三江平原挠力河流域地下水流数学模型的建立及仿真

以三江平原挠力河流域作为研究对象,根据挠力河流域的地质和水文地质资料,建立了挠力河流域水文地质概念模型.在水文地质概念模型的基础上,建立了挠力河流域地下水三维数学模型,并采用国际通用的地下水数值模拟软件Visual Modflow进行求解.用改进BP神经网络模型预报降水量和蒸发量,用Elman小波神经网络预报地下水开采量,实现确定性模型和随机模型的耦合,建立了地下水确定性-随机耦合模型.采用该模型对2020年挠力河流域地下水位流场进行预测.结果表明,2007-2020年挠力河流域地下水系统水位平均降深1.48 m,平均年降深0.1057 m.     

地下水数值模拟中的参数随机模拟

从水文地质参数的随机性出发,以滦河某拟建水源地为例,采用地下水数值模拟软件GMS建立了参数随机模拟的数值模型,并求得模型的随机解,计算出模型的水位均值流场和水位标准差分布.结果表明:在模拟非均质含水层二维流动问题中,充分考虑渗透系数和给水度的随机特性的蒙特卡罗法预测结果可靠,比确定性方法更加科学、有效.     

淄博市地下水水位动态分析

在对淄博市地下水的径、补、排条件及地下水水位动态特征和地下水水位的变化情况进行分析评价的基础上,建立了地下水位与开采量、降水量的二元非线性回归模型,并进行了模拟精度分析.结果表明:该模型用于地下水水位与地下水开采量、降水量之间定量关系的分析,符合实际,适用性好,可作为对淄博市地下水多年动态进行预测的一种方法.     

北方浅层地下水超采区地下水预测模型

针对北方地区地下水动态特征,选定河北省大清河地下水系统的大沙河-磁河冲洪积扇孔隙地下水系统小区作为研究区。研究区地下水动态主要受降水影响,年内变化较大,根据这一特点,利用神经网络等工具建立了研究区浅层地下水分月地下水预测模型。模型采用1991年-2000年数据进行参数率定,采用2001年-2005年数据对模型进行了验证。通过该模型的建立,解决了北方地下水预测中预测精度差、模型不稳定的难题,为水资源管理提供了科学依据,为其他类似地区地下水动态预测奠定了坚实的基础。     

RD预报模型在渠井结合灌区地下水位动态预测中的运用

陕西省泾惠渠灌区是一个典型的渠井结合灌区。以Visual Modflow地下水数值模拟软件为开发平台,在建立的灌区地下水数值模型的基础上,利用时间序列及神经网络等理论,建立了基于随机——确定(random-determination简称RD)耦合方法的地下水预报模型,并对灌区未来10年的地下水位动态进行了分析和预测,以指导灌区未来地下水资源可持续开发利用。     

地下水动态预测方法分析

地下水作为水资源的重要组成部分,在工农业生产和居民生活中发挥着重要的作用。地下水动态预测就是为合理开发利用地下水资源提供科学的管理依据。本文介绍了地下水动态预测的主要工作步骤;地下水动态预测模型分类及特点;各种模型相应的求解方法及其对比分析和适用范围。在应用过程中,要在累积观测资料的基础上根据具体情况选择适合的模型及方法去进行分析预测,从而使预报精度达到理想效果。     

SDP—DDP模型在水资源系统规划中的应用

本文针对单一水库的水资源综合利用规划问题,提出并建立了随机动态规划与确定性动态规划相结合的SDP-DDP数学模型。该模型用马尔可夫过程来描述径流随机过程。并在流量系列相关的条件下推求转移概率,在策略达到稳定的条件下用迭代法推求稳态联合概率。然后在此基础上用随机动态规划来决策具有水文上不确定性的来水状态和蓄水状态某种组合的决策放水量R_(kit),再用确定性的动态规划对R_(kit)在各用水户之间进行最优分配,使得系统目标效益最大。该模型以云南昭通地区渔洞水库为研究实例,成功地解决了渔洞水库综合利用的规划问题,通过经济分析,在四个可行方案中选出了最佳方案。     

