基于Nash瞬时单位线法的渗透坡面汇流模拟

基于Nash瞬时单位线法,结合Horton土壤入渗经验模型,并考虑植被对降雨的截流作用,建立了渗透坡面汇流计算的数学模型。以矩形坡面为研究对象,基于其汇流时间-面积特性,推导建立了Nash瞬时单位线参数n、K的确定方法。其中参数n的值与坡面汇流时间-面积曲线指数相等,K的值与坡面汇流时间相等。应用本文建立的模型,对林地渗透坡面降雨径流进行计算,并与实测值进行比较。结果表明,计算值与实测值的变化趋势基本吻合,初步验证了本文方法的合理性。     

异参离散广义Nash汇流模型及应用

在广义Nash汇流理论基础上发展而来的离散广义Nash汇流模型,概念明确,结构简单,便于应用,但模型中各线性水库的调蓄参数K是相同的,致使其在河道地形(坡降和断面形状)变化较大河段应用时有其局限性。通过引入异参瞬时单位线及其S曲线,在离散广义Nash汇流模型概念解析的基础上,推导得出了异参离散广义Nash汇流模型,从而丰富了现有广义Nash汇流理论,扩大了离散广义Nash汇流模型的适用范围。实例分析表明,由于考虑了参数K的空间异质性,异参离散广义Nash汇流模型可以进一步提高河道洪水的模拟精度。     

论流域汇流的数学模型(第一部分 线性模型)

本文分线性与非线性两部分论述流域汇流的数学模型.在这第一部分线性模型中,主要提出并回答了线性汇流一般性微分方程式的初值问题;论述了瞬时单位线的分类;提出了可以消除负脉冲的马斯京贡(Muskingum)型模型的积分解;给出了纳希(Nash)瞬时单位线的(包括n为整数与非整数)和马斯京贡型三参数瞬时单位线的时段汇流曲线转换公式等.对纳希瞬时单位线的若干特性作了分析和讨论.     

考虑降雨空间分布的地貌瞬时单位线汇流模型探究与应用

降雨空间分布的不均匀性对洪水预报精度有着重要的影响,提出基于数字高程模型和降雨空间分布规律的地貌瞬时单位线汇流计算方法,进一步补充地貌瞬时单位线汇流理论。选取横山水库流域作为研究对象,利用DEM数据提取流域地形地貌特征,结合历史洪水期间的降雨空间分布律计算得到地貌瞬时单位线。选取2013年~2015年期间3场典型洪水进行模拟验证,结果表明考虑降雨空间分布的地貌瞬时单位线洪水模拟效果良好,优于传统地貌瞬时单位线。     

城市屋顶降雨径流过程单位线模型研究

城市屋顶按透水性质可分为不透水与绿色(渗透)屋顶。对于绿色屋顶,基于土壤水饱和下渗理论,考虑基质土壤层厚度有限性及表面积水深影响,推导建立了降雨径流过程的单位线模型,再联合不透水屋顶降雨径流过程单位线模型,共同构成城市屋顶降雨径流过程的单位线模型,并建立了统一的数学方程表达形式,参数包括响应速率与径流(产流)起始时间。其中,对于不透水与绿色屋顶,模型响应速率参数分别为坡面汇流时间的倒数与基质土壤层稳渗时间的倒数。根据不透水与绿色屋顶降雨径流过程实际监测数据,分别采用单位线模型进行了模拟,取得了良好的模拟效果。模型参数比较分析表明,绿色屋顶降雨径流削减效应主要依赖于基质土壤层的雨水蓄存作用,增大基质土壤层厚度可以增大雨水渗蓄量,并有效削减径流前期峰值,但对后期峰值的削减效应有所减弱,并会延长表面积水的排水时间。     

变动单位线及综合变动单位线的探讨

一、引言 天然流域的雨洪汇流过程,一般是非线性的。影响汇流非线性的原因十分复杂,包括降雨特性、河道底水以及水源组成比例等等。雨强是引起非线性现象的重要因子,雨强不同,单位线峰值和形状都不相同,国内外都有过论述及试验和实测资料的验证。目前在洪水预报和洪水计算中广泛使用的单位线(Sherman单位线和Nash瞬时单位线)都是线性单位线,一般是通过建立雨强和单位线要素(或参数)的经验关系来作非线性     

尼尔基水库控制流域伽玛分布地貌瞬时单位线推导

本文采用线性特征河长的概念,结合流域地貌特征,根据概念性流域地貌汇流模型的一般理论,以概念性元素"特征河长河段"模拟各级河道的汇流作用,建立了基于线性特征河长河段的伽玛分布地貌瞬时单位线模型。推导出了尼尔基水库控制的四级流域瞬时单位线的表达式,讨论了参数的约束条件和参数的推求方法,并分析了模型参数对瞬时单位线的影响。     

