【作者】 胡宏昌；

【导师】 王根绪；

【作者基本信息】 兰州大学 ， 环境科学， 2009， 博士

【摘要】 全球变化和人类活动下的江河源区水文和能量过程成为维系江河源区作为“中华水塔”的控制要素，土地利用和气候变化对江河源区高寒生态系统的水文和水热过程平衡造成了严重的影响。本论文探讨了江河源区气候变化，分析了土地利用变化及生态系统的稳定性，利用SWAT模型研究了土地利用变化对黄河生态源区径流过程的影响。在长江源区和黄河源区分别选择典型的小流域，进行水文、能量和生态过程各环节不同时期的实验和观测，开发了一个耦合水热过程的分布式冻土水文过程模型，基于定点和模型观测数据探讨大气、土壤与植被水热传输与交换(SVAT)及流域水文过程。1．江河源区的降水整体呈现缓慢增加的趋势，降水增加量4.3mm／10年；黄河源区南区的8个站点存在降水量下降的趋势，而其他站点的降水量增加；降水变化跟海拔的关系不明显。江河源区及周边气温存在着明显增高的趋势，平均气温增幅为0.318℃／10yr，高于整个青藏高原整体的增幅水平，气温变化与海拔之间的关系不明显。作为江河源区最重要的生态系统草地，20世纪中期特别是1986年以来高覆盖草地的面积减少，生态系统稳定性减弱；而低覆盖草地的面积增加，生态系统稳定性增强。水域系统退化中，湖泊的萎缩主要发生在长江源区，而河流的萎缩主要发生在黄河源区。20世纪80年代中期以来，黄河生态源区流量减少的速度越来越快，以玛多站最为明显；同时汛期的洪峰减少速率小于基流。研究表明，LUCC对流量变化的影响平均为19％，对枯水期的影响较大，为28％左右。2．在多年冻土区，径流过程存在春汛和夏汛两个明显的汛期，春汛由降水、积雪融化和冻土活动层融化水组成，而夏汛主要由降雨组成，春末夏初(5-6月)和秋季(9-10月)的径流系数远高于年均值，有些甚至超过了1，夏季径流系数较小。通过在风火山流域的实验研究表明，SRM融雪径流模型可以成功地应用于该地区。模拟结果表明：在气温升高2℃情况下，流域积雪消融期明显提前，改变了径流在时间分布上的原有形式，整个水文过程线在时间上明显前移。在降水增加和减少10％的情况下，流域融雪径流量也随之不同程度的增加和减少，则当降水增加或者减少10％时，其峰值有较明显的变化。冻土水文模型对土壤温度的模拟的整体模型效率系数达到了0.85以上，模拟的径流的模型效率系数达到了0.731。不同气候情景下的模拟表明未来气候在温度增加1℃和降水增加10％的情境下，蒸散发增幅最大，比现在提高8.1％；温度不变，降水量减少10％，蒸散发减幅最大，比现在减少3.1％。不同植被盖度下的模拟表明，植被盖度的退化，使得蒸发量减少，径流增加，同时径流组成发生了变化，地表径流的比例增大，壤中流的比率减少。3．随着植被盖度的降低，冻结过程和融化过程变得迅速，季节冻土冻结开始时间和多年冻土活动层的融化开始时间显著提前，从而形成了季节冻土冻结深度积分增加而多年冻土活动层冻结深度积分减少两种相反的趋势。冻结期负等温线和未冻结期正等温线的最大侵入深度和持续时间随着盖度的降低而增加；但季节冻土融化期温度≥10℃等温线却随植被盖度的降低而减小，季节冻土冻结期温度≤5℃等温线对植被盖度的响应不明显。多年冻土活动层土壤剖面在40cm和120cm左右都存在着高含水层，70cm左右为低含水层；季节冻土在10cm和80cm左右为高含水层，30cm左右为低含水层。植被盖度的降低，导致多年冻土活动层土壤剖面20～60cm土壤水分减少，60～120cm土壤水分含量在除了冻结期外的三个阶段而增加；而季节冻土整个土壤剖面的水分含量随植被盖度的降低而减小。基于冻土水文模型的模拟表明，植被盖度的退化，吸收的能量减少，净辐射减少。潜热减少，地热的绝对值增加，从而促使了深层冻土的融化和活动层厚度的增加。更多还原