土壤非均匀水流运动与溶质运移的两区-两阶段模型

根据优先流发展过程中所表现出来的阶段性特征和分形特征,建立了描述非均匀土壤水流运动和溶质运移过程的两区-两阶段模型。模型认为,研究区域可划分为水流经过的活动流场(即优先流流场)和水流绕过的不活动流场两个区域;优先流流场在发展过程中将先后经历流场扩张和保持两个阶段;处于扩张阶段的优先流流场,其内部土壤水流运动的快速非平衡特征明显,并表现出明显的分形特征;处于保持阶段的优先流流场,其内部的土壤水流运动类似于基质流运动,无明显的分形特征。通过在砂土、壤土和黏土条件下开展的6个示踪试验,检验和评价两区-两阶段模型、活动流场模型和两区模型模拟预测非均匀土壤水流运动和溶质运移的有效性。研究结果表明,两区-两阶段模型可较好地描述各种土质条件下的优先流运动;活动流场模型对壤土和黏土条件下的优先流运动预测精度较好,而对砂土条件下的优先流预测精度较差;两区模型对各种土质条件下的优先流运动预测精度均较差。     

SWAT模型与MODFLOW模型的耦合计算及应用

为了准确模拟区域地下水动态变化,将地表水SWAT模型与地下水MODFLOW模型进行耦合计算。根据SWAT分布式模型的特点,以其水文响应单元(HRU)和MODFLOW模型的有限差分网格(cell)作为基本交换单元,将SWAT模型计算的地下水补给量和潜水蒸发量引入MODFLOW模型的地下水补给(RCH)模块和潜水蒸发(EVT)模块中,并将其应用于徐州市张集地区的地下水模拟计算。结果表明,SWAT模型与MODFLOW模型的耦合计算能准确模拟和预测该地区的地下水水情及其地表水和地下水之间的相互作用。     

阿克苏地下水资源评价与可持续利用研究

根据阿克苏地区地质、水文地质条件和地下水环境状况,建立了地下水系统概念模型和数值模型.利用地下水长系列动态资料对数值模型进行了识别和验证,利用验证后的模型对阿克苏地下水资源进行了评价和预测,在此基础上对阿克苏水资源合理开发利用提出了合理化建议.     

基于组合赋权模糊云理论的高边坡稳定性评价

针对高边坡稳定性评价中指标赋权及其模糊隶属度等不确定问题,提出了一种基于组合赋权模糊云理论的高边坡稳定性评价方法。通过构建多因素协同驱动的高边坡稳定性评价指标体系及其等级划分标准,综合利用梯层指标的主客观组合赋权方法,并考虑到评价中的模糊性和随机性特点,引入模糊熵和云理论,建立了适应于高边坡稳定性多维评价梯级云模型。最后应用于锦屏Ⅰ级水电站左岸边坡的稳定性评价,对比分析了不同评价方法的计算结果,从而佐证了文中提出方法的有效性。     

有限深两层流体中内孤立波传播演化理论模型研究

该文对Choi和Camassa给出的一个内孤立波方程模型中的系数进行了修正,并给出了基于方程的内孤立波定态解表达式,将其称为内孤立波me Kd V理论解,进而采用有限体积/有限差分混合方法数值求解内孤立波的三类(Kd V、e Kd V和me Kd V型)非线性传播演化方程,分别以内孤立波的Kd V、e Kd V、MCC和me Kd V定态解作为初始输入波,研究其非线性传播演化特性,并获得其适用性条件。结果表明,三类非线性传播演化方程,只适合于相应内孤立波定态解初始波的定态传播,而对其他定态解初始波将发生波形变形、分裂等非线性现象。在此基础上,定量地给出了三类非线性传播演化方程的适用性条件,为采用何种非线性方程来研究实际海洋中内孤立波的传播演化问题提供了理论依据。     

