Knowledge Resource Center for Ecological Environment in Arid Area
| 气候变化和人类活动驱动的贺兰山西麓流域水环境变化 | |
| 其他题名 | Water Regime Changes by Climate Change and Anthropogenic Activities in an Inland Watershed of Western Helan Mountain |
| 李锦秀 | |
| 出版年 | 2009 |
| 学位类型 | 博士 |
| 导师 | 肖洪浪 |
| 学位授予单位 | 中国科学院寒区旱区环境与工程研究所 |
| 中文摘要 | 贺兰山一线是我国一条重要的地理分界线。贺兰山西麓流域既是荒漠化危机区，又是农牧交错区，是全球变化的一个敏感区。上世纪70年代以后，各种人类活动如过度放牧、农林垦殖、森林砍伐、城市（镇）化等不断增强，对该区域的水循环过程产生了深刻影响，导致区内水资源空间格局发生重大变化，由此也引发了许多生态环境问题。该地区出现的水环境问题，具有西北地区内陆盆地的典型性。本研究旨在探讨贺兰山西麓流域水循环的特点，及其对气候变化和人类活动的响应模式，科学评价流域水资源，为区域社会经济发展和生态建设战略提供水资源可持续利用方面的科学依据。\n论文以水循环理论为指导，首先从全流域尺度了解气候演化和人类活动的历史，认识流域水环境变化的宏观规律；接着在灌区尺度上，对农田土壤-植物水分循环进行试验观测和模型模拟，评估了灌溉水利用效率，提出灌区水资源优化利用建议；继而在盆地尺度上，分析查哈尔盆地地下水循环过程，重点研究受人类活动强烈影响的井灌区现代地下水补给、径流与排泄等变化过程，对灌区地下水资源总均衡进行了估算；最后，在区域尺度上讨论了贺兰山西麓山前平原区快速城市化进程的水文水资源效应。研究主要结论如下：\n1．对流域气候演化和人类活动的历史研究表明：（1）贺兰山西麓地区的荒漠景观是在整个第四纪以来的干旱气候影响下形成的，具体表现为山区植物物种的生长和分布逐渐受到限制；山前洪积扇逐渐退缩，西部腾格里和吉兰太地区湖泊消失，形成沙漠。（2）在千年尺度上，贺兰山山峰积雪由终年积雪转为冬春积雪，积雪下线逐渐升高，反映出气候逐渐变暖的趋势；在两百年尺度上，贺兰山地区存在明显的暖干化趋势，气温与降水的变化始终存在数年或数十年尺度的波动；而在近半个世纪，研究区降水表现出一定程度的下降趋势，温度则表现出上升趋势。（3）人类对贺兰山水源涵养林的破坏主要是在秦汉和西夏时期，大约在明末清初，原始林消失，代之而起的为天然次生林。(4) 20世纪70年代以来，流域内大规模拦蓄引用地表水和开采地下水，再加上超载过牧、人工绿洲系统的扩张，结果使水资源系统的时空分布发生根本改变，引起了一系列水环境变化。总之，气候变化和人类活动共同影响着贺兰山西麓流域的水循环状况，而近50年来流域水环境状况不断恶化，主要是流域水土资源开发与流域水循环系统演变规律及特性不相适应的矛盾所决定的。\n2．对灌区田间尺度水肥利用效率与氮肥面源污染评价发现：（1）优化方案比传统方案节水25%，但两种方案在整个玉米生育期，土壤各层含水量变化没有明显区别，玉米产量差异不显著，说明过多的灌水其实并不能被充分的利用。（2）在大定额灌溉的影响下，玉米大部分根系集中在0～60cm深度范围以内。（3）施氮量可以显著影响土壤中硝态氮的累积和分布，但对铵态氮的影响较小。过量施氮导致硝态氮在土壤中累积，提高硝态氮随水分淋溶危险。（4）用RZWQM模型对玉米生长和土壤水分运移进行模拟，结果令人满意，为进一步应用该模型评价不同水肥管理措施下的水氮利用效率奠定基础。\n3．贺兰山西麓第四纪断陷盆地内的地下水主要为地质历史时期补给的“古水”。查哈尔盆地的地下水氢氧同位素组成与其北部地区的地下水氢氧同位素组成明显不同，表明不同地区地下水在补给来源和循环历程上存在差异。地下水CFCs测年结果则发现，查哈尔滩灌区地下水中混有“现代水”补给的迹象。\n4．经多年大规模开采，查哈尔滩灌区地下水化学发生了极大变异。本次采样全灌区不同位置地下水矿化度变异系数52%，NO3-含量变异系数高达136%，有41%样品地下水中NO3-含量大于世界卫生组织规定的饮用水标准。与灌区开发前相比，全灌区地下水NO3-含量普遍增加。在空间分布上，灌区内NO3-的高值分布区恰好与灌区内部的一些高矿化度地下水分布区完全吻合，并且主要集中在绿洲内开发较早、人类活动强烈的地区。\n5．查哈尔滩灌区地下水资源总均衡估算发现，灌区地下水资源呈负均衡状态。每年灌区开采量高达1527.04×104m3/a，补给量却只有1042.39×104m3/a；地下水利用每年消耗储存量268.44×104m3/a，导致地下水位下降0.4m/a；灌区年开采量的15%左右又补给地下水，不仅浪费提水消耗电能，而且造成地下水污染。\n6．随着人口增加和城市规模不断扩大，处于贺兰山山前平原的巴彦浩特城市供需水矛盾日益严峻，现状年缺水量138.2×104m3，到2020年，年缺水量将高达1511.2×104m3。与此同时，城市化快速发展的驱动下，大量开发利用地下潜流和深层地下水，结果使地下水位降低，泉水溢出量减少；城区不透水面积增加，改变了洪峰频率分布和洪水路径；城市污水排放，导致地下水水质恶化。 |
| 英文摘要 | Helan Mountain is an important geological boundary in China. Western watershed of the Helan Mountain belongs to inland river basin of China and suffered from both desertification threat and intensive anthropogenic pressure. This area is also important to global change studies because of its location on the northern margin of the East Asian summer monsoons. Since 1970s, anthropogenic activities such as over-grazing, agricultural development, forest cut and urbanization has intensified in the area. These activities has changed water cycle in the watershed and resulted in significant evolution of spatial water resources distribution. Consequently a series of ecological environment issues has occurred. The water regime changes in the area are typical in inland river basins of northwest China. This study aims to find water cycle characteristics in the watershed and identify their impacts by climate change and anthropogenic activities. Results of this study will provide scientific support for evaluation of water resources in the area and help to formulate regional socioeconomic development plan and ecological restoration strategy based on sustainable water resources management.