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流域的水文效应是土地利用/覆被变化(LUCC)的重要环境效应之一。LUCC改变了地表植被的截流、水分入渗和地表蒸发等因素，进而对流域径流产生影响。本研究选择拉萨河流域下游地区作为研究区域，运用时间序列分析、模型模拟等方法，结合流域气候、水文和土地利用资料，深入分析了流域的土地利用/覆被变化、气候和水文变化，并利用IHACRES水文模型对土地利用/覆被变化下的流域径流进行了模拟。主要结论与创新如下： (1) 研究区土地利用/覆被现状及其动态变化特征土地利用类型的变化主要是牧草地、林地、耕地等类型之间的转变，集中在1990年代的前五年，与1991年到1995年在拉萨河谷流域实施的西藏“一江两河”中部流域地区综合开发建设等人类活动直接相关。其中增加面积最多的是林地，减少面积最多的是牧草地。 1990～1995年综合土地利用动态度在16.09%～18.43%之间，属于快速变化型，1995～2000年综合土地利用动态度较小，属于极缓慢变化型；人类活动容易影响的土地利用类型为耕地、林地、牧草地等，某类土地利用类型在局部范围内的变化幅度大于其在整个研究区整体的变化幅度。 (2) 研究区气候、水文变化特征流域气温年际变化总体呈升高趋势，尤以近20年升温最快，且冬季气温的明显升高是造成年均气温升高的主要因素。流域年降水的年际变化有一定的增加趋势，从降水十年平均值的动态变化来看，1980年代之前降水变化不大，1980年代降水最少，而1990年代降水则急剧增多。拉萨水文站径流年内分配差异较大，受降水影响多集中在夏半年（5月～10月），冬半年（11月～4月）则明显偏少；径流的年际变化表现为年均径流及月均径流（冬季的11月～2月、春季的3月～5月和夏季的7月、9月、10月）都表现出不同程度的增加趋势，尤以近20年来增加趋势更为明显。其中1970年前后为径流最可能发生突变的年份，与其它研究结论一致。流域气候（气温、降水）的变化趋势与径流变化趋势特征相似，并且不同月/年均径流受不同气候因素影响，主要表现在年平均尺度上受降水影响较大，在月平均尺度上，夏半年径流增加趋势受降水增加影响较大，而冬半年径流的增加尤其是近30年来主要受冬季气温升高的影响。 (3) 土地利用/覆被变化对径流的影响评估近些年来降水对径流的补给作用慢慢变弱，并且气温升高等因素导致冰川融水等更多的补给河流，一定程度上说明气候变化、人类活动等造成了流域下垫面状况发生改变，导致水量蒸发增大，产、汇流能力减弱，LUCC对流域的径流状况产生了一定的影响，但气候因素仍然是导致流域径流变化的主要因素。流域径流系数整体呈减小趋势，在近20年内（1980～2000年）变化剧烈，1980年代可能是受到降水量变化的影响较大，而1990年代主要受降水影响外，地表下垫面状况的改变使流域产、汇流能力发生了较大的变化，流域蒸发强烈。选用IHACRES模型并进行参数率定和检验，对流域1981～2000年土地利用/覆被变化下近20年来的径流进行模拟，结果表明： ①实测径流与模拟径流的年内变化趋势基本一致，其中大部分月份（4月～11月）实测径流小于模拟“天然径流”，主要与作物生长、人类生产生活等耗水以及LUCC一定程度上影响流域有效降水等原因有关。 ②实测径流与模拟径流的年际变化较一致，不同时期内受降水、人类用水、土地利用/覆被变化等不同因素影响，导致实测径流与模拟径流存在不同差异。土地利用/覆被变化在某种程度上对流域径流产生影响，但并非主要因素。

The hydrological impact is one of the most important environment effects aroused by the land use and land cover change (LUCC). In this thesis, the Lower Lhasa Basin was selected as the study area, and some approaches such as time-serial eigenvalue and model simulation were employed to analyse the LUCC, climate and hydrology changes. And the streamflow influenced by LUCC was also simulated with the IHACRES hydro-model. The main results and innovations are as follows: (1) The characteristics of the land use/cover actuality and its changes in the study area. It had a drainage area of 6028.8km2 in 2000, and of which the most part was the grassland (4668.3km2, 77.4%), and the next place was the wasteland (722.4km2, 12.0%), then the cultivated-land (304.3km2, 5.0%) and the timberland (254.1km2, 4.2%). The changes of the land use types were the transforms among the grassland, wasteland and cultivated land, of which the timberland had the most increasing areas, but the grassland had the most decreasing areas. The changes were concentrated in the early 5 years of the 1990s, which was correlated directly with the development construction in “One River and Two Streams” region from 1991 to 1995. The dynamic changes of the land use/cover were analysed with the approaches of the land resource change model and the regional difference model of LUCC. The results indicated that the dynamic degree of the integrated land-use was between 16.09% and 18.43% from 1990 to 1995, whose type was belongs to the rapid changing type. But the dynamic degree from 1995 to 2000 was much smaller, which was belongs to the much slowly changing