【作者】 陈鹏飞；

【导师】 陈丽华；

【作者基本信息】 北京林业大学 ， 生态环境工程， 2010， 博士

【摘要】 黄土高原是我国水土流失最严重的地区,特别是黄土丘陵沟壑区,土壤侵蚀不断加剧,恶化了区域生态环境,严重制约社会、经济的发展。本论文以黄土丘陵沟壑区典型小流域——甘肃省定西市安家沟流域作为研究对象,基于流域长期实验观测所得的气候、水文资料(1977～2008年),结合不同时期的土地利用数据(1987年、1997年和2007年),运用数理统计分析和GIS与RS空间分析等技术,以定性描述与定量分析相结合的方法,对安家沟流域降雨、土壤水、径流和泥沙等水文因子特性进行分析总结；同时,构建了适于研究流域的SWAT分布式水文模型,对流域的水沙变化与土地利用格局演变的耦合关系进行了模拟研究,进一步验证并总结了安家沟流域的水沙及土地利用格局的动态变化规律,阐析了流域水文生态过程对土地利用格局演变的响应机制,为我国黄土丘陵沟壑区优化配置水土资源和有效改善区域生态环境提供理论基础与决策依据。研究主要结论如下：(1)安家沟流域降雨是影响流域水沙变化的主要因素,流域降雨时空分布的不均匀性是十分显著的,且暴雨导致该流域严重的水土流失。各类型暴雨发生的次数与年降水的多少有一定相关性,但以年降雨量的多少直接判断暴雨发生频率的高低,以及产流产沙的多少,不科学,有偏差。(2)安家沟流域内,降水几乎是其土壤水分的唯一来源,流域年降雨量对年土壤含水量均值有直接的影响,降雨量越大,土壤含水量也就越高。不同土地利用类型的土壤水分年内循环过程均为“水分补偿-水分消耗-水分补偿”。不同土地利用类型的土壤含水量垂直变化有差异,但都以地表0-40cm范围内的水分分布变化最大,且水分变幅随土层深度增加而变小是剖面水分分布的共同特征。从调节土壤水分功能来看,林地调节能力要比耕地和草地的强：同时,不同土地利用类型土壤水分平衡分析结果也表明,林地的蒸散耗水量较大,而地表径流量相对最少。在安家沟流域灌乔木林地能有效地拦蓄径流,增加降雨入渗量,起到保蓄水土、减少水土流失的重要作用。(3)在黄土丘陵沟壑区,不同土地利用类型改变了坡地水分和泥沙的贮存状况,研究的5种土地利用类型坡地的单位面积年产流量之间及单位面积年产沙量之间都存在显著差异,但它们年尺度上均值大小变化趋势一致,都符合“坡耕地(小麦)>人工草地(苜蓿)>乔木林地(油松)>自然草地(针茅)>灌木林地(沙棘)”的规律；相同土地利用类型条件下,在研究的坡度范围内(10°～20°),坡地单位面积年产流和产沙量都随着坡度的升高而增大,其中不同坡度坡地单位面积年产流无显著差异,但单位面积年产沙差异显著。(4)流域各土地利用类型都不同程度的受到人为干扰,其土地利用变化的主要特色是梯田和林地面积的增加,主要来源是坡耕地转化和荒坡开垦；1997～2007年内梯田、坡耕地和草地的变化速度均快于1987～1997年内的；但流域各土地利用斑块类型在景观中呈均衡化趋势分布。(5) SWAT模型应用于安家沟流域时,径流模拟效果好于泥沙,年际尺度模拟计算结果比月尺度理想,其次是丰水季节各月的径流模拟,再次是泥沙月尺度模拟。SWAT模型数值模拟结果表明：产流量方面,流域不同土地利用类型的单位面积的年均产流量的大小依次是,耕地>未利用地>草地>有林地>其他用地(建设用地为主)；产沙量方面,流域不同土地利用类型的单位面积的年均产沙量的大小依次是,未利用地>耕地>草地>其他用地>有林地。(6)建立情景数值模型,采用固定一个因子(气候或土地利用变化)的方法,定量分析了安家沟流域土地利用格局演变对水沙变化的影响程度。随着林草覆盖率增加,流域的产流产沙随之减少,水沙的变化响应强烈程度先强后弱,即当流域林草覆盖率达到一定值时,其对流域径流泥沙的调节作用将减小。林草地具有很明显的减水减沙的生态水文功能,且对产沙的影响大于对产流的影响。更多还原