土壤水分特征曲线模型对数值模拟非饱和渗流的影响

土壤水分特征曲线直接影响非饱和渗流场压力水头和含水率的预测结果。Brooks-Corey模型和van Genuchten模型是目前运用最广泛的土壤水分特征曲线模型。本文给定三种不同质地土壤(粘土、砂土和砾石)的BC模型参数,根据Morel提出的BC模型与VG模型等价的参数关系计算出VG模型参数。采用上述两模型分别对这三种土壤进行了均质土柱的入渗过程模拟。两种模型的计算结果有一定差别。三种土壤土柱的VG模型湿润锋推进速度都比BC模型大。由于粘土的初始含水率接近饱和,BC模型和VG模型的渗流场差距最大。粘土土柱上表面压力水头的变化幅度BC模型小于VG模型,而含水率的变化幅度BC模型大于VG模型。砂土和砾石土柱上表面压力水头和含水率的变化幅度都为BC模型大于VG模型。砂土土柱BC模型和VG模型的渗流场差距随入渗时间的持续而加剧。     

Planning of Groundwater Supply Systems Subject to Uncertainty Using Stochastic Flow Reduced Models and Multi-Objective Evolutionary Optimization

The typical modeling approach to groundwater management relies on the combination of optimization algorithms and subsurface simulation models. In the case of groundwater supply systems, the management problem may be structured into an optimization problem to identify the pumping scheme that minimizes the total cost of the system while complying with a series of technical, economical, and hydrological constraints. Since lack of data on the subsurface system most often reflects upon the development of groundwater flow models that are inherently uncertain, the solution to the groundwater management problem should explicitly consider the tradeoff between cost optimality and the risk of not meeting the management constraints. This work addresses parameter uncertainty following a stochastic simulation (or Monte Carlo) approach, in which a sufficiently large ensemble of parameter scenarios is used to determine representative values selected from the statistical distribution of the management objectives, that is, minimizing cost while minimizing risk. In particular, the cost of the system is estimated as the expected value of the cost distribution sampled through stochastic simulation, while the risk of not meeting the management constraints is quantified as the expected value of the intensity of constraint violation. The solution to the multi-objective optimization problem is addressed by combining a multi-objective evolutionary algorithm with a stochastic model simulating groundwater flow in confined aquifers. Evolutionary algorithms are particularly appropriate in optimization problems characterized by non-linear and discontinuous objective functions and constraints, although they are also computationally demanding and require intensive analyses to tune input parameters that guarantee optimality to the solutions. In order to drastically reduce the otherwise overwhelming computational cost, a novel stochastic flow reduced model is thus developed, which practically allows for averting the direct inclusion of the full simulation model in the optimization loop. The computational efficiency of the proposed framework is such that it can be applied to problems characterized by large numbers of decision variables.     

砂槽模拟浅源热泵的合理井间距及布局优化——以枫林九溪为例

针对西安市地下水源热泵抽灌井群的设计未形成一定的标准和规范,以西安国际港务区迎宾大道高新地产枫林九溪地下水源热泵系统为例,通过建立室内物理砂槽模型,模拟地下水源热泵的实际运行过程,利用温度传感器监测在模拟运行过程中砂槽内部温度随流量和井间距变化而产生的变化。结果表明:砂槽模型下的模拟距离与现实中安全距离基本一致,验证了砂槽模型的可行性和可靠性;同等条件下"直线异侧布局"和"三角布局"较"直线同侧布局"和"扇形布局"更不容易发生热突破。     

