【作者】 冯小庆；

【导师】 严宝文；

【作者基本信息】 西北农林科技大学 ， 水文学及水资源， 2010， 硕士

【摘要】 水文系统是一个复杂的系统,水文要素的时空变化具有高度的非线性特点。运用分形理论对水文系统演化的非线性规律进行研究,可从复杂水文系统运动中发现其内在的、有序的、确定性规律,更全面地揭示水文动力系统的复杂运动特征。同时,流域径流过程变化的复杂程度,即分维数,与生态环境状况密切相关。渭河流域具有悠久的古代文明,是中华民族文明历史的摇篮,其生态环境的好坏直接关系到该区域人民生活质量的高低和流域内社会、经济的可持续发展。因此,将该区域径流分维数与生态环境联系起来,建立两者的定性定量关系,是具有理论与实践双重意义的重要课题。论文着眼于渭河流域生态环境状况的改善与生态环境建设的需要,以径流序列的分形研究为依据,运用GIS工具,通过对渭河干流水文站和两岸主要支流站年、月、旬和不同时段径流过程分维数的计算研究,建立径流过程分维数与流域生态环境状况的关系,获得评判研究区域生态环境状况的分形学量化指标,尝试建立运用支流站年径流序列特征参数结合分维数预测干流站年径流的预测模型,实现基于分形理论的河流年径流预测。经过研究,论文获得的主要结论有：(1)月径流过程具有一定的相似性,可认为其有分形特征；径流过程越复杂,相应的分维值越大；反之,分维数越大,径流过程越复杂,同样成立。(2)分维数可以用来表征径流的复杂程度。渭河流域月径流分维数最大值通常发生在8或9月,最小值则发生在2或3月。主要是由于处于汛期的8、9月份,受降雨等诸多因素的综合影响,河川径流变化大；而2、3月份基本不会有大的变动。(3)总的来说,干流站分维数变化比支流站平缓,变幅也相对小。分析其原因为,干流径流影响因素复杂,各因素的正负向抵消作用发生几率大,且对支流来水的混合与调节能力强,而支流结构简单,调节能力差。这一道理,也可解释同为支流,较大流域比小流域径流过程分维数小(4)植被覆盖率与河川径流的关系,与流域所处气候区及地形、地质、土壤等环境条件有关。不同的地形地质情况,导致植被覆盖率对径流过程的影响存在差异。通过建立渭河流域径流过程分维数与流域生态环境状况的关系,尝试获得评判研究区域生态环境状况的分形学量化指标,研究表明：在渭河流域,森林覆盖率的提高并不导致径流分维数减小；耕地面积的扩大对应径流过程分维数的增加；而林草植被覆盖率越高,其径流分维数越小。可见,林草植被覆盖率尤其是草地覆盖率可以作为评判渭河流域生态环境优劣的重要指标。即林草植被覆盖率高,生态环境优良,反之生态环境不佳。由此可知,本区实施退耕还林还草是改善生态环境状况的重要方向。(5)在分析渭河流域干支流站年径流相关关系的基础上,尝试引入一元三次多项式,以干支流站年径流分维数比值为参数,建立干支流年径流关系。结果表明,干流预测值相对实测值较小,但总体拟合效果尚可。更多还原

【Abstract】 Hydrological system is a complex system, hydrological factors of temporal and spatial variation of highly nonlinear characteristics. Fractal theory on the hydrological system evolution of nonlinear regularity, available from complex hydrological system movement found its intrinsic, ordered and deterministic laws, more fully reveal the hydrological dynamical systems complex movement, at the same time, runoff process variation of complexity is the fractal dimension and ecological environment of the closely related.Wei River Valley,with a rich ancient civilization accumulation,is the cradle of Chinese civilization and history, its ecological environment have a direct relationship with the regional people’s life quality and social, economic and sustainable development in all watershed. Therefore, establish a closely relatationship betweenn fractal dimension of regional runoff and the ecological environmentis plays a very important role in the regional developmentin both on qualitative and quantitative respects,and has a dual significance in theoritic and in practice.The papers focus on the improvement of ecological environment and it construction needs Of Wei River Valley, based on runoff series fractal, using GIS tools,calculated the fractal dimension about the year, month, ten days and different times of the process of runoff on Weihe River and the major tributaries cross.establishing a relationship between the runoff fractal dimension and the regional ecological environment state, in order to acquire the evaluation of regional ecological environment of fractal measuremen Attempt to use the annual runoff series fractal characteristics as parameters to the annual runoff forecasting model, implemented based on fractal theory of river runoff predictionAfter study, the main conclusions of the paper are:(1) Monthly discharge procedure has a certain amount of similarity, can be considered exist fractal characteristics; runoff process are more complex, the greater the fractal dimension value; on the contrary, larger the fractal dimension is, more complex runoff process.(2) The fractal dimension can be used to characterize the complexity of the runoff. Wei River basin monthly runoff fractal dimension maximum usually occurs on August or September,the minimum value is usually on February or March. Mainly because in the flood season of August and September,river runoff change greatly Influenced by rainfall; and on February and March the runoff is stable(3) In general, changes of the fractal dimension on the river station is flatter than the tributary stations, and relatively small amplitude,and the amplitude is relatively small. Analysis of the reasons are:river runoff factors are complex, runoff adjustment is ability, but the tributaries are simple in structure,poorly in adjustment. In this sense, may also interpret thar, larger tributaries’ fractal dimension are bigger than small watershed(4)The relationship between vegetational coverage and runoff, related with climate topography, geology, soils, and other environmental conditions in the watershed. Different topographic and geologic conditions,lead to effect of vegetation cover on the runoff process are different.Through establish the relationship between fractal dimension of Weihe River runoff process and the state of ecological environment, this article try to obtain fractal measurement method on evaluation of regional ecological environment,result shows:in Wei River watershed, higher forest coverage not means smaller fractal dimension,and,highter cropfield area means bigger fractal dimension and worse state of ecological environment, but highter forest-grass vegetation coverage related to the smaller runoff fractal dimension.So, forest-grass vegetation coverage could be take as important indicator to judge the state of the ecological environment in Weihe area.That is, the high the forest-grass vegetation coverage, the excellent of the eco-environmental, if on the contrary, the ecological environment is poor. From this, change more cropfield into grassland is the effective way toimprove the regional ecological environment of Weihe watershed.(5)According to analysis of the relationship between Wei River’s main basin and the tributaries, try to introduce a simple cubic polynomial with tributaries’annual runoff,take fractal dimension as parameter. Results shows that,the forecast values is not very accurate, but generally fit.更多还原