数字滤波法分割基流的论证

基流是河川的重要组成部分,基流划分的正确性直接影响对流域的水文分析,如流域的降雨径流关系、坡面汇流等。应用修改后的适用于场次洪水的数字滤波法及斜线分割法对总径流进行分割,并用分割后的地面径流与降雨资料建立降雨-径流相关图,推求流域的瞬时单位线,拟合洪水。结果表明,数字滤波法分割的基流比斜割法更平滑,更符合流量过程线退水段的物理规律,且其获得的瞬时单位线的确定性系数较斜割法高。     

Nash瞬时单位线法推求老凤河设计洪水

设计洪水是水文规划和水利工程建设规模论证的一项重要研究工作,文章介绍了Nash瞬时单位线法的基本原理与计算步骤,该法概念清楚,物理参数意义明确且容易推求,广泛应用于无实测资料的河道汇流及设计洪水过程线及设计洪峰流量的计算。以北京市大兴区某输变电工程电缆隧道穿越老凤河工程为例,采用Nash瞬时单位线法计算了穿河断面处设计洪水过程线及设计洪峰流量,并与已有研究成果进行对比,对比结果显示该法适用于老凤河设计洪水计算,为下一步分析河道洪水对穿河工程的防洪安全影响提供依据。     

TOPMODEL模型在半湿润地区径流模拟分析中的应用及改进

为了使TOPMODEL模型结构更合理,并能够用于半湿润地区或半干旱地区的径流过程模拟,文章对TOPMODEL模型的蒸发产流模块以及汇流模块进行改进,在蒸发产流模块中添加植被冠层截留蒸散发模型和Holtan超渗产流模型,汇流模块中坡面汇流采用瞬时单位线模型,河道汇流采用马斯京根河道洪水演进模型。通过对半湿润地区流域内降雨径流过程的模拟验证,表明通过对TOPMODEL模型的改进,模型对半湿润地区的降雨径流过程模拟精度有很大的提高,拓展了TOPMODEL模型适用范围。     

李子溪流域水土流失及泥沙输移规律初步研究

为了探讨长江上游流域水土流失及泥沙输移规律，选取嘉陵江中游的支流李子溪为典型流域进行分析研究，在实地调查，野外测验及应用１９６０年－１９９１年实测降雨、径流、输沙资料的基础上，利用单因子相关分析和多因子回归分析，分别建立了输水利沙量、最大输沙率计算方程。在此基础上，参照径流瞬时单位线原理，以线性时不变系统为基础，建立输沙瞬时单位线模型。通过输沙单位线与时段净侵蚀量的卷积得到流域出口断面的输沙率过程     

Estimation of the Velocity Parameter of the Geomorphologic Instantaneous Unit Hydrograph

The problem of estimation of the velocity parameter in the exponential distribution geomorphological instantaneous unit hydrograph (ED-GIUH) is investigated in this study. The main difficulty in applying the ED-GIUH model is the estimation of this parameter. In the present study, the ED-GIUH model is applied to six watersheds in Indiana, U.S.A. The relationships between the velocity parameter and climatic as well as basin geomorphologic parameters are investigated. The results of the study indicate that the velocity parameter is related to effective rainfall depth, total basin area and cumulative slope; it does not depend on runoff characteristics. Therefore, the ED-GIUH model can be used for estimating discharge hydrographs from ungauged watersheds.     

Evaluation of three unit hydrograph models to predict the surface runoff from a Canadian watershed

The predictability of unit hydrograph (UH) models that are based on the concepts of land morphology and isochrones to generate direct runoff hydrograph (DRH) were evaluated in this paper. The intention of this study was to evaluate the models for accurate runoff prediction from ungauged watershed using the ArcGIS^® tool. Three models such as exponential distributed geomorphologic instantaneous unit hydrograph (ED-GIUH) model, GIUH based Clark model, and spatially distributed unit hydrograph (SDUH) model, were used to generate the DRHs for the St. Esprit watershed, Quebec, Canada. Predictability of these models was evaluated by comparing the generated DRHs versus the observed DRH at the watershed outlet. The model input data, including natural drainage network and Horton's morphological parameters (e.g. isochrone and instantaneous unit hydrograph), were prepared using a watershed morphological estimation tool (WMET) on ArcGIS^® platform. The isochrone feature class was generated in ArcGIS^® using the time of concentration concepts for overland and channel flow and the instantaneous unit hydrograph was generated using the Clark's reservoir routing and S-hydrograph methods. An accounting procedure was used to estimate UH and DRHs from rainfall events of the watershed. The variable slope method and phi-index method were used for base flow separation and rainfall excess estimation, respectively. It was revealed that the ED-GIUH models performed better for prediction of DRHs for short duration (≤6 h) storm events more accurately (prediction error as low as 4.6–22.8%) for the study watershed, than the GIUH and SDUH models. Thus, facilitated by using ArcGIS^®, the ED-GIUH model could be used as a potential tool to predict DRHs for ungauged watersheds that have similar geomorphology as that of the St. Esprit watershed.     