type. The land use types of the grassland, cultivated-land and timberland were easily affected by human activities, and the extents of some land use types in local regions were higher than that of the whole study area. (2) The characteristics of the climate and hydrological variations in the study area. The annual mean temperature had a trend of going up with a faster increasing rate in the last 20 years, the reason of which was most the temperature increasing in winter. The annual mean precipitation showed some changing tendency which fluctuated from 300mm to 600mm. And there wasn’t a great variation in the precipitation before the 1980s, while the 1980s had a much lower precipitation, but there appeared a great increasing in precipitation in the 1990s. Influenced by the warm moist current from the Indian Ocean, the monthly mean precipitation concentrated in Jun.-Sep., which accounts for over 85% of the total. The difference of the monthly mean runoff in Lhasa hydro-station was obvious, and the runoff concentrated in the summer half-year (May.-Oct.) influenced by the precipitation. There was also a characteristic in the annual runoff variations which had an increasing trend in the annual mean, Nov.-Feb., Mar.-May. and Jul. Sep. Oct.. There had an obvious increasing trend in the last 20 years. The year 1970 was considered as the abrupt change point, which was accordance with other researchs. The tendency of the climate change (temperature and precipitation) had a similar pattern with that of the runoff change. And the climate factors which influenced runoff in different month/year were different, reflecting that the runoff was influenced most by precipitation in annual mean scale but in monthly mean scale was influenced by precipitation in summer half-year and by temperature in winter half-year. (3) The evaluation of the hydrological impacts by LUCC. The supplying function of the precipitation was decreasing with the time advancing, and the LUCC impacted the drainage surface so as to affect the streamflow indirectly, but the climate changes are the leading factors affecting the hydrological variations. The mean runoff coefficient had a decreasing trend and a most fluctuation in the last 20 years (1980-2000). The IHACRES model was selected and also had parameters calibration and inspection, and then the streamflow was simulated under LUCC impacts in the last 20 years, the results indicated that: The observed streamflow had accordance with the simulated streamflow in the monthly scale. And the observed streamflow was fewer than that of the simulated in the most months (Apr.-Nov.), the factors of which maybe the crop growth, domestic and productive water consumptions, and the impacts of LUCC indirectly leading to the effective precipitation decreasing. The annual variations of the observed streamflow had a good accordance with that of the simulated streamflow, but affected by different factors in different periods, it had a little discrepancy between the observed streamflow and the simulated. The LUCC took some impacts on the runoff in sme extent, which was not the leading factor.

