【作者】 邵辉；

【导师】 高建恩；

【作者基本信息】 西北农林科技大学 ， 水土保持与荒漠化防治， 2013， 博士

【摘要】 由于人口增加、人类活动加剧,世界上很多河流出现降雨不减少、径流锐减甚至断流,严重影响流域及区域社会经济发展,使得人类活动特别是水土保持对河流的影响这一科学问题越来越受到关注。本研究选取具有典型意义的缺水高含沙重污染渭河作为研究对象,针对水土保持措施对河流影响研究的薄弱环节,开发了具有自主知识产权的水土保持梯田措施过程模拟模型并成功嵌入世界上广泛应用的SWAT模型当中,在对模型进行系统验证的基础上,研究了渭河区域水土流失与生态基流对梯田措施的响应,提出了基于水沙耦合及经济分析相结合的渭河流域水土保持梯田措施优化配置技术,初步构建了水土保持梯田措施模拟基本理论。取得的主要成果如下：(1)初步提出了“流域自响应理论”的概念,开发了具有自主知识产权的水土保持梯田措施过程模拟模型。提出了“流域自响应理论”的概念,认为流域系统内各部分是互相联系和运动的,运动的目标是追求系统的平衡。当系统平衡受到破坏,其系统将朝着建立新的平衡方向发展。在此基础上,设计了针对不同梯田类型的概化和分坡段模拟算法,并使用FORTRAN语言编译嵌入到SWAT流域水文模型中(第488版,累计新增代码1.8万行),实现了梯田措施对流域水土流失变化影响的模拟技术,补充了大型流域模型中水土保持措施对河流影响过程模拟的不足。(2)验证结果表明,新嵌入梯田模块的SWAT模型模拟精度较高,满足评价坡面及流域水土流失对梯田响应的技术要求。采用国内外梯田及黄土高原小流域水、沙、养分及作物产量实测资料对开发模型进行验证,结果表明：平衡偏差指标均小于0.1%,模型系统各部分功能均正常运行；反映坡面水土流失模拟值与实际符合程度的纳什系数(Nash-Sutcliffe Efficiency)在大多数条件下高于0.5,表明所开发模型能够反映坡面产流产沙及养分流失过程；梯田模块模拟的流域降水产流、产沙输沙过程偏差(PBIAS)介于-16.2%-11.2%,梯田调控效应模拟与实测结果基本吻合。表明水土保持梯田措施数学模型开发较为成功,模拟精度较好,可用于坡面及流域水、沙及养分流失过程的模拟。(3)利用基于“流域自响应理论”的新嵌入梯田模块SWAT模型对渭河径流泥沙进行初步模拟,结果表明现有水利水保措施对减少渭河河床淤积意义重大。利用上世纪60年代渭河来水来沙变化较为剧烈的资料,对模型进行参数提取和验证,结果表明模型计算纳什系数(NS)以及相对偏差(PBIAS)分别介于0.52-0.93和-16.21%-28.35%之间,该模型可较好的模拟渭河中上游地区水沙剧烈变化过程。基于1960-2009共计50年气象资料模拟结果表明,渭河干流中上游集中了渭河枯水期径流量的89.4%,对生态基流保障意义重大；而且反映出汛期来沙量占全年输沙量的86.4%,水土流失主要发生在汛期；如果不对渭河流域进行治理,渭河上中下游干流区域河床年均抬升将达到4cm、10cm和20cm,约为实测多年平均值的1.5倍,河床淤积剧烈,说明现有水土保持等措施对减少渭河河床淤积意义重大。(4)利用所建立模型,在系统研究渭河流域水土保持梯田措施对流域水沙影响的基础上,重点研究了梯田措施对河流生态基流的影响。结果表明梯田措施蓄洪补枯、削减侵蚀、防止淤积、增加生态基流。2000年规模梯田(约占干流面积10%)可减少流域年均总产流量约0.37亿m3,减少咸阳站年均输沙量1620万t,但增加咸阳站最枯月径流量3.5%,减少近期和远期生态基流不满足天数3.1和5.5天,分别占不满足总天数的26.3%和27.2%。自上世纪70年代至2009年,梯田修建已累计减少渭河上游和中游干流区域泥沙淤积1.01亿t和0.66亿t,防止河床抬升9.1cm和22.8cm,对于渭河上中游干流治理、洪水防治以及河流水质的改善具有重要的现实意义。(5)基于新嵌入梯田模块的SWAT模型及水沙耦合经济分析的流域优化配置技术可为水土保持梯田措施优化、规划配置及智能决策提供技术支撑。基于对四种典型优化配置模式进行初步分析结果表明,水平梯田减沙及减少河流泥沙浓度的能力大于隔坡梯田,但隔坡梯田投入产出比显著高于水平梯田。建议在黄土高原生态环境建设过程中首先判定侵蚀关键区域,对水土保持措施进行前期优化及合理布局,同时适量建设隔坡梯田,以达到更好的治理效果和投入产出比例。更多还原

