Abstract: This paper quantifies the chaos characters of annual flow time series for the Yangtze River, deals with Lyapunov exponents and their practice meaning, calcu ates the long-term correlation exponent, i. e. tractional difference exponent, and discusses the possible relation between the exponent and the value of the correlation fractal dimension. Theses nonlinear information can reveal the regularity for the annual flow time series and advance the prediction level.
Abstract: Runs of a stationary stochastic sequence follow a second-order homogeneous linear difference equation, in which, the difference equation of an independent series possesses a two fold characteristic root in terms of state generation average probabilities. The constants in the general solution can be determined by using a prior condition. Likewise, the difference equation of a dependent series has two distinct characteristic roots and the constants need to be derived from sampling data. The applicability of this method has been verified by using the drought series and the hygologic series.
Abstract: According to the theory of sediment transport mechanics, it is assumed that the movement of the soil particle on the sloping land depended on the effective shear stress of the flow which is the difference between the shear stress of the flow and the criticle shear stress of the particle on the sloping land. Therefor, a calculation formula of the soil, erosion on sloping land is deduced. And a model of the sediment yield from watershed is developed by using the soil erosion formula obtained. The new model has more physical basis of soil erosion and transport and can be used to predict the sediment yield in a flood period or in a year with less parameter which can be obtained based on the historic data. The model is verified with measured data of the Pei Jiamao catchment in the North Shanxi Province and the results are satisfactory.
Abstract: This paper analyses the coaction mechanism between scouring and armoring. Based on the research of stochastic distribution characterstics of exposing height for nonuniform sediment, the velocity profile.and the law of threshold motion, the stochastic model of scouring and armoring for riverbed is put forward. The model can calculate scour depth of riverbed and armoring steady graduation simultaneously. The testing and verifying result show that the calculating results are corresponded with observed values on the whole.
Abstract: Based on the study of nonequilibrium transportation, a one-dimentional mathematical model for fluvial erosions and deposits processes of the Lower Yellow River is formulated. Some problems, such as flow resistance, settling velocity, sediment tarring capacity and coflicient of recovery, are discussed in this paper. The different behaviour of the main channel and flood plain has taken into consideration. The results of the simulation, such as water level, roughness, thickness of erosion or deposition, size constituent of suspended load and bad load etc, are satisfied. comparing with the field data.
Abstract: This is a new way estimating large area evapotranspiration by thermal infrared satellite remote sensing data. On the basis of energe balance equation, local evapotranspiration was calculated by the difference of plant canopy and air temperature that was presented by field measuring ground surface thermal infrared tempreture and a varity of meteorological factors. Furthermore, large area evapotranspiration and distribution were estimated by thermal infrered satellite data. Study results of the way are more similar to value of field measurement, which was verified. The way will be inproved in order that it will be real applicated.
Abstract: An optimal operation model with an objective of minimizing flood peak discharge at a protected location and with a series of constrains related to water balance of reservoirs and channel routing equations is established based on the analysis of the relationship between releases of reservoirs in parallel and flood peak discharge in protected regions. The solution of the model is reached by combining recursive multistage dynamic programming with practical flood regulation rule of "releasing, storing, and diversing in succession". A case study shows the flexibility, computational efficiency, and effectiveness of the method in preventing flood peaks from reservoirs and uncontroled area from meeting together in protected region. The methodology can be adopted in real time regulating of flood and planning of flood control system.
Abstract: In Soil-Plant-Atmosphere Continuum an automated irrigation control system, based on the microgrowth and water content change of plant stem and fruit as water-requiring information, can maintain green plants a proper water deficit and adjust their microgrowth effectively. Experiment showed that, compared with the plants well irrigated, corn and orange fruit grew well when the decrease of irrigated water reached 15.6% and 21.4%, respectively.
Abstract: This paper describes systematically main results which have been obtained in nearly half a century by means of laboratory experiments, field observations, theoretical analysis and numerical modelling, in the research of generation, movement, macroscopic features and internal mechanisms of saline wedges. The author also expresses his viewpoints in the aspects of historical development, state-of-the-art, and tendencies for further exploration.