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Abstract: The present study focuses on simulating sediment flux for 1998 big-flood with 60-year recurrent period in the Yangtze River catchment. On the basis of close correlation between discharge and sediment load recorded on the daily base of the past decades at a series of hydrological gauging stations located in the Yangtze River, the sediment rating curve of 1987/1988 was selected to simulate the annual and flood season sediment fluxes of 1998, when measured discharge was available in the most gauging stations. The result indicates that enormous sediment load was delivered downstream and to the estuary during the flood year. The simulated annual sediment flux was about 930 million-tonnes in the upper drainage basin, about 520 million-tonnes in the middle catchment and 720 million-tonnes in the lower drainage basin. These loads, respectively, approximate almost 1.9, 1.2, and 1.8 times those of the multiyearly sediment flux in the upper, middle and lower Yangtze catchments for the past decades. The result also indicates a unique pattern of sediment transport downstream through the drainage basin during the high flow season (early July to mid-September). While the upper Yangtze tributaries delivered about 580 million-tonnes of sediment downstream, the 3-Gorges valley added additional 270 million-tonnes. This totals about 850 million-tonnes that supplied the middle and lower Yangtze catchments, of which about 450 million-tonnes were silted in the middle catchments, immediately downstream of the exit of 3-Gorges. This amount is almost 6.5 times the normal flood season averaged over the last 50 years. High sediment load was also recorded in the river mouth area during the flood season, where 460 million-tonnes were delivered to the estuary and East China Sea, about 3.8 times that in a normal flood season. Intensifying human activity in the upper catchment is responsible for the large amount sediment sources delivered downstream and to the coastal region. [Copyright &y& Elsevier]

In late May and early June, 2002, a field investigation was conducted along the Three-Gorges valley of the upper Yangtze catchment by ADP (Acoustic Doppler Profile SONTEK-500). Data obtained when surveying were accompanied with discharge of <15000 m³/s in the valley and characterize the unique river-flow velocity profile and riverbed morphology. Taking into consideration the relationship between the average flow velocity and fluvial variables, four distinct river sections can be highlighted, i.e. Chongqing-Wanxian, Wanxian-Fengjie, Fengjie-Zigui and Gezhou reservoir area (upstream to downstream). The average flow velocity is in-phase with river width from Chongqing to Wanxian. High-flow velocity ranging from 3.0 to 4.0 m/s is recorded at many sites, where the wider river channel (>1000 m) and shallower water depth (<20 m) occur and large-size gravel shoals prevail. Alternated low-flow velocity (<1.5 m/s) appears at those river sections with deep water (>50 m) and U-shaped river-channel morphology. Mapping the river cross-section area at those sites can determine that smaller cross-section area accelerates the flow velocity. From Wanxian to Fengjie, the average flow velocity ranging from 3.0 to 4.5 rn/s is in-phase with the water depth. The high-flow velocity is associated with narrower river-channel, where V-shaped gorges valley occurs with small cross-section area. Further downstream from Fengjie to Zigui, the low flow velocity is linked to deep river channel characterized by W-shaped valley morphology of large cross-section area, in general. The average flow velocity is 2.5-3.5 m/s, and maximum can reach 6.0 m/s near Wu-Gorge. Our survey had also detected a slow-flow velocity (mostly <1.0 m/s) in the river channel of about 100 km long in the Gezhou reservoir downstream. Heavy siltation to 20 m thick above the former riverbed and about 20 km extending upstream from the Dam site occurs above Gezhou Dam. The backwater can reach 150 km due to elevated water level to 27 m by the damming at the end of 1970s, and riverbed erosion below the dam reaches 15-20 m. In addition, our survey records the deeper water river valley from Fengjie to Yichang, ranging from 70 to 80 m (>100 m; maximum) in the gorges valley (30-40 m below the present mean sea level). This contrasts to the relative shallow water river-channel above Fengjie, i.e. 20-30 m in general and 50-60 m, maximum at gorges site. The present ADP investigation displays the hydromorphological feature in the Three-Gorges valley, and most importantly, it accumulates invaluable dataset for the post-dam study in the near future. [ABSTRACT FROM AUTHOR]

Accurately measuring and estimating trends and variations in nutrient levels is a significant part of managing emerging eutrophic lakes in developing countries. This study developed an integrated approach containing Seasonal Trend Decomposition using Loess (STL) and a dynamic nonlinear autoregressive model with exogenous input (NARX) network to decompose and estimate the nutrient concentrations in Lake Erhai, a preliminary eutrophic lake in China. The STL decomposition results indicated that total nitrogen (TN) concentration of Lake Erhai progressively descended from 2006 to 2014, except for some agriculture area. The total phosphorus (TP) concentration showed an increasing trend from 2006 to 2013 and then decreased in 2014, but in the area near the tourist attractions, TP increased continuously from 2011 to 2014. Seasonal variations in TN and TP indicated that the lowest water quality of Lake Erhai occurred from July to October. Based on results obtained with STL, TP was selected as the sensitive parameter, as it showed a significant deterioration trend, and the area near the tourist attractions was selected as the sensitive area. Three variables (DO, pH, and water temperature) were selected as input parameters to estimate TP using the dynamic NARX model. The NARX modeling results demonstrated that it can accurately estimate TP concentrations with low root-mean-square error (0.0071 mg/L). The study establishes a new approach to better understand trends and variations in nutrient levels and to better refine estimates by identifying more easily accessible physical parameters in a preliminary eutrophic lake. [ABSTRACT FROM AUTHOR]