\nGuided by water cycle theory, this dissertation first analyzes history of climate change and human activities in the area in order to understand water regime changes in the whole watershed. Then both field experiment and model simulation are carried out to understand water movement in soil-plant system and to evaluate irrigation water use efficiency. And then groundwater evolution in a Quaternary basin, Chahaer Basin, is studied and the change of groundwater flow, recharge and discharge over the past 50 years is highlighted in an irrigated oasis. Water balance at oasis scale is calculated. At last, urbanization impacts on water regime and water resources distribution are discussed at a regional level. Main conclusions from our study are listed as following.\n1. Through study of history of climate change and human activities in the watershed, we find: (1) Desert landscape in the area has formed since Quaternary period when climate became drying, including: distribution of plant species in Helan Mountain was confined of specific altitude; alluvial basin in front of the Mountain moved back and shrunk gradually; lakes in Tengeli and Jilantai areas were dried and disappeared. (2) In millennium scale, appearance of snow cover in Helan Mountain had changed from all year around to only in winter and frozen line gradually moved toward higher mountain, reflecting trend of climate warming in the time. In 200a scale, climate in Helan Mountain also shows the trend of warming and drying with which precipitation and rainfall had fluctuated between higher and lower values in several years or decadal years intervals. Climate records over the past half century show precipitation in the area decreases in certain extent but the temperate increases implicitly. (3) Anthropogenic activities which had great damage to the water-holding forest in the mountain were mainly occurred in Qin, Han and Xixia dynasties. Consequently aboriginal forests were disappeared and secondary forests started appear in late Ming or early Qing dynasty. (4) Large-scale surface water withdrawal and groundwater abstraction has occurred since 1970s. Meanwhile remarkable land use change has happened in the watershed due to over-grazing and man-made oasis expansion, which has changed temporal and spatial water resources distribution and resulted in many eco-hydrological problems. In general, water regime in the western watershed of Helan Mountain has been affected by both climate change and anthropogenic activities. The deterioration environment of water cycle in the watershed over the past 50 years has mainly caused by the conflicts between unreasonable soil and water development and fragile water cycle system. \n2. Results from the observation of soil water movement and nitrogen concentration in maize field show, (1) The optimum treatment saves 25% of water than the traditional treatment but soil water moisture in same layer behaved similarly in the whole maize growth period, meaning the over-irrigated water could not be used by plant effectively and there is no significant difference between the yields of two treatments. (2) Root distribution shows most of roots are located in 0～60cm soil depth. (3) Fertilizer