基于连续方程的河道水流双变量耦合演算模型

针对现有的河道水流洪水演算模型只能模拟单一变量(流量或水位)的问题,以水流连续方程和河段蓄水量的两种不同表达形式(蓄水量等于平均过水断面面积与河段长乘积,蓄水量等于河段平均流量与传播时间的乘积)为基础,对马斯京根模型进行了通用性改进,提出了双变量耦合通用演算模型.选取了四大水系(包括内陆河流和入海河流)的16个河段汛期洪水资料进行模型检验,模型验证考虑了地理范围、不同的河段特征和水力特征、洪水量级等因素,全面地检验了模型结构的合理性和模拟实际洪水的有效性.将双变量耦合通用演算模型与传统的马斯京根法进行了效果比较,结果表明双变量耦合通用演算模型的模拟精度高于马斯京根法,模拟效果比马斯京根法稳定一些,而且具有较好的通用性.     

Reverse flood and pollution routing with the lag-and-route model

ABSTRACT

Reverse routing can be used to transfer flood- or pollution-related information monitored at a downstream gauging station to an ungauged upstream cross-section. This signal identification problem is ill-posed and, as such, is sensitive to perturbations in the data to be inverted; therefore, the amplification of errors, e.g., those befalling measurements, must be controlled. Storage routing models are parsimonious diffusion wave substitutes and well suited for conversion to direct reverse routers. We present efficient inversion frameworks based on the lag-and-route (single reservoir plus exact reverse lag-step) and the reservoirs-in-series models. In both cases we invert a centred finite difference scheme of the reservoir storage balance equation that involves only one value of the unknown signal; signal values identified in previous reverse time steps, which would carry perturbations, are absent. This simple structure endows the reverse scheme with robustness. Procedures are verified with perfect and with error-seeded data; solution oscillations caused by the latter are damped by low-pass filtering. Both inverse routing models regain the upstream signals with high fidelity. Reverse storage routing is exemplified in a demonstration of reservoir control and in a field case of solute transport in a stream.

Editor M.C. Acreman; Associate editor X. Chen     

Modelling detention basins measured from high‐resolution light detection and ranging data

The construction of stormwater detention basins is a best management practice to effectively control floods, to provide additional surface storage for excess floodwater and to compensate for the adverse effects of urban development. Traditional field‐based levelling survey methods are very time consuming and subject to human‐induced arbitrariness and error. This article presents an approach to modelling detention basins measured from light detection and ranging remote sensing data. A case study is illustrated by using the White Oak Bayou watershed of Harris County, Texas. The storage–stage curve obtained from the volumetric analysis is used in a modified detention basins routing model, which was developed by adding the weir structure control to the traditional hydrologic reservoir routing equations. The model simulation showed that the peak flow of the synthetic 100‐year reoccurrence event was effectively reduced and delayed by the detention basins. The comparison with the simulation results from the traditional reservoir routing model suggested that previous studies using the reservoir routing model were likely to underestimate the flood reduction effect of detention basins. The sensitivity analysis of the parameters showed that the detention basin design and evaluation should pay more attention on the weir height and river channel's roughness. Copyright © 2011 John Wiley & Sons, Ltd.     

How important is the selection of computational analysis method to the accuracy of rainwater tank behaviour modelling?

As the concept of sustainable urban water management is incorporated into the practice of urban water resource managers, actions, such as the utilization of roof runoff via rainwater tanks, which have multiple benefits, are increasingly being built into urban water systems. Modelling tools are frequently used to predict the yield from rainwater tanks and to estimate the storage capacity required to achieve a given potable supply reduction level, with these estimates used in both urban water resources policy development and engineering design. Therefore, it is important that the accuracy of commonly used models is understood. This paper investigates the impact of computational time step, computational operating rule, initial storage level, and the length of simulation period on the accuracy of the storage–yield–reliability relationship calculated using a simple rainwater tank behaviour model. Four time steps (ranging from 6 min to 24 h), two operational rules (supply before spillage and supply after spillage), two initial storage level states (empty and full), and three simulation periods (50 years, 10 years and 1 year) were applied to a wide range of rainwater tank system configurations and three different locations in Australia. It was found that the supply‐after‐spillage computational operating rule is preferable, while the ratio of the average demand volume in a single computational time step divided by the storage capacity (ΔD/S) can be used to assess whether a given combination of demand, storage, inflow, and computational time step will provide long‐term yield estimates that are within ± 5% of the values produced by a simulation that used a 50‐year time series of climate, 6‐min time step, and a supply‐after‐spillage operational rule (50‐6‐YAS). Copyright © 2007 John Wiley & Sons, Ltd.     

