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Modeling Hydrologic Change: Statistical Methods - Chapter 6

Phát hiện đồ họa của không đồng nhất Giai đoạn chuẩn bị phân tích dữ liệu liên quan đến việc biên soạn, tổ chức sơ bộ, và xây dựng giả thuyết. Tất cả các dữ liệu vật lý, khí hậu, thủy văn có sẵn nên được biên dịch. Trong khi một biến tiêu chuẩn, chẳng hạn như xả tối đa hàng năm, thường có quan tâm chính, dữ liệu thủy văn khác có thể được nghiên cứu để quyết định có một sự thay đổi trong biến tiêu chuẩn xảy ra. Các phân tích của dòng chảy hàng ngày, khối lượng. | 6 Graphical Detection of Nonhomogeneity 6.1 INTRODUCTION The preparation phase of data analysis involves compilation preliminary organization and hypothesis formulation. All available physiographic climatic and hydrologic data should be compiled. While a criterion variable such as annual maximum discharge is often of primary interest other hydrologic data can be studied to decide whether a change in the criterion variable occurred. The analysis of daily flows flow volumes and low flow magnitudes may be useful for detecting watershed change. Physiographic data such as land use or channel changes are useful for assigning responsibility to changes and developing a method that can be used to adjust the flood record. Climatic data such as rainfall volumes reflect the extent to which the change in the annual flood series is climate related. If physiographic or climatic data do not suggest a significant watershed change it may not be necessary to apply trend tests to the flood data. The variation in the annual flood series may simply be a function of random climatic variability and this hypothesis can be evaluated by applying univariate trend tests to the sequence of data. Graphical analyses are often the first step in data analyses. They are preludes to quantitative analyses on which decisions can be based. Graphical analyses should always be considered initial steps not conclusive steps. They can be misleading when not accompanied by quantitative analyses. However failure to graph data may prevent the detection of a trend or the nature of the trend. Graphical analyses should be used in conjunction with other quantitative methods. They will be discussed in this chapter and quantitative analyses will be discussed in other chapters. 6.2 GRAPHICAL ANALYSES After compilation of data several preliminary analyses can be made in preparing to test for and if necessary adjust for the effects of watershed changes. Three general types of analyses can be made. First one or more .