【Abstract】 In recent years, runoff in many rivers of the world has been declined rapidly and even broken off due to population growth and the accelerated human activity influence. This problem has seriously affected regional social and economic development, which focuses people’s sight on the scientific question about the influence of human activity such as soil and water conservation measures toward rivers. Therefore, this research took the Weihe River as research object, which is a typical river with characteristics such as gross pollution, water shortage and high sediment concentration. Based on the research weakness of the soil and water conservation effects on rivers, this study developed a process-based terrace algorithm with independent intellectual property rights and incorporated it into the widely used Soil and Water Assessment Tool (SWAT) model. The response of soil and water loss and ecological base flow toward terraces of the Weihe River basin were detected using the newly developed model after its systematic verification. And an optimization technology was given based on the terrace model and the combined water and sediment analytical method and the economy analytical method. The above achievements preliminarily formed the basic theory for terrace simulation. The main conclusions were as follows:(1) A process-based terrace algorithm within the SWAT model was developed based on the preliminary "Watershed Self-response Theory" proposed in this research. This research proposed the concept of "Watershed Self-response Theory", which indicated that all parts of the watershed were connected and moving with the purpose of a balance statuse. The system will moving toward a new balance if the old one was interrupted. Based on this theory, a terrace simulation theory and method was developed with physical and mathematical models as the basic tools after analyzing the requirements of modelling terrace effects on river. The goal of the simulation theory was to reveal the water and nutrient cycle in the watershed level. Description method for different types of terraces and the segment simulation method were designed and incorporated into the SWAT model (version488with about18,000lines of newly added codes) using FORTRAN. The accomplishment of the terrace simulation technology fulfilled the tool needs of simulating the terrace effects toward soil and water losses in the watershed scale, which also improved the process-based effects simulation techology of soil and water conservation measures towards rivers.(2) The verification result indicted the satisfactory accuracy of the newly developed model and the feasibility of using the model for evaluating the soil and water loss response to terrace in both field and watershed scale. Observed runoff, sediment, nutrients and crop yield data of terraces in China and the U.S.A, and runoff and erosion data in typical small watershed in the Loess Plateau were employed for testing the newly developed model. The average balance testing indicators were less than0.1%which indicated that all functionalities of the model worked well. The field scale soil and water loss simulation Nash-Sutcliff Efficiency was usually higher than0.5which demonstrated that the model could reveal the runoff, sediment and nutrients loss processes in the field scale. The predicted runoff and erosion percent bias (PBIAS) in watershed level were between-16.2%and11.2%, and the modeled terrace regulation rate were similar to the measured data. Verification result proved the successful development of the new SWAT model and its accuracy in simulating runoff, sediment and nutrients yields from terrace in both field and watershed scale.(3) The newly developed SWAT model based on the "Watershed Self-response Theory" was used to simulated the runoff and sediment in the Weihe River and indicated the important effects of water conservation and conservancy measures on stopping river bed rising. The SWAT model was calibrated and validated using the highly varied runoff and sediment data collected in the1960s. The model could give satisfactory prediction for the main Weihe River runoff and sediment with NS and PBIAS ranging between0.52-0.93and-16.21%-28.35%. Based on the50years simulation result from1960to2009, the upstream and middle stream runoff in the drought season accounted for about89.4%of the whole river which was important for guaranteeing the ecological flow. The erosion mainly happened in the flood season which accounted for about86.4%of the annual sediment. The model also indicated that the up, middle and down-stream of the main river bed would have a4cm,10cm and20cm annual rise and lead to serious river deposition without human regulation, which was about1.5times of the observed value. This result indicated that the completed water conservation and other measures had great impact on stopping river bed rising.(4) Terrace in the main Weihe River basin could delay the flood and add the drought season runoff, prevent erosion and decrease river deposition, which were helpful for preventing soil and water loss and guaranteeing ecological base flow. Terrace in2000(about10%of the total basin area) could decrease about37million m3annual water yield in the whole watershed, and reduce16million tons of annual sediment transported in the Xianyang station. The most dry month runoff increased by3.5%and the short-term and long-term substandard days for ecological flow decreased by3.1and5.5days (accounted for26.3%and27.2%of the total substandard days) due to terrace practices. During1970s and2009, the construction of terraces had decreased upstream and middle stream sediment deposition by101and66million tons, which equals to9.1cm and22.8cm river bed lifting respectively. These effects were important for the main river controlling, flood preventing and water quality improving.(5) Optimization technology was achieved based on the terrace model and the combined water and sediment analytical method and the economy analytical method, which provided technical support for terrace distribution and structure optimizing, watershed planning and the smart decision. Based on the analysis result of4typical terrace optimization scenarios, the runoff and sediment reduction capacity of the bench terrace were higher than normal terrace, while the input-output ratio of the normal terrace was significant higher due to its cheaper price. It was recommended that erosion critical area should be firstly located for soil and water conservation measures optimization and reasonable distribution. Normal terrace should also be a consideration in the Loess Plateau eco-environmental construction for better erosion controlling effect and input-output ratio.更多还原