【作者】 王多尧；

【导师】 孙保平；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2013， 博士

【摘要】 河西地区是我国著名的商品粮基地之一,石羊河流域是河西地区农业经济较为发达的区域,也是我国西北干旱区生态极为脆弱的地带,区域内生态类型多样,但是由于独特的地理环境和气候以及人类发展过程的不合理开发的逐步影响,生态环境十分脆弱,区域内地下水位下降、土地沙化、盐渍化加重、植被退化等一系列生态环境问题,土地利用变化明显。石羊河上游水源涵养林是流域内主要的水源补给区,维系着石羊河流域的生态、经济发展的战略安全,对中、下游地区的水土保持与荒漠化防治起着举足轻重的作用。因此,深入研究石羊河上游地区土地利用/森林覆被变化的水文生态响应的研究对揭示石羊河流域森林覆被变化与流域内径流的关系和区域内生态建设具有重要价值。为了进一步研究西北地区森林景观格局的变化与径流的相互关系和调控作用,本论文选择石羊河上游的中部4条河,黄羊河、杂木河、金塔河、西营河四个为研究对象,位于武威城附近汇成石羊河干流流入红崖山水库后进入民勤盆地,构成“六河”水系。应用以1999-2009年Landsat/TM的为数据源,在桌面GIS支持下利用Fragstats软件解译出研究区各景观类型,通过六个水系流域土地利用变化和降水径流变化的趋势分析,阐述土地利用/森林覆被变化和降水变化对径流过程的影响,并利用分布式水文模型SWAT模拟分析流域不同土地利用/森林覆被变化的径流变化情况,以期为石羊河上游林区森林植被建设和水资源调控提供理论依据。主要研究成果如下：(1)研究时段内石羊河上游域呈草地增加,灌木林先增后减小,针叶林、灌木林和水域面积减少的趋势；石羊河上游流域草地、农田、居民地和裸岩增加,林地和河滩地减少的趋势；在6种土地利用类型中草地所占面积最大(草地、林地、耕地、冰川与积雪、寒漠),占整个流域面积的67%以上,灌木林有明显的增加趋势,冰川与永久积雪、草地和乔木林有所减少,农田和水域增幅都在一个百分点以内,土地利用类型转化没有呈现明显的规律性。草地的变化率是最小的,为3.46%。其次为水域、森林、冰雪、灌木、农田,最大的是裸地,其中变化率达到282.64%,草地景观的稳定性最高,裸地的变化最大,是上游景观类型中最不稳定的,从斑块的格局变化来分析：裸地的景观稳定性最高,草地次之,其次,以次为灌木、冰雪、水域、森林、农田。土地利用空间转移特征为：冰川与永久积雪→裸岩、草原→耕地、灌木→草地、水域→灌木、水域→草地、水域→农田、河滩地→居民地。(2)1999-2009年石羊河上游流域出山径流量在的波动中总体呈现微弱减少趋势,就四条河流的平均情况而言,1999、2000、2001、2002年为雨水枯水期,2003、2004、2005、2006为丰水期,但到2007年以来2008-2009年径流量逐渐减少。1999-2009年以来,降水整体呈明显上升趋势,降水变化倾向率为K=-0.298,自2003中期以来,降水量增加趋势非常明显。潜在的蒸发量也在波动中呈增加趋势,变化倾向率为K=-0.2026。石羊河上游流域径流量对气候变化响应明显,降水量的变化是影响径流量变化的主要因素：全球气候变暖,导致气温升高,石羊河上游流域高寒区域冰川与冰雪融水对出山径流量具有一定稳定作用。(3) SWAT模型在石羊河上游流域的模拟高海拔山区的径流量较为准确。对率定后模拟结果进行评价得出的径流量整体相关关系数较高,整体系数高于0.80,模拟效果良好,表明SWAT模型能够比较准确的模拟高海拔山区的径流量,具有很好的实用性。(4)黄羊河流域降水量、潜在蒸发量和径流量在时间上分布不均,降雨、蒸发主要集中在7、8月份,径流在7月达到峰值。降雨对径流以及气温对潜在蒸发量都有很大的影响,气温直接影响潜在蒸发量的大小；高蒸发区主要集中在北部浅山地区,该区域太阳辐射强,降雨量少、植物覆被率低等因素有关；流域内产流量主要受降雨影响,在空间分布上与降雨分布一致。更多还原

