based on SLURP. Combined with rainfall thresholds determined to distinguish various magnitudes of daily rainfall totals, three levels of significance were simultaneously employed to examine the hydrologic-response simulation. Results showed that SLURP-TGR could enhance the model performance, and the deviation of runoff simulations was effectively controlled. However, rainfall thresholds were so crucial for reflecting the scaling effect of rainfall intensity that optimal levels of significance and rainfall threshold were 0.05 and 10. mm, respectively. As for the Xiangxi River watershed, the main runoff contribution came from interflow of the fast store. Although slight differences of overland flow simulations between SLURP and SLURP-TGR were derived, SLURP-TGR was found to help improve the simulation of peak flows, and would improve the overall modeling efficiency through adjusting runoff component simulations. Consequently, the developed modeling approach favors efficient representation of hydrological processes and would be expected to have a potential for wide applications. © 2015 Elsevier B.V.


PubMed | Tsinghua University, University of Regina, Texas A&M University-Corpus Christi and Nanjing Hydraulics Research Institute
Type: | Journal: The Science of the total environment | Year: 2015

Lack of hydrologic process representation at the short time-scale would lead to inadequate simulations in distributed hydrological modeling. Especially for complex mountainous watersheds, surface runoff simulations are significantly affected by the overland flow generation, which is closely related to the rainfall characteristics at a sub-time step. In this paper, the sub-daily variability of rainfall intensity was considered using a probability distribution, and a chance-constrained overland flow modeling approach was proposed to capture the generation of overland flow within conceptual distributed hydrologic simulations. The integrated modeling procedures were further demonstrated through a watershed of China Three Gorges Reservoir area, leading to an improved SLURP-TGR hydrologic model based on SLURP. Combined with rainfall thresholds determined to distinguish various magnitudes of daily rainfall totals, three levels of significance were simultaneously employed to examine the hydrologic-response simulation. Results showed that SLURP-TGR could enhance the model performance, and the deviation of runoff simulations was effectively controlled. However, rainfall thresholds were so crucial for reflecting the scaling effect of rainfall intensity that optimal levels of significance and rainfall threshold were 0.05 and 10 mm, respectively. As for the Xiangxi River watershed, the main runoff contribution came from interflow of the fast store. Although slight differences of overland flow simulations between SLURP and SLURP-TGR were derived, SLURP-TGR was found to help improve the simulation of peak flows, and would improve the overall modeling efficiency through adjusting runoff component simulations. Consequently, the developed modeling approach favors efficient representation of hydrological processes and would be expected to have a potential for wide applications.

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