【Abstract】 The process of hydrology and energy under the global change and humanactivities are the control factors which retain the source region of Yangtze and Yellowriver as the "Chinese water tower". The LUCC and climate change seriously affect thebalance of hydrology and heat-water on the high-cold ecosystems of the Yangtze andYellow river. This thesis discuss the climate change and LUCC in the source region ofYangtze and Yellow river, and the influence of LUCC on streamflow in theeco-environment source region are studied by the SWAT model. Two typical smallwatershed are selected in the source region of Yangtze and Yellow river respectivelyfor the examination and observation on the process of hydrology, energy and ecologyin different stages. A SRM (snow melt runoff model) are used to discuss the responseof stream process to climate change. A frozen soil hydrology process model is built,and the heat-water process is discussed under different vegetation coverage based onmodel simulation and observation.1. The precipitation has slowly increasing trends in the whole source region ofYangtze and Yellow river, with 4.3mm every l0 years. However, the eight gaugingstation in the south region of Yellow river has a decreasing tendency, and the otherstations increase, the elevation dependency of precipitation changing is not significant.The temperature of 32 stations in and near the source region reflects significantwarming, with average warming amplitude of 0.318℃/10yr which is higher than theglobal Qinghai-Tibet Plateau. The elevation dependency of climatic warming is notsignificant.The grassland ecosystem is the most import ecosystem in the source region ofYangtze and Yellow river. The area of the high cover grassland decrease since 1950sespecially from 1986, and its ecosystem stability reduce; however, the area of the lowcover grassland increased, and its ecosystem stability increased. The degeneration oflake is mainly happened in the source region of Yangtze river, and the degeneration ofriver is mainly happened in the source region of Yellow river. The runoff gradually decreases since 1985s, and the Maduo is the most obvious.The decreased of the flood is smaller than the baseflow. The impact of the LUCC onstreamflow is about 19% over the whole year, but nearly 28% in the low water period.2. There are two obvious floods which are spring flood and summer flood in thepermafrost region. The spring flood is mainly consist by the precipitation, snowmelting and thawing water of frozen soil, while the summer flood is mainly consist bythe precipitation. The runoff coefficient in the stage of latter spring and autumn ishigher than the average and sometimes higher than 1 and the runoff coefficient inspring is much smaller.The SRM model is successfully used in the Fenghuoshan watershed. Whentemperature increase 2℃, the snowmelt season significantly shift towards earlier datesand the spatial distribution of annual runoff has also obviously been redistributedwhich present a trend of increase in spring. Increase or decrease in annual precipitationof 10% result in corresponding changes in annual runoff and peak flow.The frozen soil hydrology model simulate the process of hydrology and energy well,the model efficient coefficients of the simulated soil temperature at different depth areall over 0.85 and the streamflow is efficient coefficient is 0.731. The simulation underdifferent climate scenarios indicate that evapotranspiration is highest at the scenario oftemperature increase 1℃and the precipitation increase 10%, while it is the lowest atthe scenario of temperature unchanged and the precipitation decrease 10%. Thesimulation under different vegetation coverage reveal that with the decrease ofvegetation coverage, the evapotranspiration decrease and the runoff increase, and thenthe composition of runoff changed, with the proportion of surface runoff increased andsubrunoff decreased.3. The freeze-thaw process was sped up by the reduc-tion in vegetation cover, withthe date of onset of freez-ing for the seasonally frozen soil and of onset of thawing forthe permafrost soil being clearly earlier. With de-clining cover the integral of freezingdepth for the sea-sonally frozen soil increased, but decreased for the per-mafrost soil.The maximum invasion depth and duration of the negative isotherm for the frozenstage and of the positive isotherm for non-frozen stage increased with declining vegetation cover, however, positive isotherms (≥10℃) of seasonally frozen soil at thenon-frozen stage de-creased with declining vegetation cover, whereas the influence ofnegative isotherms (≤-5℃) for frozen soils is not obvious.There were two high soil moisture layers (0.40 and 1.20 m depths) and a lowmoisture layer (0.70 m) in the profile of the active layer of permafrost. Compara-tively,in the seasonally frozen soil the two high mois-ture layers occurred at depths of 0.10and 0.80 m, and a low moisture layer at a depth of 0.30 m. With a decline in vegetationcover, the permafrost soil moisture decreased in the top (0.2-0.60 m) of soil profile,but increased at greater depths. Comparatively, a decline in cover of the seasonallyfrozen soil resulted in a decrease in soil moisture over the entire soil profile.The simulation of the frozen soil hydrology model reveal that with the decrease ofvegetation coverage the latent heat decrease and the absolute value of ground heatincrease, which then accelerate the thawing process of the deepen frozen soil and theincrassation of the active layer.更多还原