Quantifying the effects of three-dimensional subsurface heterogeneity on Hortonian runoff processes using a coupled numerical,stochastic approach

The impact of three-dimensional subsurface heterogeneity in the saturated hydraulic conductivity on hillslope runoff generated by excess infiltration (so-called Hortonian runoff) is examined. A fully coupled, parallel subsurface–overland flow model is used to simulate runoff from an idealized hillslope. Ensembles of correlated, Gaussian random fields of saturated hydraulic conductivity are used to create uncertainty in spatial structure. A large number of cases are simulated in a parametric manner with the variance of the hydraulic conductivity varied over orders of magnitude. These cases include rainfall rates above, equal and below the geometric mean of the hydraulic conductivity distribution. These cases are also compared to theoretical representations of runoff production based on simple assumptions regarding (1) the rainfall rate and the value of hydraulic conductivity in the surface cell using a spatially-indiscriminant approach; and (2) a percolation-theory type approach to incorporate so-called runon. Simulations to test the ergodicity of hydraulic conductivity on hillslope runoff are also performed. Results show that three-dimensional stochastic representations of the subsurface hydraulic conductivity can create shallow perching, which has an important effect on runoff behavior that is different than previous two-dimensional analyses. The simple theories are shown to be very poor predictors of the fraction of saturated area that might runoff due to excess infiltration. It is also shown that ergodicity is reached only for a large number of integral scales (∼30) and not achieved for cases where the rainfall rate is less than the geometric mean of the saturated hydraulic conductivity.     

Solving stiff mass transfers in compositional multiphase flow models: Numerical stability and spurious solutions

This paper points out two numerical problems linked to the resolution of compositional multiphase flow models for porous media with the finite‐volume technique. In particular, we consider fluid mixtures featuring fast mass transfers between the phases, hence stiff. In this context, we show how the computation of mass exchange kinetics can be expensive and that erroneous saturation front locations arise. A numerical splitting method is developed which is proven to be stable with advection‐type time steps, whatever the stiffness of the mass transfer. The erroneous front location problem is illustrated and shown to be intrinsically linked to the numerical diffusion. If we assume that the fluids are in thermodynamical equilibrium, we find that spurious solutions can be avoided by deriving and solving a new uncoupled hyperbolic equation for the saturation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Multi-temporal relations between runoff and sediment load based on variable structure cointegration theory

Microscopic and macroscopic multi-temporal correlations between runoff and sediment load were analyzed to reveal the relations between them in the source region of the Yellow River using the complete ensemble empirical mode decomposition with adaptive noise method (CEEMDAN) and cointegration theory. Subsequently, multi-temporal models of runoff and sediment load with structural breaks were developed. The results revealed the following points. (1) The runoff and sediment load relations differed at multi-time scales. Multi-temporal cointegration could reveal the relation between runoff and sediment load at micro scales. (2) A comparison of the original model, composite model 1, and composite model 2 revealed that the multi-temporal cointegration model is better than the original model. (3) The variable structure cointegration model of the runoff and sediment load relation had the highest simulation accuracy, and the smallest average relative error for the simulated runoff was 7.82%. Composite model 2 could more accurately reflect the long-term equilibrium and short-term fluctuating relations between the runoff and sediment load in the source region of the Yellow River.     

铁岭市中心城区降雨径流氨氮污染特征初步研究

为了解铁岭市中心城区降雨形成径流后氨氮污染特征,选取城区内2个典型排污沟为研究对象,采用野外采样与室内分析相结合的方法,利用2005年7月的一场降雨过程实测降雨数据,对氨氮浓度进行对比分析。结果表明:在降雨初期,铁岭市中心城区降雨径流中氨氮浓度迅速上升,并很快达到峰值。随着降雨历时的延长,氨氮浓度逐渐下降并趋于稳定。     

