流域输沙函数应用的尺度限制

阐述了在流域产沙预测模型研究中,将试验水平范围的输沙函数的运用范围扩大,产生了数据来源的不确定性或错误的原因在于:模型不完善、重要过程的省略、初始条件的缺乏、初始条件的敏感度、异质性问题、外部动力等。数据来源的不确定性在小尺度、短时间内是能够控制的。大尺度的异质性是使得输沙函数不能仅仅建立在数量化的基础上,而应是系统历史的函数。因此,大尺度的流域产沙模型必须建立在突变量的发现及其相应的动力特征基础上,而不应是试验模型按比例放大。

Scale Limitations of Watershed Sediment Transport Formula in Application

The sources of uncertainty or error that arise in attempting to scale up the results from laboratory sediment transport studies include model imperfection,omission of important processes,lack of knowledge of initial conditions,sensitivity to initial conditions,unresolved heterogeneity and occurrence of external force.The sources of uncertainty that are unimportant or can be controlled on a small scale and over a short time may become important in the application on a large scale and over a long time.Control and repeatability,hallmarks of laboratory experiments,usually lack the large scale characteristic of large systems.Heterogeneity is an important concomitant of size,and tends to make large systems unique.Uniqueness implies that prediction cannot be based upon first-principles quantitative modeling alone,but must be a function of system history as well.In large systems,the construction of successful predictive models is likely to be based upon the discovery of emergent variables and a corresponding dynamics,rather than upon scaling up the results of well-controlled laboratory studies.