Browsing by Author "Liu, Min"

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    Study of topographic effects on hydrological patterns and the implication on hydrological modeling and data interpolation
    (2011) Liu, Min; Bárdossy, András (Prof. Dr. rer. nat. Dr.-Ing.)
    Hydrological patterns demonstrate the spatial and temporal variability and organization of hydrological responses, and contain rich information of underlying hydrological processes. Observed patterns, or patterns interpolated properly from point data are ideal sources for distributed model input and perfect references for model calibration and validation, whereas simulated patterns can reflect the spatial land use and climate change effects and provide insight into the underlying hydrological processes. Investigation of these patterns can deepen our understanding of catchment hydrology, so that we can improve our interpolation methods and hydrological models to produce more realistic patterns for decision making in water resources management. Hydrological patterns may appear to be random, but in many cases they are highly organized and exhibit deterministic structures, which are superimposed with some random variation, because the patterns of the fundamental driving forces for the catchment evolvement - solar radiation, wind, and precipitation, are strongly related to topographic features - elevation, aspect and slope. Topographic variation exists at different scales: at large scale, earth surface features are caused mainly by geological movements and glacial carving, and referred as macro-topography in this monograph, whereas at small scale, micro-topography caused by gully incision and other secondary processes dominates. The effects of topography on catchment process may change with the scale, depending on the process. In this monograph, the direct topographic dependence of catchment processes, such as radiation, wind, drainage network, and precipitation, are referred as primary topographic effects, based on which the secondary topographic effects governing the spatial patterns of evapotranspiration (ET), soil moisture content (SMC), snow melting, soil properties, vegetation etc., can be derived. The main objective of the study is to illustrate how the topography affects these hydrological patterns at different scales through its primary and secondary effects, and how the understanding of spatial processes can advance hydrological modeling concept and practice as well as improve spatial data interpolation. To assure the generality of the research, this study applies globally available data wherever possible. The work has also exploited the three main general research methodologies in hydrology: physically-based modeling, conceptual models, and statistical analysis. Through the study of the 6 topographic dependent patterns - radiation, wind, precipitation, ET, soil moisture, and snow melting, this study delivers two important messages: first, among all the elements within a catchment, topography is the major source of variability, and this variability can be quantified to a large extent; second, pattern investigation may reveal the hidden principles of hydrological processes, is therefore key to the iterative loop of observation-understanding-modeling in hydrological study. Because for part of the study, physically justified modeling approach and globally available data are used, the methods are applicable to other areas, thus it also contributes the PUB initiation.