基于树木年轮的贺兰山东麓河流径流量的重建

以采自贺兰山的5个采样点的树轮宽度资料为基础,建立区域标准化年表和差值年表,发现区域差值年表中包含的年径流总量信息多于标准化年表,并最终用区域差值年表序列重建了贺兰山东麓过去259 a的年径流量。相关分析发现降水和温度变化对于树木年轮生长及贺兰山东麓河流年径流总量的形成均有重要影响,是本文从树木年轮重建年径流量的气候水文学基础。校准方程的相关系数为0.638,可解释校准期内年径流总量变化总方差的40.8%,交叉检验的误差缩减值达0.328。分析259 a重建年径流量的变化特征发现:(1)重建流量经历了12个枯水期(1751—1759年,1765—1771年,1788—1802年,1809—1820年,1835—1840年,1847—1855年,1860—1866年,1877—1884年,1899—1908年,1924—1932年,1962—1967年,1980—1994年)和位于其间及1995—2004年的14个丰水期,以平水年份出现最多,但259 a来年径流量的变化较为剧烈。(2)年径流总量出现了持续≥10 a的4次持续枯水期和4次持续丰水期;持续枯水期中以1788—1802年的枯水期强度最大(平均距平百分率-14.9%),而强度第二的持续枯水期(平均距平百分率-10.4%),持续时间也长达15 a(1980—1994年);持续丰水期中以1867—1876年的丰水期强度最大(平均距平百分率+17.9%)。     

基于GIS 分析喀斯特流域下垫面因素对枯季径流的影响——以贵州省河流为例

本文采用GIS 作为空间分析的工具, 分析了喀斯特流域地貌类型等下垫面因素对枯季径流的影响, 并从流域结构的角度, 选择了空间尺度、岩性、地貌类型、森林植被等自然因素作为参数, 借助于SPSS 软件, 运用多元统计学的方法, 建立了多元回归方程数学模型, 对喀斯特流域枯季最小日流量进行预测。      

喜马拉雅山北坡典型高山冻土区冬季径流过程

喜马拉雅山北坡广泛分布着岛状多年冻土,冻土对径流过程有着不可忽视的影响。卡鲁雄曲是该区唯一有常规水文气象观测资料的流域,海拔范围是4 550~7 200 m,其中5 100 m以上为高山冻土区,以下为深层季节冻土区。近20年径流有较明显的增加趋势,为了探明引起径流变化的原因,采用流域内翁果水文站1983—2003年的月径流资料,通过Mann Kendall趋势检验法,Sen坡度估计以及相关统计分析方法,发现寒冷期（11月至次年3月）径流有不同程度的涨幅,发生突变的年份在1990年左右。尤其以1月份最为明显,后10年比前10年增加了67%。遥相关分析表明,1月份径流与7~12月径流有通过95%显著性检验的相关性,它们的共同作用使得径流变化尤为显著,这是冻土区所特有的。     

Hydrologic modeling of the Heihe watershed by DLBRM in Northwest China

Water shortage is a chronic problem in arid Northwest China.The rapid population growth and expanding urbanization as well as potential climate change impacts are likely to worsen the situation,threatening domestic,irrigation,and industrial supplies and even the survival of the ecosystems in Northwest China.This paper describes the preliminary work of adapting the Distributed Large Basin Runoff Model(DLBRM) to the Heihe watershed(the second largest inland river in arid Northwestern China,with a drainage area of 128,000 km2) for understanding distribution of glacial-snow melt,groundwater,surface runoff,and evapotranspi-ration,and for assessing hydrological impacts of climate change and glacial recession on water supply in the middle and lower reaches of the watershed.Preliminary simulation results show that the Qilian Mountain in the upper reach area produces most runoff in the Heihe watershed.The simulated daily river flows during the period of 1990-2000 indicate that the Heihe River dis-charges about 1×109 m3 of water from the middle reach(at Zhengyixia Station) to lower reach,with surface runoff and interflow contributing 51 and 49 percent respectively.The sandy lower soil zone in the middle reach has the highest evapotranspiration rate and also contributes nearly half of the river flow.Work underway focuses on the DLBRM model improvement and incorporation of the climate change and management scenarios to the hydrological simulations in the watershed.     

近50年来中国六大流域年际径流变化趋势研究

应用1950年以来的中国六大流域19个重点控制水文站年径流观测资料,采用MK检验方法研究了中国六大江河的年径流量变化情况。结果表明,近50年来中国六大江河的实测径流量均呈下降趋势。其中海河、黄河、辽河、松花江实测径流量下降明显,严重影响了我国社会经济的发展。