对模糊识别单位线法中权重问题的探讨

单位线选择中考虑的因素很多:如雨强、降雨量、流域前期影响雨量、河槽底水量等。这些因素都影响着一次洪水的形成过程,但它们对产汇流的影响并不均衡,不能等同考虑。这几个因素在选择单位线时权重如何来考虑是模糊识别单位线法中的一个难题。本文提出用相关分析的方法统计历次洪水,将各个因素在形成洪水过程中起的作用进行定量计算,从而解决了模糊识别单位线中,权重向量如何确定的问题。     

连续API模型在沂河临沂站径流预报中的应用

洪水模拟和预报对于流域防洪、灌溉和供水等具有重要意义。构建了API模型模拟沂河临沂站流量过程。基于该站2006~2012年(共7 a)的降雨和流量资料,建立了降雨径流相关图,根据时段径流差求得时段净雨量;用瞬时单位线进行汇流计算得到流量过程,并与实测结果进行对比和评定。结果表明,连续API模型在该站模拟效果较好,合格率在70%以上,确定性系数大于0.9,可以用于作业预报。     

Initial Soil Water Content as Input to Field-Scale Infiltration and Surface Runoff Models

Evidence is given of the role of initial soil moisture content, θ _i , in determining the surface runoff hydrograph at field scale, that is a crucial element when distributed models for the estimate of basin response to rainfall have to be formulated. This analysis relies upon simulations performed by a model that, because of the necessity of representing the infiltration of surface water running downslope into pervious saturated or unsaturated areas, uses a coupled solution of a semi-analytical/conceptual approach for local infiltration and a nonlinear kinematic wave equation for overland flow. The model was applied to actual spatial distributions of θ _i , earlier observed over different fields, as well as to a uniform value of θ _i assumed equal to the average value or to the value observed in a site characterized by temporal stability. Our results indicate that the surface runoff hydrograph at a slope outlet is characterized by a low sensitivity to the horizontal heterogeneity of θ _i , at least in the cases of practical hydrological interest. In fact, in these cases the correct hydrograph can be simulated with considerable accuracy replacing the actual distribution of θ _i by the corresponding average value. Moreover, the surface hydrograph is sufficiently well reproduced even though a single value of θ _i , observed at a site anyhow selected in the field of interest, is used. In particular, this extreme simplification leads to errors in magnitude on peak runoff and total volume of surface water with values typically within 10% and 15%, respectively.     

Genetic Algorithm Based Parameter Estimation of Nash Model

Unit hydrograph method is usually used to resolve surface runoff concentration process. Empirical unit hydrograph is sometimes jagged and not smooth because of estimation errors. Owing to the randomicity of correction method, there is some localization in its application. The application of instantaneous unit hydrograph is relatively wider. Generally, moment method is used to estimate the parameters of instantaneous unit hydrograph. However, the error is obvious between the observed flood process and the predicted flood process with moment method, especially near the flood peak. The genetic algorithm toolbox of matlab software is used to optimize the parameters of instantaneous unit hydrograph. The statistical function gamcdf(x, α, β) in matlab toolbox is used to calculate S(t) curve, which can avoid the errors caused by approximate formula method. The case study indicates that the weighted sum of absolute error applying the method in this paper is 25, the result applying moment method is 63, and the result of approximate formula method is 49. The results show that the method in this paper is more effectual than the other two methods.     

基于流量-面积比值的小流域设计洪水计算方法对比研究

为确定分布式模型法、地区瞬时单位线法及推理公式法在估算山区小流域设计洪水过程中的适用性,基于洪峰流量-流域面积比值,以重庆市綦江区蒲河水系为研究对象,采用3种方法分别进行设计洪水计算,并与重庆市实测100 a一遇洪峰流量进行对比。结果表明:①当流域面积＜10 km²时,采用推理公式法更合理可靠;此时河道坡度较大,流域的产、汇流条件符合推理公式法假定条件,计算结果符合实际。②当流域面积为10~100 km²时,分布式模型法与地区瞬时单位线法均可合理计算设计洪水,但前者计算结果比后者更接近实测值。此类流域河道长、坡度平缓,流域的水动力在空间中可视为均匀的扩散;计算格栅单元间连续性强,各栅格向流域出口演算能合理反映真实的设计洪水过程。③当流域面积＞100 km²时,3种方法计算结果与实测值均有不同程度的偏离,但分布式模型法偏离程度最低,可作为设计洪水计算的首选方法。研究结果将有助于合理选择设计洪水计算方法,为类似山区小流域设计洪水计算提供参考。