Robust numerical solution of the reservoir routing equation

The robustness of numerical methods for the solution of the reservoir routing equation is evaluated. The methods considered in this study are: (1) the Laurenson–Pilgrim method, (2) the fourth-order Runge–Kutta method, and (3) the fixed order Cash–Karp method. Method (1) is unable to handle nonmonotonic outflow rating curves. Method (2) is found to fail under critical conditions occurring, especially at the end of inflow recession limbs, when large time steps (greater than 12 min in this application) are used. Method (3) is computationally intensive and it does not solve the limitations of method (2). The limitations of method (2) can be efficiently overcome by reducing the time step in the critical phases of the simulation so as to ensure that water level remains inside the domains of the storage function and the outflow rating curve. The incorporation of a simple backstepping procedure implementing this control into the method (2) yields a robust and accurate reservoir routing method that can be safely used in distributed time-continuous catchment models.     

Genetic programming approach for flood routing in natural channels

In recognition of the non‐linear relationship between storage and discharge existing in most river systems, non‐linear forms of the Muskingum model have been proposed, together with methods to calibrate the model parameters. However, most studies have focused only on routing a typical hypothetical flood hydrograph characterized by a single peak. In this study, we demonstrate that the storage–discharge relationship adopted for the non‐linear Muskingum model is not adequate for routing flood hydrographs in natural channels, which are often characterized by multiple peaks. As an alternative, an evolutionary algorithm‐based modelling approach, i.e. genetic programming (GP), is proposed, which is found to route complex flood hydrographs accurately. The proposed method is applied for constructing a routing model for a channel reach along the Walla Walla River, USA. The GP model performs extremely well with a root‐mean‐square error (RMSE) of 0·73 m³ s^?1 as against an RMSE of 3·26 m³ s^?1 for routing the multi‐peaked hydrograph. The advantage of GP lies in the fact that, unlike other models, it establishes the routing relationship in an easy and simple mathematical form. Copyright © 2007 John Wiley & Sons, Ltd.     

Choice of reliability,resilience and vulnerability estimators for risk assessments of water resources systems / Choix d’estimateurs de fiabilité, de résilience et de vulnérabilité pour les analyses de risque de systèmes de ressources en eau

Abstract

Abstract Definitions and estimators of water resources system reliability (the probability that the system will remain in a non-failure state), resilience (the ability of the system to return to non-failure state after a failure has occurred) and vulnerability (the likely damage of a failure event) have been thoroughly investigated. A behaviour analysis addressing monotonic behaviour, overlap and correlation between the estimators was carried out by routing time series of monthly runoff through a reservoir with a specified storage volume that is operated according to a fixed operation policy. Estimation based on historical time series is shown to be problematic and a procedure encompassing generation of synthetic time series with a length of at least 1000 years is recommended in order to stabilize the estimates. Moreover, the strong correlation between resilience and vulnerability may suggest that resilience should not be explicitly accounted for.     

Diffusive approximation for unsteady mud flows with backwater effect

The adoption of the Diffusive Wave (DW) instead of the Full Dynamic (FD) model in the analysis of mud flood routing within the shallow-water framework may provide a significant reduction of the computational effort, and the knowledge of the conditions in which this approximation may be employed is therefore important. In this paper, the applicability of the DW approximation of a depth-integrated Herschel–Bulkley model is investigated through linear analysis. Assuming as the initial condition a steady hypocritical decelerated flow, induced by downstream backwater, the propagation characteristics of a small perturbation predicted by the DW and FD models are compared. The results show that the spatial variation on the initial profile may preclude the application of DW model with a prescribed accuracy. Whenever the method is applicable, the rising time of the mud flood must satisfy additional constraints, whose dependence on the flow depth, along with the Froude number and the rheological parameters, is deeply analyzed and discussed.     