application could influence nitrate nitrogen in soil profile but has little effect on ammonium nitrogen. Over-application of agricultural fertilizer results in nitrate accumulated in soil profile and increase potential treat of nitrate leaching with excessive irrigation water. (4) Soil water modular and plant growth modular of RZWQM is calibrated with the Chahaertan field data and the simulation results are reasonable satisfied. This work provides valuable experience for further using the model to predict best practices for maize growth in the area.\n3. Groundwater in Quaternary basin is mainly recharged in ancient time. The stable isotope in Chahaer Basin is quite different with that in its northern area, meaning the difference of groundwater recharge source and water cycle process in those different areas. Using CFCs as residence time indicator, it finds groundwater within the aquifer of Chahaertan oasis mixes between older (>50 years) and recent components although the proportion of older water is much higher than recent recharge. \n4. Significant evolution has occurred in terms of groundwater chemicals in Chahaertan oasis since it was developed. The study of groundwater chemicals in 2006 shows great spatial variance, of which the conductivity variability is 52% and nitrate concentration variability is as high as 136%. Total of 41% of groundwater samples has remarkably high nitrate concentration that exceeds the World Health Organization drinking water standard. Groundwater with elevated nitrate concentration also has high conductivity and the locations are in the oasis where human activities have happened in early stage and more intensive. Comparing with the groundwater before the oasis developed, nitrate concentration has increased significantly in the whole oasis.\n5. Water balance at oasis scale is calculated and negative balance of groundwater resources in Chahaertan oasis is detected. Groundwater abstraction is as high as 1527.04×104m3/a but recharge is only 1042.39×104m3/a; around 268.44×104m3/a groundwater reserve is abstracted each year, caused falling of water table 0.4m/a; every year, approximately 15% of water abstraction flows back to groundwater table as return flow. Thus not only wastes electricity consumption for pumping water but also causes potential treat of groundwater pollution. \n6. With population growth and urbanization, Bayanhot City, which is situated in the fragile tableland in front of Helan Mountain, is facing serious conflicts between water supply and demand. The water shortage at current stage is 138.2×104m3/a; it will reach to 1511.2×104m3 in 2020. Meanwhile, driving by the rapid urbanization, large-scale abstraction of shallow and deep groundwater has resulted in falling of groundwater table and reduction of spring flow; increase area of non-permeable surface has changed flood distribution and frequency; discharge of urban wastewater has potential threat to groundwater quality. |
| 中文关键词 | 贺兰山西麓流域 ; 水环境 ; 气候变化 ; 人类活动 ; 地下水演变 ; 城市化 |
| 英文关键词 | Western watershed of Helan Mountain Water regime Climate Change Anthropogenic activities Groundwater |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286728 |
| 推荐引用方式 GB/T 7714 | 李锦秀. 气候变化和人类活动驱动的贺兰山西麓流域水环境变化[D]. 中国科学院寒区旱区环境与工程研究所,2009. |
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