【作者】 胡光成；

【导师】 万力； 金晓媚；

【作者基本信息】 中国地质大学（北京） ， 地下水科学与工程， 2010， 博士

【摘要】 银川平原作为宁夏乃至西北地区珍贵的人工生态绿洲,其规模和稳定性取决于区域水资源量。近年来,由于黄河断流,宁夏黄河引水量逐渐减少。水资源的不合理利用加剧了银川平原生态环境的恶化,造成主要环境因素组合不协调,自然生态系统功能偏低,环境容量较小,生态平衡脆弱。地表蒸散发作为区域水量平衡和能量平衡的主要成分,不仅在水循环和能量循环过程中具有极其重要的作用,也是生态过程与水文过程的重要纽带。通过对银川平原地表蒸散发在时空演化及其影响因素方面的研究,加深对绿洲内部水循环过程的认识,可以为银川平原水资源合理开发利用、水土资源合理配置及生态环境保护等提供决策支持。利用获取到的晴空无云的MODIS数据及遥感定量反演模型SEBS(Surface Energy Balance System)估算了银川平原的地表蒸发量,推算了未获取到卫星遥感图像的日蒸发量,并对其推算误差进行了定量评估,结果表明:(1)银川平原2004年的蒸发量约为38.16×108 m3。(2)银川平原地表蒸发量在7月上旬至8月中旬达到最大值,约为3 mm/d;11月中旬至12月以及1月份,地表蒸发量最小,不足0.5 mm/d。通过地表蒸发量、土地覆盖类型、地下水位埋深及NDVI进行空间叠加与GIS复合分析,合理地揭示了银川平原地表蒸发量的空间分布特征及其与地下水位埋深及植被覆盖之间的关系,在此基础上获得了不同植被覆盖条件下的潜水蒸发极限埋深:(1)银川平原中的不同土地覆盖类型,其地表蒸发量之间具有明显的差异性,蒸发量由大到小依次是:水体、耕地、密集灌丛、草地、城市和建设用地、稀疏灌丛、裸地。(2)在枯水期,银川平原地表蒸发量的空间分布主要受地下水位埋深的影响;水位埋深小于1.6 m的地区由于土壤次生盐渍化的发育,地表蒸发量较小;地下水位埋深在1.6– 2.2 m时,蒸发量达到最大值,之后随埋深的增大而减小,并在埋深达到4 m时趋向一稳定值,因此银川平原枯水期裸土的潜水蒸发极限埋深约为4 m。(3)在丰水期,银川平原地表蒸发量的空间分布主要受植被覆盖及地下水位埋深的影响;地表蒸发量随地下水位埋深的增大而减小,在埋深达到6 m时趋向一稳定值,因此银川平原丰水期存在植被覆盖时的潜水蒸发极限埋深约为6 m。(4)随着地下水位埋深的增大,地表植被覆盖度逐渐降低,其植被蒸腾量也逐渐减小;而裸土的覆盖度则随地下水位埋深的增加而逐渐增大,裸土蒸发量也随之增大。(5)在地表蒸发量随地下水位埋深和NDVI变化的等值线图中,随着NDVI的增大,地表蒸发量的等值线向地下水位埋深增大的方向倾斜;在NDVI小于0.2的裸土区,潜水蒸发的极限埋深约为3 m;随着NDVI的增大,潜水蒸发的极限埋深也随之增加,最大可以达到6 m左右。对SEBS估算出的地表蒸发量在生态水文地质中的应用进行了探索:(1)银川平原的生态需水量等于年陆面蒸散量,即为38.16×108 m3。(2)建立了地下水位埋深的定量反演模型,对银川平原的地下水位埋深进行了遥感估算,其误差分布主要集中在地下水位埋深大于潜水蒸发极限埋深的地区,如贺兰山洪积倾斜平原、银川市的地下水位降落漏斗区等。(3)根据潜水蒸发极限埋深及潜水蒸发系数估算了银川平原2004年的潜水蒸发量为14.2×108 m3,并对植被覆盖条件下的阿维里扬诺夫潜水蒸发公式的参数化进行了探讨。更多还原

