【作者】 马乐宽；

【导师】 倪晋仁；

【作者基本信息】 北京大学 ， 环境工程， 2008， 博士

【摘要】 快速识别流域内生态缺水严重的区域、动态评估生态用水状况对流域生态环境建设和水资源优化配置具有重要意义。本文借鉴水体快速生物评价方法的思想,建立了一种适于不同尺度的流域生态环境需水快速评估方法,并在黄土高原区的延河流域、纸坊沟流域开展了案例研究。流域生态环境需水快速评估方法包括以下主要步骤:(1)根据流域等级嵌套结构的特点,选择小流域为评价和计算单元;(2)基于流域内土地利用/覆盖和各种生态系统的内在关系,构建生态环境需水特征指标EWRI作为流域生态环境需水的表现因子;(3)针对不同的研究尺度,选择生态环境需水的影响因子作为环境因子;(4)以小流域为基本单元,进行表现因子与环境因子的数据集成;(5)以典型小流域单元作为参照单元,构建参照组;(6)以环境因子相似性作为判别依据,将待评估单元匹配到参照组中,计算其对各参照组的隶属度;(7)根据各参照组表现因子的平均特征及待评估单元对其隶属度,计算待评估单元表现因子的预测值;(8)进行评估单元表现因子预测值和实际值的对比,得到生态缺水度指标EWDI的值,以此为依据进行生态缺水严重程度的评估。以位于黄土高原区的黄河流域一级支流延河流域为研究区域,利用1990年与2000年两期土地利用/覆盖数据对流域生态缺水进行了评估。结果表明,安塞县南部、延安市周边及宝塔区是生态缺水最严重的区域。为此,进一步利用位于安塞县南部的延河二级支流纸坊沟流域1938～1999年15期的土地利用资料进行了生态缺水动态评估。结果表明,纸坊沟流域生态环境用水经历了“自然平衡-严重亏缺-逐渐改善-趋向平衡”的变化过程,这一过程与该流域的开发治理过程是一致的。案例研究的结果说明了流域生态环境需水快速评估方法的可行性、快速性。针对研究区以水土流失为首要生态环境问题的特点,以纸坊沟流域为例开展了基于水土保持的流域生态环境需水研究。结果表明:在允许土壤流失量1000 t/km~2·a的目标下,纸坊沟流域的生态环境需水量约为1.77×10~6m~3,占该流域降水资源总量的39.0%,这与1998年该流域的情景相当;适当降低水土保持目标可在一定程度上减少生态环境用水量。在纸坊沟流域生态环境需水研究结果的基础上进一步探讨了水土保持中“水保”和“土保”的关系。利用土壤侵蚀的特征指标和水流失的特征指标分别表征土壤侵蚀和水流失,分析了水流失与土壤侵蚀之间的关系,并对不同目标下的水土保持用水进行了讨论。结果表明:伴随着“土壤侵蚀”的“水流失”反映了生态环境水向潜在资源水和灾害水转化的趋势。1938～1999年间纸坊沟流域“水流失”与土壤侵蚀程度之间具有较好的相关关系。当流域出口测站的径流量约为6.77×10~4m~3时,不仅流域生态环境需水和社会经济用水能够基本得到满足,而且流域“土保”也可达到微度侵蚀的目标(侵蚀模数≤1000t/km~2·a)。更多还原

【Abstract】 Rapid identification of areas suffering serious Eco-environmental Water Deficit (EWD) and dynamic assessment of Eco-environmental Water Use (EWU) are of significance to ecological construction and sustainable utilization of water resources in a catchment. With the similar spirit as the prevailing rapid biological assessment methods for water body, a rapid assessment method in terms of Eco-environmental Water Requirement (EWR) was developed to address this point for different scales of catchments, and a case study was carried out on the Yanhe Basin and Zhifanggou Watershed located on the Loess Plateau.The method proposed herein contains 8 main steps, specifically, (1) partition of the study area into proper units; (2) construction of indicator of EWR (EWRI) for a basin; (3) selection of environmental variables; (4) integration of the data about EWRI and the environmental variables into the units obtained in step (1); (5) pick of typical units as the reference units and construction of reference groups, and the other units as test ones; (6) calculation of memberships of each test unit to all reference groups; (7) calculation of the expected EWRI of each test unit based on its degree of membership to and the average EWRI of each reference group; (8) with the observed and expected EWRIs of each test unit, an indicator of EWD (EWDI) could be calculated to show its severity of EWD.The method was applied to the Yanhe Basin with land use data of 1990 and 2000, and the result showed that the south of Ansai County, the Yan’an build-up surrounding areas and Baota District were suffering serious EWD. A further study was carried out on Zhifanggou Watershed located in south Aansai, a secondary tributary of Yanhe River, with land use data of 15 periods among 1938～1999. The result showed that the variation of its EWU experienced a process of“natural balance - severe EWD - gradual improvement - tending to balance”. This was highly consistent with the developed process in the watershed. These applications proved the proposed method of practicability and rapidness. The dominant objective of ecological construction in the study area is to prevent soil erosion. Therefore, this dissertation calculated the EWR of Zhifanggou according to certain objectives of soil conservation. The result showed that given a soil loss tolerance of 1000 t/km~2·a, the EWR of Zhifanggou was about 1.77×10~6m~3, 39.0% of the total annual precipitation, similar to the situation in 1998. Moderately reducing the objective of soil conservation can save a little EWR to some extent.In order to reveal the relationship between“water conservation”and“soil conservation”, analytical method of water resource structure was applied to discover the connotation of“water loss”. Furthermore, with Zhifanggou watershed as the study area, indicators for soil erosion and water loss were used to address the relationship between them, and the water use for soil conservation under deferent objectives was discussed. The result showed that as the concomitant of soil erosion, water loss reflected the transforming trends of water for entironment to that of latent resource and calamity. From 1938 to 1999, the degree of water loss and soil erosion in Zhifanggou had significant correlativity. The objective of soil conservation could be set to a soil loss tolerance of 1000 t/km~2·a, with a corresponding runoff of 6.77×10~4m~3 which could approximately meet the EWR of the river ecosystem and human water requirement.更多还原