【Abstract】 Hexi region is one of Chinese famous commodity grain bases, and the Shiyang River Basin in Hexi is a region with comparatively developed agricultural economy, as well as a region with extremely fragile ecology in the arid area of Northwest China. There are diverse ecological types within the region, but due to the unique geographical environment, climate and gradual impact of unreasonable exploitation in the process of human development, the ecological environment becomes very fragile. Worse still, a series of ecological environment problems such as groundwater recession, land sandification, aggravating salinization and vegetation degradation appear, and a change of land utilization is obvious. As the main source of water recharging in the Shiyang River Basin, forests in the upstream are key to the security of ecological and economic development in this basin and play an important role in water and soil conservation and prevention and control of desertification in the midstream and downstream basin. Therefore, in order to reveal the relations between forest coverage changes and runoff in the Basin and improve the ecological environment in the area, it has important value to do an in-depth study about the influence of land exploitation and forest coverage changes in the upper reaches of the Shiyang River on the hydrology and ecology in this area.To further study the correlation between the variation of the forest landscape pattern and the runoff in Northwest and their regulating effect, this paper selects4rivers in the central of the upstream of Shiyang River—Huangyang River, Zamu river, Jinta River, Xiying River as objects of study. The four rivers run together into Shiyang River’s main stream. After flowing into Hongya Mountain Reservoir, the stream runs into Minqin Basin, forming the hydrographic system of six rivers. The application takes Landsat/TM in1999to2009as a data source. With the support of desktop GIS, it takes advantage of the software of Fragstats to interpret every landscape types. Through analyzing the variation trend of land utilization and the runoff of rain water in the six drainage basins, it elaborates the influence of the variation of land utilization, forest coverage and precipitation to the runoff formation process. Moreover, it takes advantage of the distributed hydrological model SWAT to simulate and analyze the runoff variation according to the variations of land utilization and forest coverage, hoping to offer theoretical foundations to the construction of forest coverage and the regulation of water resource in the forest region of the upstream area. The main research achievements are as follow: (1) During the study period, there is a tendency in the upstream area of Shiyang River that the area of grassland increases, the area of shrubwood first increases and then decreases, and the area of coniferous forest, shrubwood and water decreases. The upstream area of Shiyang River has a tendency of the grassland, farmland, settlement place and bare rocks increasing while the forest and flood land decreasing. Among the six kinds of land-use types—the grassland, the woodland, the plowland, the glacier, snows and the fell-field, the grassland takes up the largest area, which is above67%of the whole drainage area The shrubwood has an obvious tendency to increase, but the glacier and snows, the grassland and the arbor frost has reduced. The growing rates of farmland and water area are within one percentage. The conversion of land utilization has not showed the evident regularity. The grassland’s rate of change is minimum, only3.46%; and the following ones are water area, forest, ice and snows, shrub and farmland. The maximum one is bare land, of which the changing rate reaches up to282.64%. The sTab.ility of grassland landscape is the highest, while the bare land changes most, turning into the least sTab.le one among the landscape types in the upstream area. Analyzing from the changing pattern of the patch, the result shows that the landscape sTab.ility of bare land is the highest, the grass ranks second. The following ones are shrubwood, ice and snows, water area, forest and farmland successively. The features of land-use space transfer is that the glacier and snows transfer to bare rocks; the grassland to plowland; the shrubwood to grassland; the water area to shrubwood, grassland and farmland; the flood land to settlement place.(2) From the general view, there was a weak decreasing trend for the runoff flowing away from mountains in the upstream area of Shiyang river basin during1999-2009. As to the average runoff of four rivers, there were drought periods in1999,2000,2001, and2002while in the year2003,2004,2005and2006there were rich precipitation. But the annual runoff slightly declined in two consecutive years (2008-2009) since2007. The precipitation showed a clear increase with the tendency rate of minus0.298(i.e. K=-0.298) from1999to2009as a whole. The rising trend is obvious since the mid of2003. The increasing trend of potential evaporation, with the tendency rate of minus2.206(i.e. K=-2.206). The runoff in the upstream of the Shiyang River gives an obvious response to climate change and the variation of runoff mainly depends on the precipitation; global warming causes the temperature to rise; the melt of the alpine glaciers and snows in the upstream of the Shiyang River basin plays a sTab.le role on the runoff flowing away from mountains.(3) In simulating the runoff of high elevation mountains on the upstream area of Shiyang River, the SWAT model is relatively accurate. According to evaluate simulating results after calibration, it proves to be that the overall correlation coefficient is relatively high, which is higher than0.8and the simulating effect is favorable. It indicates that SWAT model with its good practicability can be more accurate to simulate the runoff of high elevation mountains.(4) In the Huangyang River Basin, the precipitation, the potential evaporation and the volume of runoff are unevenly distributed in terms of time. Much rainfall and evaporation are in July and August while top runoff always comes in July. The precipitation has a significant impact on the runoff; so does the temperature on the evaporation. high evaporation is mainly in the northern low mountain range, because of the strong solar radiation, little precipitation and low forest coverage there; and the runoff is largely affected by the precipitation and shares the same spatial distribution with it.更多还原