【作者】 齐治军；

【导师】 许明祥；

【作者基本信息】 西北农林科技大学 ， 生态学， 2010， 硕士

【摘要】 针对水土流失尺度效应研究的薄弱环节及流域水土流失预测的实际需求,通过查阅历史资料、野外调查、定位监测等方法,获取黄土丘陵区不同尺度小流域水土流失及环境要素资料,研究了黄土丘陵区不同时空尺度下小流域水土流失的基本特征及尺度效应,探讨了水土流失尺度效应的影响因素,以期为不同尺度水土流失规律尺度转换及流域水土流失评估提供依据。主要研究结论如下:1)黄土丘陵区不同尺度小流域的径流模数随着降雨量增大呈增加趋势,随着流域治理措施的实施呈下降趋势,但其变异程度较大。随着流域尺度变大,径流模数和侵蚀模数在数量和增加幅度上有变小的趋势。2)对纸坊沟和燕沟流域1997-2007年间的径流模数和侵蚀模数分析表明,黄土丘陵区实施水土保持综合治理后流域的径流模数和侵蚀模数随流域治理的实施呈下降趋势,径流模数和侵蚀模数的时间尺度效应与流域综合治理度密切相关。相对于面积较大的流域,受到降雨特征和治理的综合作用,面积较小的流域的径流模数及侵蚀模数的时间尺度效应较大。3)对黄土丘陵区不同尺度小流域研究发现,随着流域尺度的变大,流域对降雨的响应程度变小,流域的径流模数和侵蚀模数随着流域尺度增大呈下降趋势并逐步趋于稳定,但在流域尺度较小时径流模数及侵蚀模数变异较大。径流模数及侵蚀模数随流域面积变化表现出的尺度效应可以用对数函数来拟合。4)10km2和50km2是小流域径流模数和侵蚀模数尺度效应的两个转折点。在小于10km2的流域尺度内,径流模数和侵蚀模数的尺度效应较大;当流域面积大于50km2后径流模数的尺度效应明显减小。径流模数较侵蚀模数的空间尺度效应大。5)随着流域尺度的变大,径流含沙率呈下降趋势并趋于稳定;洪水持续时间随流域尺度变大而增加,但在尺度较小时变异较大。随着流域面积的增大,流域对水土流失影响因素的响应变弱,即随着流域面积的增大,流域能弱化水土流失影响因素的影响程度,表现为水土流失表征指标变异较小且趋于稳定。6)黄土丘陵区不同尺度小流域土地覆被物的空间分布存在异质性。小流域土地覆被物可划分为地表覆被物、近地覆被物及地上覆被物3种类型。不同土地覆被物的影响因素及程度也存在差异。道路及居民区侵蚀是新时期水土流失不容忽视的因素。不同庭院类型的产流产沙存在差异,相对于砖院,土质院落产流快、径流含沙率高、侵蚀模数也大。庭院的最大径流含沙率出现在产流初期。7)黄土丘陵区小流域水土流失受到降雨特征、土地覆被物、水土保持措施、土地利用、地质地形、居民区及道路等多种影响因素的综合作用。侵蚀性降雨、水土保持措施、地表覆被物等因素的空间异质性是不同面积小流域水土流失尺度效应的主要影响因素。更多还原

【Abstract】 A basic requirement in the prediction of water loss and soil erosion should take watershed scale into consideration which is insufficiently understood. The data of water loss, soil erosion and environment factors in the hilly Loess Plateau region was gained by the approaches of historical data collection, sample plot investigation and location monitoring. On this condition, the paper illustrated fundamental characteristics, watershed scale effect as well as its influence factors of water loss and soil erosion at different temporal and spatial scale. The results could provide scientific basis for the assessments of water loss and soil erosion and transition between different scales. This paper proceeded as follows:1) In the Loess Hilly region, the runoff modulus which was unstable increased with the precipitation amount, while decreased with the implementation of protective measures. Meanwhile, the runoff modulus and sediment yield rate were both appeared to have a decline trend in amount and its range along with scale enlarged.2) It was shown that runoff modulus and erosion modulus take on a decline trend after the comprehensive soil and water conservation by analyzing the observed data in Zhifanggou and Yangou watershed ranging from 1997 to 2007 in the hilly Loess Plateau. Similarly, we found that the scale effect of runoff modulus and erosion modulus had a close correlation with the degree of comprehensive soil and water conservation. Compared with larger watershed, the temporal scale effect of runoff modulus and erosion modulus in small watershed were more obvious, due to the comprehensive result of rainfall characteristic and soil and water conservation.3) The study indicated that, with increment of watershed area, the response degree of watershed to the rainfall became smaller, the runoff modulus and erosion modulus of watershed had a decline trend and tend to be stable in different small watershed in Loess hilly plateau. However, the variation of runoff modulus and erosion modulus was comparatively larger when the watershed scale was small. The scale effect of runoff and erosion modulus could be fitted by the logarithm curve with the change of watershed area.4) The small watershed with 10 km2 and 50 km2 were the two turning points of the scale effect of runoff and erosion modulus. When the watershed area was less than 10 km2, the scale effect of runoff and erosion modulus were relatively larger, while the scale effects of runoff modulus decreased obviously when the watershed area was more than 50km2. The spatial scale effect of runoff modulus was larger than erosion modulus.5) Runoff sediment ratio showed a decline trend and tended to be stable with the increase of watershed scale. The duration of flood was longer with the increment of watershed scale, and the variation was larger when the area was small. The response of watershed to the soil and water loss influencing factors became weaker. When the area increassed, the watershed could weaken the degree of effecting factors of soil and water loss. The variation, representing the soil and water loss was small and to be stable.6) The spatial distribution of land cover showed the heterogeneity in different scale small watershed in Loess hilly plateau. The land coverage could be divided in to surface coverage, near-surface coverage and above-ground coverage. The influencing factors and degree of different land coverage was not the same. The road and residential zone erosion were unneglected element in the modern soil and water loss. There was difference about runoff and sediment yield in various courtyard types. Compared with brick-courtyard, the soil-courtyard was easier to flow, and both the runoff sediment ratio and the erosion modulus are larger. The maximum of sediment ratio of courtyard occurred in the initial stage during the runoff process.7) The soil and water loss in the small watershed in the hilly Loess Plateau was the comprehensive results of rainfall characteristic, land coverage, measurement of soil and water conservation, land use, geology, resident zone and road. The spatial heterogeneity of erosive rainfall, measurement of soil and water conservation, land coverage were the main influencing factors in the scale effect of soil and water loss in the small watershed.更多还原