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Due to the water resource shortage in the lower reaches of the Yellow River in recent years, this paper presents a study on water dispatching. From the view of temporal and spatial allocation of water resources) water dispatching consists of two components: reservoir regulation and water dispatching for reaches in order to implement the total volume control and coordination between users. The combined regulation model of Sanmenxia reservoir and Xiaolangdi reservoir giving full consideration to the priorities of user's water demands, conforms to the reality of the Yellow River The water-dispatching model for reaches applies various methods including the equal proportion method, weighting method, and user-involving method, which are characteristic of simplification, flexibility, and practice. In addition, the influence of flow routine time has also been considered to enable the water-dispatching scenarios obtained to be more practical The methods and models have been applied in the praxis of water dispatching in the lower reaches of Yellow River in 2000 and have resulted in significant economic and social benefits. [ABSTRACT FROM AUTHOR]

The fluvial processes are considerably complicated in the braided reach of the Lower Yellow River; and the lateral or transverse channel deformation process is especially pronounced. The state-of-the-art of simulation techniques for the channel deformation in the Lower Yellow River was analyzed in this paper, and such a conclusion was drawn that existing mathematical alluvial models only can simulate the longitudinal channel deformation and cannot simulate such the lateral deformation as lateral erosion and failure of bank. Then a new two-dimensional (2D) composite model was developed herein, consisting of a 2D flow and sediment transport submodel and a riverbank-erosion submodel. This model not only can simulate the longitudinal and lateral channel deformations, but also can be used to simulate the fluvial processes of natural alluvial rivers with complex bed morphology. Through using the proposed composite model, the flood routing and channel deformation processes during the August 1982 flood were simulated. The maximum stage along the reach and the discharge hydrograph at the outlet so obtained were in good agreement with the observed data. Simulated results of the channel deformation processes showed that during the flood season, the main channel scours and the flood plain deposits; during the dry season, the main channel deposits and banks of the floodplain retreat due to lateral erosion by the flow and failure under gravity. Such results accord with the annual varying law of bed scouring and deposition in the braided reach. [ABSTRACT FROM AUTHOR]

A series of annual natural runoff recorded at eight hydrological stations in the Yellow River basin (YRB) and distributed at the main channel and two sub-basins (Weihe basin and Fenhe basin) are studied during the period from 1951 to 1998. The trends and the beginning points (or abrupt changes) of these series are detected with Mann-Kendall test (M-K test) and its progressive application. The results show that there are similar trends for different stations. The annual natural runoff series, except for stations of Lanzhou, Hekouzhen, and Longmen, have a downward tendency at some stations whose beginning points of the trend or abrupt changes occurred in the early or mid 1990s. However, their initial years of decrease are different. The decreasing trend of runoff has led to drying-up in lower reaches of the YRB, a water resources scarcity crisis, and a deterioration of the ecosystem. The reasons for the trends have been analyzed in this paper The trends of precipitation in the corresponding regions are similar to those of annual natural runoff It is an important aspect for runoff decrease. In addition, human activities have changed the hydrological cycle and lead to a reduction in runoff to a certain degree. Finally, two countermeasures for the runoff decrease are put forward. One is to develop water savings in irrigation regions, and the other is to plan South-to-North water transfer projects for the YRB. However the conflict between supply and demand will still exist for a long time because of the water scarcity in the future. [ABSTRACT FROM AUTHOR]

A holistic approach using multiple modules is used to recommend the environmental flow for fish in the lower Yellow River. The basic steps are as follows: (1) acquire the flow-related information on selected fish in the lower Yellow River, including fish species composition, abundance and habitat use in relation to flow conditions; (2) link the selected fish to key aspects of the flow regime using a conceptual model; (3) identify the environmental flow objectives; and (4) use hydraulic and hydrologic models to determine the magnitude, duration, frequency and timing of flows required to meet these objectives. [ABSTRACT FROM AUTHOR]

Based on monitoring data of 123 meteorological stations from 1960 to 2000 near or in the Yellow River Basin, the spatial and temporal distributions and their trends for pan evaporation (PE) are investigated in this study. The results indicate that, despite the annual mean air temperature over the Yellow River Basin has, on average, increased by 0.6° over the past 40 years, the rate of PE has steadily decreased, especially in summer and spring. Compared with the period of 1960s to 1970s, the rate of annual pan evaporation during 1980s to 1990s has decreased by 126mm or 7.0 percent Spatial distribution of the rate of change show that this kind of trend is general but not universal, PE has significantly decreased over the upper and lower reaches of the Yellow River, but increased to a small degree over the middle reaches. Further analyses show that the decrease of PE is mainly related to reductions in sunshine durations and solar irradiance, owing to more clouds and aerosols. [ABSTRACT FROM AUTHOR]

Variation of δ18O, δD, and ³H in the Yellow River water were analyzed based on the isotope test results of water samples in 18 sections of the Yellow River in rainy and dry seasons. The results show the trend of the ratios of the stable isotopes increases while the ³H concentration decreases progressively from the river source to the estuary. The main factors affecting the isotopes in the river water are the mixing of foreign water bodies, evaporation, and human activities. River runoff mostly comes from the source and the middle reaches of the river. The changes of the isotopes in the river water could be served as a good indicator of the recharge of different foreign water to the Yellow River. [ABSTRACT FROM AUTHOR]