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Soil erosion is a severe ecological problem. Most conventional methodologies for soil-erosion assessment are appropriate for small or medium river basins. This paper presents an approach to soil-erosion intensity assessment in large basins, utilizing coded polygons identified by spatially overlapping gradation levels of primary environmental factors. Efficient assessment of soil- erosion intensity is achieved by matching the coded polygons to selected polygons pre-assigned to reference groups. A case study is presented for the soil-erosion assessment of the Yellow River Basin. It is found that the calculated and observed soil-erosion intensities are in close agreement for 86% of the total area. Sensitivity analysis indicates that acceptable results are obtained using a 5% sample of the original 9,921 coded polygons, thus reducing substantially the computational load. Direct comparisons between the polygon codes in the reference and test groups show that uncertainty is reduced with respect to previous methods. This is confirmed by the reduction in information entropy from 7.49 to 1.33. The proposed approach should be of particular use in the cost-effective assessment of soil erosion in large basins. [ABSTRACT FROM AUTHOR]

Bisphenol A is widely used for the production of epoxy resins and polycarbonate plastics, and it has been found in many wastewaters or surface waters. Adsorption of bisphenol A on sediments sampled from several representative hydrologic stations of the Yellow River was studied, and some factors that may affect the sorption of bisphenol A were analyzed using the LC-MS/MS following solid-phase extraction. The results show that neither linear nor Freundlich isotherms is fit to the experimental data due to the high carbonate content in sediments. Bisphenol A has greater adsorption after the elimination of the carbonate in the sediment, and the adsorption of bisphenol A on the treated sediment can be described by both the linear and the Freundlich isotherms. The adsorption amount of bisphenol A is related to both the total organic carbon and dissolved organic carbon of sediments. The effects of Ca2 + and K+ on the adsorption of bisphenol A were also studied. It is found that Ca2+ and K+ showed different effects on the adsorption of bisphenol A because of their different valences. [ABSTRACT FROM AUTHOR]

This paper presents a rapid forecast model for simulating hyperconcentrated sediment-laden floods in the Lower Yellow River. The model is a hybrid of a conventional one-dimensional mathematical model for unsteady sediment-laden flow and an artificial neural networks model for encapsulation of numerical results. The former provides detailed river flood routing information under typical scenarios, whereas the latter extracts modeling outputs from the former and establishes a station-specific model for efficient flood forecasting. Three typical floods that occurred in the Lower Yellow River in 1977, 1982, and 1996 are simulated. Not only the hybrid model predictions are found to be in close agreement with measured data, but also the computational speed is significantly enhanced. It is found that sediment transport is of significance with regard to the flooding behavior of hyperconcentrated flows. Therefore, the model presented herein is of particular use for rivers with high sediment concentration. [ABSTRACT FROM AUTHOR]

The ecological and environmental impacts of the Sanmenxia Hydropower Station on the lower reach of the Yellow River were examined based on the monitoring data, since the 1970s, of the Sanmenxia Hydropower Station's normal operation. Different operation modes of the reservoir were considered in addition to the effects of tributaries downstream of Sanmenxia. The environmental consequences were evaluated in terms of the total ion content (TIC), since it is regarded as the most important index reflecting the status of natural water quality in the Yellow River. However, the ecological consequence was assessed according to the severity level of the no-flow events, which has become the major concern of the Yellow River Authorities in recent years. The TIC monitored at the hydrological stations along the lower Yellow River was closely related to the reservoir's operation mode and the inflow from the tributaries between Sanmenxia and Huayuankou. Also, the variation of the severity level of the no-flow events is primarily controlled by the operation modes. The present study is of fundamental importance to determine the relative optimal operation mode of the hydropower station, so as to harmonize various purposes and constraints such as a decrease of the TIC and the severity level of the no-flow events, an increase in power generation, irrigation, and flood prevention. [ABSTRACT FROM AUTHOR]