【Abstract】 Yinchuan Plain is in the north of Ningxia Hui Autonomous Region. As a rare oasis of artificial ecosystem, its stability depends on the quantity of regional water resource. In recent years, for the reason of the Yellow River zero flow, the volume of the Yellow River water available for Ningxia has decreased year by year. Irrational utilization of water resource aggravate the deterioration of ecological environment in the Yinchuan Plain, resulting in that major environmental factors lack of coordination, the function of natural ecosystem is weakened, the capacity of the environment is small, and the ecological balance is fragile. As a major component of regional water and energy balances, land surface evapotranspiration is extremely important not only in the processes of water and energy cycle, but also it is an important link between ecological and hydrological processes. Through the research of the temporal and spatial evolution of the land surface evapotranspiration and their impact factors in the Yinchuan Plain, we could understand the process of water cycle in the oasis thoroughly, and the results will provide decision support for rational development and utilization of water resource, allocation of land and water resources as well as protection of ecological environment.We estimated the land surface evapotranspiration of the Yinchuan Plain with MODIS remotely sensed data in the clear sky days and quantitative inversion model– SEBS (Surface Energy Balance System), calculated the evapotranspiration in the date of no available satellite remote sensing images, and the error was evaluated quantitatively, the results show that: (1) The land surface evapotranspiration of the Yinchuan Plain was about 38.16×108 m3 in 2004. (2) The evapotranspiration of the Yinchuan Plain measure up to maximum from early July to mid-August with about 3 mm/d. From mid-November to December and January, the evapotranspiration measure up to minimum, less than 0.5 mm/d.By means of spatial overlay and GIS multi-factor analysis of land surface evapotranspiration, land cover types, groundwater depth and NDVI, we arrive at a reasonable characteristic of the spatial distribution of evapotranspiration in the Yinchuan plain and its relationship with groundwater depth and vegetation cover, as well as the limit depth of phreatic water evaporation on different vegetation cover conditions, the results are as follows: (1) The land surface evapotranspiration has a significant difference between different land cover types in the Yinchuan Plain, and its descending order are: water, croplands, closed shrublands, grasslands, urban and built-up, open shrublands, barren or sparsely vegetated. (2) In the dry season, the spatial distribution of evapotranspiration in the Yinchuan Plain is mainly affected by groundwater depth. In areas of groundwater depth being less than 1.6 m, the evapotranspiration is very small as a result of the soil salinization. The evapotranspiration measures up to maximum when groundwater depth is 1.6 - 2.2 m, and then decreases with the increase of groundwater depth until being 4 m, so the limit depth of phreatic water evaporation of bare soil is about 4 m. (3) In the wet season, the spatial distribution of evapotranspiration in the Yinchuan Plain is mainly affected by vegetation cover and groundwater depth. The evapotranspiration decreases with the increase of groundwater depth until being 6 m, so the limit depth of phreatic water evaporation in the Yinchuan Plain covered by vegetation is about 6 m. (4) The land surface vegetation coverage decreases with the increase of groundwater depth, and the amount of vegetation transpiration is gradually reduced. But the evaporation of bare soil increases as a result of the coverage of bare soil increases with groundwater depth gradually. (5) In the contour map of evapotranspiration changes along with groundwater depth and NDVI, the contour of evapotranspiration decline to the deeper groundwater depth with the increase of NDVI. For the bare soil with NDVI less than 0.2, the limit depth of phreatic water evaporation is about 3 m. The limit depth of phreatic water evaporation increases with the increase of NDVI, and the largest of about 6 m can be achieved.We explored the application of the land surface evapotranspiration estimated by SEBS in eco-hydrogeology: (1) The ecological water requirement is equivalent to land surface evapotranspiration in the Yinchuan Plain, which is about 38.16×108 m3. (2) We established a quantitative inversion model for groundwater depth and estimated the groundwater depth in the Yinchuan Plain, and the error mainly distribute where the groundwater depth is deeper than the limit depth of phreatic water evaporation, such as Helan Mountain alluvial piedmont plain and the groundwater depression cone in the Yinchuan city. (3) The phreatic water evaporation of the Yinchuan Plain was about 14.2×108 m3 in 2004 which was estimated based on the limit depth of phreatic water evaporation as well as the phreatic water evaporation coefficient.更多还原