Abstract: An acoustic Doppler current profiler is used to characterize the river velocity against the morphology of the Yangtze River from Chonqing to the sea. High flow velocities occur in the Three Gorges section and lower velocities in the middle and lower reaches of the river. This is largely due to the change in river pattern from a high gradient deeply-cut valley to a flat fluvial plain. Flow velocities fluctuate in the middle Yangtze due to the presence of meander bends of different length. There are numerous smaller velocity fluctuations in the lower Yangtze channel that reflect multichannel pattern with numerous sand bars and a river morphology affected by bedrock outcrops. Water depths of 40–100 m occur in the Three Gorges valley but decrease to 15–40 m in the middle and lower Yangtze. At the Gezhou Reservoir, 30 km downstream of the Three Gorges damsite velocity drops to low (<1.0 m s−1) 20 km reach. A second low velocity (<0.5 m s−1) zone, about 20 km in length, is located in the lower Yangtze near the coast probably due to the tidal influence. The results from this research will serve as a datum for evaluating changes to the river once the Three Gorges dam is completed in 2009. [Copyright &y& Elsevier]

China frequently experiences natural disasters, of which flooding is the most serious. How to monitor and control natural disasters, assess damage, and provide relief is the most urgent problem for the Chinese government and disaster experts. A national integrated system using remote sensing, geographic information systems, the Global Positioning System, and other technology for monitoring and evaluating flood disasters has been assembled and tried out for 3 years. The system has played an important role in flood mitigation during the trial and has become a key part of the flood management system at China''s National Flood Control Headquarters. This paper presents an overview of the system and its use in China. [Copyright &y& Elsevier]

The molecular structure of soil organic matter (SOM) is closely related to the structure and functions of the rhizosphere community. In this study, a microcosm experiment was conducted to investigate the effect of straw-derived biochar on the structural differentiation of SOM and rhizosphere bacterial communities. 13 C NMR spectra showed that the relative abundance of carboxyl, alkyl, N-alkyl, O-alkyl and methoxyl groups decreased by 22%, 31%, 27%, 27% and 27%, respectively, and the relatively stable structure of aryl and O-aryl groups increased by 213% and 41%, respectively. In addition, network-based analysis showed that biochar amendment not only improved the network connectivity of the rhizosphere bacteria, but also enhanced the linkage between bacteria and the molecular structure of SOM. The topological properties of the network, including the number of edges, network density, and average clustering coefficient, were increased by 79%, 15% and 22%, respectively. Moreover, modularization analysis and structural equation model indicated that rhizosphere bacterial network was the important bio-factor affecting the content of labile carbon., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This paper evaluates the potential for regional bioenergy recovery as electricity and heat by small-scale methane fermentation systems from organic waste matter generated from urban, industrial, and agricultural sectors. Biogas production functions of high-strength organic wastes are derived from data of implemented methane fermentation systems. The distributions of organic wastes from sewage, household, wholesale/retail, manufacturing, farming, and livestock activities in the Tokyo Bay region are calibrated into a disaggregated spatial database by compiling general activity statistics and emission intensity parameters using Geographic Information System (GIS). Three scenarios of organic matter circulation by co-digestion in sewage treatment plants (STPs) are designed and assessed. Surplus electricity and heat from methane fermentation systems are used for STP operations and household demand. The spatial database allows a preliminary examination for the suitability of locations for technology implementation from the aspects of bioenergy supply and balance. The results show that an additional 368,000-1,328,000 MW of electricity would be generated, and 1300-3600 TJ of heat could be used by households, reducing the annual emissions of CO2 from fossil fuels by 307,000-798,000 t.

Although satellite radar altimetry was developed and optimized for open oceans, it has been used to monitor variations in the level of inland water-bodies such as lakes and rivers. Here, for the first time, we have further used the altimetry-derived variation of water level for estimating the fluctuation of water storage as an addition to the present in situ water storage estimation systems to be used in remote areas and in emergency situation such as in the events flooding monitoring and for studying the effect of climate change. Lake Dongting, the second largest lake in China, influenced frequently by flooding, was, therefore, chosen to demonstrate the potential of the technique. By using the concept of an "assumed reference point", we converted Topex/Poseidon satellite altimetry data on water level variations in Lake Dongting to "water level" data. The "water level" time-series data and in situ water storage were used to establish a rating curve. From the rating curve, we converted data on "water level" derived from seven years (1993-1999) of Topex/Poseidon data to actual water storage in Lake Dongting. The result reveals that the seasonal and annual fluctuations of water storage occurred during the 1990s with a more frequent flooding at the late 1990s' especially the flooding in whole catchment level in 1998 and 1999. The study supports the usefulness of satellite altimetry for dense and continuous monitoring of the temporal variations in water dynamic in moderate to large lakes.