L'Opération Sources en Belgique: premières analyses statistiques des résultats et légitimité des cartes “nitrates”

Abstract

This work critically assesses the storage, or hydrological methods of flood routing, focusing on the Muskingum and Kalinin-Miljukov methods. The common hydraulic basis of these methods and their inter-relationships are established, emphasising hydraulic derivations of the Muskingum method's weighting coefficient. Important characteristics of the routing scheme are highlighted, especially the scheme's affinity to the pseudo-viscosity method of shock computation; the flow-dependence (nonlinearity) of routing parameters is analysed, as are mass balance errors. Options in calculating depths and in handling lateral flows are presented. Storage routing models are shown to be instances of a numerically equivalent convection—diffusion equation or kinematic wave-derived convection—diffusion routing model that is also able to relate depth and discharge at-a-section via loop-shaped rating curves; the consequences of ignoring the rating curves' transience are pointed out. System analytic parameter estimations are summarised, a routing option with direct use of the diffusion wave system response function (SRF) is reviewed, the selection of routing reaches based on the river morphology is discussed, and the extension of storage-type routing to mass transport simulation is indicated.     

Simultaneous identification of parameter,initial condition,and boundary condition in groundwater modelling

In this paper, we perform an inverse method to simultaneously estimate aquifer parameters, initial condition, and boundary conditions in groundwater modelling. The parameter estimation is extended to a complete inverse problem that makes the calibrated groundwater flow model more realistic. The adjoint state method, the gradient search method, and the least square error algorithm are combined to build the optimization procedure. Horizontal two‐dimensional groundwater flow in a confined aquifer is exemplified to demonstrate the correlation between unknowns, the contribution of observation, as well as the suitability of applying the inverse method. The correlation analysis shows the connection between storage coefficient and initial condition. Besides, transmissivity and boundary conditions are also highly correlated. More observations at different location and time are necessary to provide sufficient information. A time series of unsteady head is requested for estimation of storage coefficient and initial condition. Observation near boundary is very effective for boundary condition estimation. The observation at pumping well mostly contributes to the estimation of transmissivity. According to all observations, it is possible to identify parameters, initial condition, and boundary condition simultaneously. Furthermore, the results not only illustrate the traditional assumption of known boundary condition but also initial condition, which may cause an incorrect estimation. Copyright © 2009 John Wiley & Sons, Ltd.     

The effects of controlled drainage on subsurface outflow from level agricultural fields

Daily outflow frequencies and recession curves were used to identify differences in storage–outflow relationships between two different drainage systems, conventional and controlled drainage. A three‐year (1996–1999) field drainage experiment was carried out on a loamy sand soil in southern Sweden. Plots with an area of 0·2 hectares were drained by conventional subsurface drainage (CD) or by controlled drainage (CWT1 and CWT2). The controlled drainage system allowed the groundwater level in the soil to be varied during the year. It was kept at least 70 cm below the soil surface during the growing season but allowed to rise to a maximum of 20 cm below the soil surface during the rest of the year. Measurements were performed to record precipitation, drain outflow and groundwater levels. Daily values of outflow were divided into 10 categories, based on the size of outflow. Recession curves of hourly measurement of outflow were selected. They behaved like single reservoirs and a linear storage–outflow model was applied. Least squares estimates of the parameters initial outflow, initial storage volume and retention constant were calculated. Controlled drainage had a significant effect on total drain outflow and outflow pattern during the three years of measurement. The total drain outflow was 70% to 90% smaller in CWT than in CD. The analysis revealed that the initial outflows were higher, the retention constant and the temporary storage lower in CWT. The hydrological impacts of the reduction in temporary storage were higher peak flow, shorter lag time and shorter recession time and these effects increased with an increased groundwater level. Copyright © 2003 John Wiley & Sons, Ltd.     