【Abstract】 The Loess Plateau is a region where water and soil erosion is the most serious in china, especially, soil erosion is worsening and the regional ecological environment is deteriorating in loess hilly-gully region, which seriously hampered the harmonious development of social economy. Anjiagou watershed in Dingxi city of Gansu province was selected as research object in this thesis. Based on systemic hydrological and meteorological observation(1977～2008), and the information data of land use of 1987, 1997 and 2007, and relied on mathematical statistic and spatial analysis technology of GIS&Rs and so on, by the method of combining of qualitative description and quantitative analysis, the characteristics of hydrological factors such as rainfall, soil moisture, runoff and sediment in Anjiagou watershed were analyzed and summarized; Meanwhile, a suitable distributed hydrological model SWAT was constructed, that was used to simulate and study the coupling between variation of water and sediment and evolution of land use pattern, the dynamic variation law of water and sediment and land use pattern in Anjiagou watershed was further verified and summarized, and response mechanism that eco-hydrological processes on evolution of land use pattern was interpretated, that can provide theoretical foundation and decision basis for collocating optimally water and soil resources and improving the regional ecological environment of loess hilly-gully region in china.The main conclusions of this thesis were listed as following:(1)Rainfall was the main factors affecting variation of runoff and sediment in Anjiagou watershed, spatial and temporal distribution of rainfall was significant uneven. There was correlation between frequency of occurrence of different type rainstorm and yearly precipitation in watershed, but it was unscientific and biased that the level of storm frequency and the amount of runoff and sediment was directly determined by the amount of annual rainfall.(2)Annual rainfall impacted directly mean annual soil moisture content in Anjiagou watershed, precipitation was almost the only source of soil moisture, it was more, and soil moisture is greater. Soil moisture cycle of different land use types was "water compensation-water consumption-water compensation". There were differences in the vertical variation of soil moisture content of different land use types, and the greatest variation of soil moisture content distribution was in 0-40cm range of soil layer, it was a common feature of the profile distribution of soil moisture that amplitude of variation of soil moisture becomed smaller with the increase of soil layer depth. View from the function of regulate soil moisture, forest land was stronger than farmland and grassland. Water balance analysis of different land use types also showed that:Evapotranspiration of forest land was larger, its surface runoff was less relatively. So forest land can store runoff and increase infiltration of rainfall effectively, it was an important role in reducing soil erosion and storaging soil and water in Anjiagou watershed.(3)In loess hilly-gully region, situation of storage of water and sediment in slope land were changed by different land use types, there was a significant difference among annual runoff per unit area of five kinds of land use types slope lands, and it was same as annual sediment yield per unit area, but their mean trends in years were consistent, and were in accordance with the laws of "sloping farmland (Triticum aestivum L. cv Leguan)＞artificial grassland (Medicago sativa L.)＞arbor land (Pinus tabuliformis Carr.)＞natural grassland (Stipa bungeana Trin.)＞shrub land(Hippophae rhamnoides L.)"; under same land use type condition, annual runoff per unit area and annual sediment yield per unit area of slope lands were increased along with rising of the slope in research scale (10°～20°), and about slope lands of different slope degrees, there was no significant difference among annual runoff per unit area, but a significant difference existed among annual sediment yield per unit area.(4)A11 of land use types in Anjiagou watershed was disturbed by human in different degrees, the main feature of land use change was the area of forest land and terraced field were obviously increased, and farmland conversion and wasteland reclamation were their main source; the rate of transformation of terraced fields, sloped farmland and grassland were faster in 1997 to 2007 than that in 1987 to 1997, but various land use types in the landscape patch was balanced distribution trend in Anjiagou watershed.(5)According to the simulated results by SWAT model on Anjiagou watershed of yearly step, the simulated mean annually runoff had the best veracity, the veracity of simulated value in yearly step was better than that in monthly step. The veracity of monthly simulated value in rainy season was better than that in dry season, the simulated mean monthly sediment had not good veracity. SWAT model simulation results indicated:about runoff, the order of verage annual runoff per unit area of five kinds of land use types was cultivated land＞unused land＞grass land＞forest land＞other land(construction Land); about sediment, the order of verage annual sediment per unit area of five kinds of land use types was unused land＞cultivated land＞grass land＞other land＞forest land.(6)Numerical model scenarios were set up by using the method of fixed a factor(climate or land-use change), impact of evolution of land use pattern to variation of runoff and sediment were analyzed quantitativly. With the increase of vegetation cover, runoff and sediment in watershed were reduced, intensity of their variation response to change of vegetation cover were first strong and then weak, that is, when vegetation cover in watershed reached a certain value, its regulating effect to runoff and sediment would be reduced. Obviously, the ecological and hydrological functions of forest land and grass land were making runoff and sediment reduce, and the impact on sediment was greater than the impact on the runoff.更多还原