【作者】 豆林；

【导师】 黄明斌；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 土壤学， 2010， 博士

【摘要】 黄河中游的黄土高原是世界上土壤侵蚀最严重的地区之一。严重的水土流失不仅使当地的生态环境恶化,也使黄河下游泥沙量增加,严重影响下游地区的生态安全。为遏制水土流失,提高降水利用效率,从上世纪50年代起,我国在黄土高原开展了大规模的水土保持工作,这些水保措施的实施减少了入黄泥沙量,同时也对河川径流产生了很大的影响。本文以黄土高原丘陵沟壑区的10条流域为研究对象,通过对比分析,研究了河川径流及其组分对水土保持措施的时间响应特征和流域间的差异性。研究结果对黄土高原生态恢复、水保设施布设、黄河水资源安全等实际问题,都有指导和借鉴意义。本研究的主要结论如下:(1)比较分析了三种自动基流分割方法PART法、滤波法、滑动最小值法在黄土高原丘陵沟壑区的适用性,从分割后基流指数的稳定性及基流过程的合理性,认为滤波法适合本区基流分割。(2)研究区内基流占总径流量的比重较大,近50年平均基流指数在37%-64%之间。受水土保持措施的影响,研究区河流基流量随时间呈明显的下降趋势,基流指数则随时间呈现出阶段性增加趋势。基流的年内分配受融雪及降雨等气候因素的影响呈现出3月、8月两个高峰。在大规模水土保持活动影响下,月基流量在各年代间表现出减少趋势,且以夏、秋季变化最为明显。(3)以芦河为例定量分析了水土保持措施对径流的影响程度。相对于治理前,芦河流域年总径流、年地表径流及年基流量分别减少60%、66%和56%,水土保持措施对芦河流域年总径流、年地表径流减少的影响比例分别为81%和89%。水土保持措施的实施削减了洪峰流量,使径流的月变化更为平稳,径流过程也趋于均匀化。(4)应用小波方法分析了黄土丘陵沟壑区河川径流的时间变化规律及其影响因素。结果表明,通过db3小波趋势分析表明,流域年降水及年总径流、地表径流、基流都有不同程度的下降趋势,径流下降趋势更明显。运用Morlet小波对流域水文序列进行多时间尺度分析,认为流域降水、总径流及径流组分都存在显著的周期性,周期集中在30-31a、21-26a、9-14a、3-4a等时间尺度附近,降水序列与径流序列主导周期的不同,径流序列的局域性周期变化特征表现出水土保持措施实施的影响。(5)受水土保持治理开始的时间、措施的空间配置、治理面积和流域下垫面等因素的影响,不同流域径流对水土保持措施的响应存在很大的差异,年总径流及地表径流的相对减少量范围分别在7%-51%、6%-50%之间。但在黄土丘陵区水土保持拦蓄的地表径流均不能对流域地下径流产生补偿效应。(6)通过分析不同流域径流系数的变化初步探讨了流域面积大小对径流效应的影响,结果表明,径流系数在不同尺度的流域上对流域面积的响应不同,受水土保持措施影响后径流系数的变化主要受治理程度的影响,与流域面积的关系不明显。更多还原

【Abstract】 The Loess Plateau in the middle reaches of the Yellow River of China is the most erosive area in the world. Severe soil erosion not only aggravates the fragile ecological environment, but also produces large amounts of sediment which deposits on the lower reaches of Yellow River, raises the riverbed, and threatens the security of that region. Since the 1950s a great number of soil conservation measures have been implemented to reduce soil erosion and increase rainfall use efficiency in the Loess Plateau. These measures are very successful and reduced sediment by 3.0×108 t yr-1 from the Loess Plateau to the Yellow River from 1970 to 1996. Meanwhile, they have resulted in great changes in streamflow regime.In this dissertation, 10 watersheds which are located in hilly and gully area of Loess Plateau were chosen as the research object. The impacts of conservation measures on runoff were analyzed from temporal and spatial scales. It could be useful to understand and evaluate the function of soil conservation measures which have been implemented, and guide the future construction of ecological resoration in this region. The main conclusions of this study are as follows:(1) Applicability of three kinds of methods, named PART, digital filter technique and smoothed minima method which all belong to automatic baseflow separations, were compared. It was concluded that the separation results of digital filtering technique was relatively stable, and the baseflow process preferable conforms to the characteristics of baseflow recession.(2)The baseflow accounted for a larger proportion of the total runoff, the average baseflow index was between 37% -64% for the 10 catchments. Strong downward trends were detected in the baseflow volumes which was affected by conservation measures, while the baseflow indices showed increasing trend in stages. Monthly baseflow displayed two peaks in March and August which were benefited from snowmelt and precipitation, and under the influence of large-scale conservation activities, decreasing trend was showed between the ages, with the most obvious changes occurring in summer and autumn.(3) Based on 50-year rainfall, runoff data of Lu River, the influence of soil and water conservation on runoff was analyzed. Compared with pre-treatment, annual runoff, surface runoff and baseflow were reduced by 60%, 66% and 56% respectively. Results showed that contribution rate of conservation measures was 81% and 89% for the annual total runoff and surface runoff changes. Conservation measures reduced the peak flow, so that the monthly change in runoff was more stable, runoff process also tended to homogenization.(4) By applying wavelet transform, the tendency and periodic variations of flow series and impact factors were studied. The standardized time series were decomposed by Multi-Resolution Analysis (MRA) using the db3 wavelet function. The reconstruction of the lowest frequency part showed the flow series descended more rapidly than precipitation. Continuous wavelet transform (CWT) was carried out to identify the periodic variation of the precipitation and flow series using the complex valued Morlet function. Results showed that all 4 series had significant periodicity which concentrated in the 30-31a, 21-26a, 9-14a, and 3-4a. But the dominant period for precipitation and flow series was different, localization of periodic variations exhibited the influence of conservation measures on runoff changes.(5) Responses of runoff to conservation measures were not consistent among 10 watersheds because of the differences in many factors, such as beginning time of soil and water conservation, spatial allocation of conservation measures, controlling area and underlying surfaces. But the similarity was that the surface runoff which were intercepted and stored by conservation measures did not compensate the amount of baseflow.(6) Through analyzing runoff coefficients changes in different catchments, impacts of catchment size on runoff effects were discussed preliminary. Results showed that the responses of runoff coefficient differed with different catchment area range. The change of runoff coefficient was mainly affected by the control degrees of soil and water conservation, its relationship with catchment size may be not significant. Keywords: Conservation measures, runoff, different scale, watersheds of the Loess Pleateau.更多还原