【作者】 张文化；

【导师】 魏晓妹；

【作者基本信息】 西北农林科技大学 ， 水文学及水资源， 2009， 硕士

【摘要】 石羊河流域是我国典型的干旱内陆区,地下水资源作为该区水资源的重要组成部分,不仅是绿洲经济发展的重要水源,而且也是生态环境的重要支撑。而近几十年来,气候的变化和绿洲农业发展对水资源的开发利用,加剧了外部环境对地下水系统的影响,产生了地下水位大幅度下降、植被退化、土地沙化及土壤盐渍化问题,严重影响着流域地下水资源的持续利用和生态环境安全。因此,研究气候变化和人类活动对地下水动态的影响,探讨地下水动态变化的生态环境效应,对石羊河流域地下水资源的可持续利用和生态环境保护具有重要的理论意义和应用价值。本文从石羊河流域地下水循环的角度出发,分析了变化环境对流域平原区地下水动态的影响,建立了地下水位埋深动态模拟模型,基于地下水动态变化的生态环境效应的分析,进行了地下水位动态调控模拟研究。论文的主要研究结果如下:(1)从地下水系统的角度,分析了石羊河流域地下水动态的时空变化特征。分析结果表明:1984～2001年流域平原区地下水位呈显著下降趋势,其中武威盆地地下水位平均下降6～7m,下降速度0.31m/a;民勤盆地地下水位平均下降10～12m,下降速度0.57m/a。1997～2003年地下水的硬度和碱度值呈波动趋势,变化幅度不大;而PH值和矿化度整体上呈上升趋势,变化明显。(2)基于地下水动态的影响因素分析,运用气候倾向率法和Kendall秩次相关法对石羊河流域平原区1960～2005年的气温、降水量和蒸发量进行趋势分析,结果表明:气温变化趋势同全球气候变暖的趋势一致;降水量稍有增加,但绝对幅度变化不大;蒸发量呈波动小幅下降趋势。而近20多年来,灌溉面积扩大、渠系衬砌及开采地下水等人为因素加强了对地下水循环的影响,使地下水补给量减少,排泄量增加,导致平原区地下水位大幅度下降。(3)运用SPSS软件的主成分回归法对流域平原区地下水动态变化的主要驱动因素进行了研究。研究结果表明:武威盆地人为因子对地下水位埋深的影响占总影响力的62.82%,气候因子占总影响力的37.18%。由此可见,武威盆地地下水位动态变化的主要驱动因素为灌溉面积、地下水开采及渠系衬砌率。民勤盆地人为因子对地下水位埋深的影响占总影响力的79.12%,气候因子占总影响力的20.88%。因此,民勤盆地地下水位动态变化的主要驱动因素为红崖山入库径流量与地下水开采量。(4)运用Elman动态神经网络模型和基于小样本数据的支持向量机模型分别模拟了武威盆地和民勤盆地1991～2000年的地下水位埋深,并对2001～2002年的地下水位埋深做了预测,经过检验两个模型的模拟误差都比较小,Elman模型在±0.4%以内,支持向量机模型在±0.2%以内;而预测误差略大,Elman模型在±7%以内,支持向量机模型在±5%以内。通过模型比较得出支持向量机模型的归一化均方根误差都小于Elman模型的归一化均方根误差,支持向量机模型的模拟预测效果略优于Elman模型。但从总体上来看,两类模型都可以定量模拟气候因素、人类活动、地表来水量变化对地下水位的影响。(5)通过分析地下水位动态变化对水环境、植被环境、土壤环境的影响,在参考同类区域已有研究成果的基础上,认为石羊河流域平原区的生态地下水位埋深为3.0～4.0m。为了防止流域下游生态环境的进一步恶化,通过支持向量机模型模拟预测了两种不同情景下的民勤盆地地下水位埋深的恢复情况。更多还原