ECO-HYDRAULICS TECHNIQUES FOR CONTROLLING EUTROPHICATION OF SMALL SCENERY LAKES-A CASE STUDY OF LUDAO LAKE IN SHANGHAI

The Ludao Lake with an area of 0.86 km2 and 50% water surface ratio, was taken as an example to study the eco-hydraulics techniques for preventing lake eutrophication. Besides external water inflow and outflow, the term related to internal local flow circulation was added in the continuity equation of two-dimensional horizontal hydrodynamic model, and further the hydrodynamic model was calibrated by the scenario of no water exchange. The velocity of 0.2 m/s was suggested to be the critical velocity of controlling algal bloom. To achieve the critical velocity in the whole lake, three factors were analyzed, which are wind, artificial external inflow augmentation and internal local flow disturbance by pump circulation. It is found that the role of wind can be disregarded. For the eco-hydraulics technique of external lake water inflow augmentation, the water flowing route should be firstly optimized, further, the lake inflow has a critical value under specified water level due to the narrow inlets, so the whole lake is difficult to reach the critical velocity to prevent algal bloom, and a combination of external inflow augmentation and internal local flowing disturbance should be considered. Simulation results show that the combination of external water inflow augmentation and internal local flow disturbance requires less eco-flow to achieve the global critical velocity than the sole internal local flow disturbance, for the Ludao Lake, the former requires total eco-flow of 25 m3/s, which reduces by 50% than the latter requiring total eco-flow of 52 m3/s.     

Stochastic and Robust Multi-Objective Optimal Management of Pumping from Coastal Aquifers Under Parameter Uncertainty

Combined simulation-optimization approaches have been used as tools to derive optimal groundwater management strategies to maintain or improve water quality in contaminated or other aquifers. Surrogate models based on neural networks, regression models, support vector machies etc., are used as substitutes for the numerical simulation model in order to reduce the computational burden on the simulation-optimization approach. However, the groundwater flow and transport system itself being characterized by uncertain parameters, using a deterministic surrogate model to substitute it is a gross and unrealistic approximation of the system. Till date, few studies have considered stochastic surrogate modeling to develop groundwater management methodologies. In this study, we utilize genetic programming (GP) based ensemble surrogate models to characterize coastal aquifer water quality responses to pumping, under parameter uncertainty. These surrogates are then coupled with multiple realization optimization for the stochastic and robust optimization of groundwater management in coastal aquifers. The key novelty in the proposed approach is the capability to capture the uncertainty in the physical system, to a certain extent, in the ensemble of surrogate models and using it to constrain the optimization search to derive robust optimal solutions. Uncertainties in hydraulic conductivity and the annual aquifer recharge are incorporated in this study. The results obtained indicate that the methodology is capable of developing reliable and robust strategies for groundwater management.     

Probability model for gravel sediment entrainment in turbulent flows

This paper reports a stochastic model for the prediction of rollover movement probability of gravel particles in turbulent flow. The model is based on the data of a Direct Numerical Simulation of turbulent flow over a rough bed, which is represented by one layer uniform sphere particles. The locations of effective drag and lift forces are explored, as well as the ratio of drag and lift coefficients. The comparison between rollover and pickup probability models indicates that pickup model is valid for cases of critical shear stress less than 0.1 while rollover model works for critical shear stress larger than 0.1. Thus it is reasonable to take into consideration of both of the two models to predict sediment transport behavior in turbulent flows, especially for fluvial rivers which contain different kinds of sediment particles.     

Multi-objective stochastic groundwater management of nonuniform,homogeneous aquifers

Like any other resources planning and management, groundwater management is performed in a stochastic environment in which the system itself involves a number of random elements. Consequences as a result of decisions made based on analyses are not certain. This paper presents a management model using the chance-constrained framework which explicitly considers the random nature of aquifer properties. The model enables the derivation of an optimal groundwater management policy that would satisfy required operation performance reliability. Furthermore, the chance-constrained model is extended to the multi-objective optimization framework in which a tradeoff between total water supply pumpage and system performance reliability is explicitly considered. The models are applied to a hypothetical example of a steady, nonuniform, homogeneous confined aquifer.     

非参数解集模型及其在水文随机模拟中的应用

解集模型是水文随机模拟的重要工具之一，它能保持总量与分量、分量与分量在时间尺度或空间尺度上的方差、协方差结构和其它统计特性。传统解集模型是对序列相依结构和概率密度函数形式作某种假定后用参数来描述的，因而有其自身的缺陷。文献［１］提出的非参数解集模型就避开了上述假定，克服了传统解集模型的不足。本文介绍非参数解集模型并应用于金沙江流域屏山站月径流随机解集。研究结果表明该模型适合于水文随机模拟。