摘 要..............................................................................................................................................................I
ABSTRACT...................................................................................................................................................III
第一章绪论..................................................................................................................................................... 1
第一节 选题背景和意义............................................................................................................................. 1
第二节 国内外研究进展............................................................................................................................. 1
2.1 土地利用/覆被变化对流域水文影响的机理概述........................................................................... 1
2.2 土地利用/覆被变化对流域水文效应的研究进展........................................................................... 4
2.3 拉萨河流域开展的有关研究进展及存在问题...............................................................................11
第三节 研究方案....................................................................................................................................... 12
3.1 研究目标.......................................................................................................................................... 12
3.2 研究内容.......................................................................................................................................... 12
3.3 研究方法.......................................................................................................................................... 12
3.4 技术方案.......................................................................................................................................... 13
第四节 数据来源....................................................................................................................................... 13
第二章研究区概况....................................................................................................................................... 15
第一节 研究区范围................................................................................................................................... 15
第二节 自然地理概况............................................................................................................................... 16
2.1 地形地貌.......................................................................................................................................... 16
2.2 地质与土壤...................................................................................................................................... 17
2.3 气候状况.......................................................................................................................................... 18
2.4 植被.................................................................................................................................................. 19
第三节 社会经济状况............................................................................................................................... 20
第四节 小结............................................................................................................................................... 22
第三章拉萨河流域下游地区土地利用/覆被变化分析.............................................................................. 23
第一节 土地利用数据获取及处理方法.................................................................................................... 23
1.1 数据来源.......................................................................................................................................... 23
1.2 土地利用分类系统.......................................................................................................................... 24
1.3 数据处理.......................................................................................................................................... 25
第二节 土地利用现状及其动态变化分析................................................................................................ 25
2.1 研究区土地利用现状分析.............................................................................................................. 25
2.2 研究区土地利用动态变化分析...................................................................................................... 34
第三节 小结............................................................................................................................................... 40
第四章拉萨河流域下游地区气候、水文变化特征分析........................................................................... 42
第一节 研究区近40 年来气候变化特征分析.......................................................................................... 42
1.1 气温变化.......................................................................................................................................... 42
1.2 降水变化.......................................................................................................................................... 45
第二节 研究区近40 年来水文变化分析.................................................................................................. 50
2.1 研究方法简介.................................................................................................................................. 50
2.2 拉萨站径流的变化趋势分析.......................................................................................................... 51
2.3 唐加水文站与拉萨站径流变化趋势相关分析.............................................................................. 54
第三节 径流变化的气候影响因素分析.................................................................................................... 55
第四节 小结............................................................................................................................................... 57
第五章拉萨河流域下游地区土地利用/覆被变化对径流影响评估.......................................................... 59
第一节 研究区流域面降水及流域径流的计算........................................................................................ 59
1.1 流域面降水量的计算...................................................................................................................... 59
1.2 流域径流的计算.............................................................................................................................. 60
第二节 研究区土地利用/覆被变化的水文效应分析............................................................................... 61
2.1 双累积曲线法——降水和径流的阶段变化特征.......................................................................... 61
2.2 流域径流系数的变化...................................................................................................................... 62
第三节 研究区土地利用/覆被变化下流域径流模拟............................................................................... 63
3.1 流域径流模拟理论介绍.................................................................................................................. 63
3.2 IHACRES 模型介绍........................................................................................................................ 64
3.3 模型参数率定及检验...................................................................................................................... 68
3.4 拉萨河流域下游地区土地利用/覆被变化对径流影响的定量分析............................................. 71
第四节 小结............................................................................................................................................... 74
第六章研究结论与展望............................................................................................................................... 76
第一节 主要研究结论............................................................................................................................... 76
1.1 研究区土地利用/覆被现状及其变化特征..................................................................................... 76
1.2 研究区气候、水文变化特征.......................................................................................................... 77
1.3 土地利用/覆被变化对径流的影响评估......................................................................................... 77
第二节 存在的问题................................................................................................................................... 78
2.1 土地利用/覆被变化数据问题......................................................................................................... 78
2.2 水文、气候数据问题...................................................................................................................... 78
2.3 模型模拟问题.................................................................................................................................. 79
2.4 水文效应分析.................................................................................................................................. 79
第三节 研究展望....................................................................................................................................... 79
参考文献......................................................................................................................................................... 80
个人简历......................................................................................................................................................... 87
致 谢......................................................................................................................................................... 88