【Abstract】 Shiyang River Basin is the typical inland arid region in the west area of China.The groundwater is an extremely important part in water circulation of this area. It is not only important sources of economic development but also an important support for ecological environment.In recent years, with the development of oasis agriculture, intensified the influence by external environment into groundwater system. These caused the function of groundwater system slump disastrously,maked the groundwater table drop large scale, the vegetation degenerate, the land desertification and the soil salinification. These all have a serious influence for the groundwater sustainable use and ecological environment security. So,the study of climate change and human activities on the impact of groundwater resources and the sustainable use of ecological and environmental protection is an important theoretical significance and application value in the Shiyang River Basin.This article embarking from the water resources transformtion of the inland region in Shiyang River Basin, analysising the influence that the variational environment to groundwater dynamic, establishing dynamic simulation model of groundwater level,revealing the effect groundwater dynamic change to ecological environment, carrying on dynamic simulation of water table control. The main results are as follows:(1) From the perspective of groundwater system, analysising the temporal and spatial variation of groundwater characteristics in the Shiyang River Basin. The results show that the groundwater level showed a significant trends to drop, in which the groundwater level dropped by an average of 6~7m in Wuwei basin.The rate of decline is 0.31m/a. The groundwater level dropped by an average of 10~12m in Minqin basin.The rate of decline is 0.57m/a. The hardness and alkalinity of groundwater fluctuations in the value of positive trends, changed in marginally. The PH value and the overall degree of mineralization change significantly.(2) Based on the groundwater dynamic factor, analyzing the trend of 1956~2000 temperatures, the rainfall and the evaporation in the Shiyang River Basin, obtained the temperature change tendency to be consistent with the global climate warming. The precipitation has slightly increase, but the absolute amplitude variation is not big. The evaporation has slightly drop. In the recent 20 years, the human activity (expanding irrigated area, eliciting surface water irrigation, exploiting groundwater) strengthened the influence to the groundwater cycle,reduced the groundwater supplies,increased the excretion. Climatic change combine human activites caused the plain groundwater level drop a large scale.(3) Using the principal component regression analysis to analyze the effect and get the contribution rate of climatic change and human activites on groundwater in Wuwei Basin and Minqin Basin. The results show human factor’s effect accounts for 62.82% of the total effect and climate factor’s effect accounts for 37.18% in Wuwei Basin.This shows the main driving factor for dynamic changes in groundwater level is the irrigated area, groundwater exploitation and canal lining rate in Wuwei Basin.Human factor’s effect accounts for 79.12% of the total effect and climate factor’s effect accounts for 20.88% and in Minqin Basin. The main driving factor for dynamic changes in groundwater level is the main drivers of change for the Hongyashan Reservoir storage and groundwater runoff production in Minqin Basin.(4)Using the Elman dynamic neural network model and SVM analog modeling based on the small sample separately simulate groundwater depth of the Wuwei basin and Minqin basin in 1991~2000, and forecast groundwater depth to 2001~2002. The simulated errors quite to be small of two models after examination,Elman model in less than±0.4%, SVM model in less than±0.2%.But the prediction error is big, Elman model in less than±5%, SVM model in less than±7%. Obtained the normalized root mean square error of the model of support vector machine are smaller than the Elman model normalized root mean square error. The SVM simulation forecast effect is slightly better than the Elman. Generally speaking, two types of model can be quantitatively simulated the impact of ground water level to climatic factors, human activities, changes in surface water.(5) The ecology groundwater depth is 3.0~4.0m in Shiyang River basin plain through analyzing the influence that groundwater dynamic change to water environment, vegetation environment, soil environment.The present groundwater depth of downstream Minqin area has not been able to maintain the good ecological environment by far. In order to prevent the downstream ecological environment further worsening, this article forecast Minchin basin groundwater depth under two kind of different scene situations through the SVM model. The forecasting result indicated, in other condition invariable situation, increased the runoff of Hongyashan Reservoir has a more vital role than reduced exploiting groundwater volume to restore the groundwater depth.更多还原