应用GPS数据和Slepian基函数反演川云渝地区陆地水储量变化

局部Slepian函数是将局部区域内的地球物理信号转化为空间谱的一种方法,其可以保证在球面上局部范围内获得最优谱平滑解,非常适用于局部范围地球物理信号的研究.本文利用中国陆态网西南地区72 个测站的连续GPS观测资料分析川云渝地区陆地水负荷形变特征,并基于Slepian函数方法解算 60 阶的空间谱基函数,结合弹性质量...     

Enhancement of the channel routing module in SWAT

The objective of this study is to demonstrate that the channel flow routing techniques used in the Soil and Water Assessment Tool (SWAT) can be sometimes inappropriate for runoff simulation in small basins. Simulated hydrographs have a tendency to underestimate peak flows or may send a false signal during the recession periods when SWAT is applied to the Mihocheon Basin in South Korea. This was particularly evident for sub‐basins that had a short travel time of much less than a day. In order to enhance the channel routing module in SWAT, an alternative routing technique in which Manning relationship is combined with a simple channel reach continuity equation is proposed in the present study. The advantage of the proposed routing technique is that parameters are readily available from channel morphological data and that it is applicable to small basins. Through simulations of specific events, this routing module that is incorporated into SWAT is almost free from instability errors and produces realistic flow depths and velocities unlike the original version of SWAT with Muskingum method. Copyright © 2009 John Wiley & Sons, Ltd.     

淮河具有行蓄洪区河系洪水预报水力学模型研究

针对淮河流域河系特点,建立淮河具有行蓄洪区河系洪水预报模型.干流河道洪水演进采用一维水动力学模型,钐岗分流量利用分流曲线法推求,利用虚拟线性水库法解决大洪水时支流洪水受干流顶托作用,临淮岗闸作为水力学模型的内边界条件进行处理,利用分流比法概化行洪过程,行洪区内只有蓄满时,才会有出流,行洪区内的洪水利用Muskingum...     

A single recovery type curve from Theis'' exact solution

The Theis type curve matching method and the Cooper-Jacob semilog method are commonly used for estimation of transmissivity and storage coefficient of infinite, homogeneous, isotropic, confined aquifers from drawdown data of a constant rate pumping test. Although these methods are based on drawdown data, they are often applied indiscriminately to analyze both drawdown and recovery data. Moreover, the limitations of drawdown type curve to analyze recovery data collected after short pumping times are not well understood by the practicing engineers. This often may result in an erroneous interpretation of such recovery data. In this paper, a novel but simple method is proposed to determine the storage coefficient as well as transmissivity from recovery data measured after the pumping period of an aquifer test. The method eliminates the dependence on pumping time effects and has the advantage of employing only one single recovery type curve. The method based on the conversion of residual drawdown to recovered drawdown (buildup) data plotted versus a new equivalent time (delta(t) x t(p)/t(p) + delta(t)). The method uses the recovery data in one observation point only, and does not need the initial water level h0, which may be unknown. The accuracy of the method is checked with three sets of field data. This method appears to be complementary to the Cooper-Jacob and Theis methods, as it provides values of both storage coefficient and transmissivity from recovery data, regardless of pumping duration.     

Coupling water flow and solute transport into a physically-based surface-subsurface hydrological model

A distributed-parameter physically-based solute transport model using a novel approach to describe surface-subsurface interactions is coupled to an existing flow model. In the integrated model the same surface routing and mass transport equations are used for both hillslope and channel processes, but with different parametrizations for these two cases. For the subsurface an advanced time-splitting procedure is used to solve the advection-dispersion equation for transport and a standard finite element scheme is used to solve Richards equation for flow. The surface-subsurface interactions are resolved using a mass balance-based surface boundary condition switching algorithm that partitions water and solute into actual fluxes across the land surface and changes in water and mass storage. The time stepping strategy allows the different time scales that characterize surface and subsurface water and solute dynamics to be efficiently and accurately captured. The model features and performance are demonstrated in a series of numerical experiments of hillslope drainage and runoff generation.     

Conceptual modelling to assess the influence of hydro-climatic variability on runoff processes in data scarce semi-arid Andean catchments

Using hydro-meteorological time series of 50 years and in situ measurements, the dominant runoff processes in perennial Andean headwater catchments in Chile were determined using the hydrological model HBV light. First, cluster analysis was used to identify dry, wet and intermediate years. From these, sub-periods were identified with contrasting seasonal climatic influences on streamflow. By calibrating the model across different periods, impacts on model performance, parameter sensitivity and identifiability were investigated, providing insights into differences in hydrological processes. The modelling approach suggested that, independently of a dry or wet period of calibration, the streamflow response is mostly consistent with flux from groundwater storage, while only a small fraction comes from direct routing of snowmelt. The variation of model parameters, such as the groundwater rate coefficient, was found to be consistent with differing recharge in wet and dry years. The resulting snowmelt–groundwater model is a realistic hypothesis of the hydrological operation of such complex, data scarce and semi-arid Andean catchments. This model may also be a useful tool for predictions of seasonal water availability and a basis for further field studies.     

BIBLIOGRAPHY—BIBLIOGRAPHIE

Abstract

The Coupled Routing and Excess STorage model (CREST, jointly developed by the University of Oklahoma and NASA SERVIR) is a distributed hydrological model developed to simulate the spatial and temporal variation of land surface, and subsurface water fluxes and storages by cell-to-cell simulation. CREST's distinguishing characteristics include: (1) distributed rainfall–runoff generation and cell-to-cell routing; (2) coupled runoff generation and routing via three feedback mechanisms; and (3) representation of sub-grid cell variability of soil moisture storage capacity and sub-grid cell routing (via linear reservoirs). The coupling between the runoff generation and routing mechanisms allows detailed and realistic treatment of hydrological variables such as soil moisture. Furthermore, the representation of soil moisture variability and routing processes at the sub-grid scale enables the CREST model to be readily scalable to multi-scale modelling research. This paper presents the model development and demonstrates its applicability for a case study in the Nzoia basin located in Lake Victoria, Africa.

Citation Wang, J., Yang, H., Li, L., Gourley, J. J., Sadiq, I. K., Yilmaz, K. K., Adler, R. F., Policelli, F. S., Habib, S., Irwn, D., Limaye, A. S., Korme, T. &; Okello, L. (2011) The coupled routing and excess storage (CREST) distributed hydrological model. Hydrol. Sci. J. 56(1), 84–98.     

Generation and regulation of summer runoff in a boreal flat fen

Hydrometric measurements, electrical conductivity, water isotopic and hydrochemical components of stream water were used to study summer runoff generation in a flat fen. Different processes generated runoff at low- and high-flows. At storm-flows, fen runoff was generated from overland flow, originating from upland surface water. Temporary storage of water on the fen surface attenuated and delayed flow peaks. At low-flows, runoff at the fen outlet was generated from shallow subsurface flow in the Acrotelm. During low-flow periods, water originated mainly from peat storage water while during episodic events the wetland water storage was renewed by inflowing stream water. Assessment and modeling of hydrological effects of peatlands should be performed separately for low-flows and high-flows, based on the dominating runoff generating processes. Attenuation and retardation of storm-flows in fens by temporary surface storage will depend on the geometric properties of both storage sections and sections controlling outflow. A routing reservoir model adapted for flat fens can be used for simulation of attenuation and retardation in runoff events, and it is suggested that the model concept should be tested for a broader range of peatlands.     

Unified structural approach to linear flood routing

The structural theory of linear systems, which allows the non-homogeneous initial and boundary conditions to be expressed as part of a generalised system input, is applied to the problem of linear flood routing. The standardising functions needed to accomplish this are derived for three methods of lumped hydrologic flood routing (lag and route, Muskingum and Kalinin-Milyukov) and to three methods of distributed hydraulic flood routing (kinematic wave and two simplified forms of the linear St. Venant model). The appropriate Green's functions needed to complete the solution for these six cases are also presented.