Optimization of a multiple gauge,regulated river‐system model. A system approach

With increasing demands on limited water resources, regulation of larger river systems continues to increase and so too does the need for accurate water accounting and prediction in these systems. River system models are either calibrated manually or automatically on a reach‐by‐reach basis, i.e. each reach is calibrated as a separate entity with little or no consideration of fluxes at other locations within the river system. While this is a practical approach, simulation errors can propagate downstream to make calibration or prediction difficult at those locations. Likewise parameters may suffer from over‐fitting especially where observations are erroneous. We developed and implemented a system calibration strategy in a portion of the Murrumbidgee River, Australia, where parameters for 11 gauges (36 parameters) were calibrated together. Parameter values, model states and model goodness of fit were compared to reach‐by‐reach calibration. The system calibration produced a better goodness of fit across the whole system relative to reach‐by‐reach calibration. Additionally, model system states were more realistic than reach‐by‐reach optimized models. Over‐fitting was obvious using the reach‐by‐reach method for one reach/gauge in particular. This was avoided with system calibration method, with improved goodness of fit at all gauges downstream of the problem gauge. The results here suggest that the system calibration approach provides more hydrologically consistent states, improved overall fit and avoids over‐fitting at problem gauges. Copyright © 2015 John Wiley & Sons, Ltd.     

The effect of climate and land use change on flow duration in the Maryland Piedmont region

This paper describes the use of a continuous streamflow model to examine the effects of climate and land use change on flow duration in six urbanizing watersheds in the Maryland Piedmont region. The hydrologic model is coupled with an optimization routine to achieve an agreement between observed and simulated streamflow. Future predictions are made for three scenarios: future climate change, land use change, and jointly varying climate and land use. Future climate is modelled using precipitation and temperature predictions for the Canadian Climate Centre (CCC) and Hadley climate models. Results show that a significant increase in temperature under the CCC climate predictions produces a decreasing trend in low flows. A significant increasing trend in precipitation under the Hadley climate predictions produces an increasing trend in peak flows. Land use change by itself, as simulated by an additional 10% increase in imperviousness (from 20·5 to 30·5%), produces no significant changes in the simulated flow durations. However, coupling the effects of land use change with climate change leads to more significant decreasing trends in low flows under the CCC climate predictions and more significant increasing trends in peak flows under Hadley climate predictions than when climate change alone is employed. These findings indicate that combined land use and climate change can result in more significant hydrologic change than either driver acting alone. Copyright © 2008 John Wiley & Sons, Ltd.     

Modelling uncertainties in short-term reservoir operation using fuzzy sets and a genetic algorithm / Modélisation d’incertitudes dans la gestion de barrage à court terme grâce à des ensembles flous et à un algorithme génétique

Abstract

Abstract Various uncertainties are inherent in modelling any reservoir operation problem. Two of these are addressed in this study: uncertainty involved in the expression of reservoir penalty functions, and uncertainty in determining the target release value. Fuzzy set theory was used to model these uncertainties where the preferences of the decision maker for the fuzzified parameters are expressed as membership functions. Nonlinear penalty functions are used to determine the penalties due to deviations from targets. The optimization was performed using a genetic algorithm with the objectives to minimize the total penalty and to maximize the level of satisfaction of the decision maker with fuzzified input parameters. The proposed formulation was applied to the problem of finding the optimal release and storage values, taking Green reservoir in Kentucky, USA as a case study. The approach offers more flexibility to reservoir decision-making by demonstrating an efficient way to represent subjective uncertainties, and to deal with non-commensurate objectives under a fuzzy multi-objective environment.     

Optimal operation of reservoirs for downstream water quality control using linked simulation optimization

A methodology is developed for optimal operation of reservoirs to control water quality requirements at downstream locations. The physicochemical processes involved are incorporated using a numerical simulation model. This simulation model is then linked externally with an optimization algorithm. This linked simulation–optimization‐based methodology is used to obtain optimal reservoir operation policy. An elitist genetic algorithm is used as the optimization algorithm. This elitist‐genetic‐algorithm‐based linked simulation–optimization model is capable of evolving short‐term optimal operation strategies for controlling water quality downstream of a reservoir. The performance of the methodology developed is evaluated for an illustrative example problem. Different plausible scenarios of management are considered. The operation policies obtained are tested by simulating the resulting pollutant concentrations downstream of the reservoir. These performance evaluations consider various scenarios of inflow, permissible concentration limits, and a number of management periods. These evaluations establish the potential applicability of the developed methodology for optimal control of water quality downstream of a reservoir. Copyright © 2007 John Wiley & Sons, Ltd.     

不同水力压裂顺序下煤层气井组应力干扰效应研究—以沁水盆地柿庄南区块为例

煤层气井常采用井网布置方式进行开发，不同的水力压裂顺序引起不同的应力干扰效应。为了查明不同水力压裂顺序下煤层气井间应力干扰效应，本文以沁水盆地柿庄南区块3组煤层气井网15口井为研究对象，应用ABAQUS 有限元模拟软件，模拟了煤层气井网中3种水力压裂顺序（先周围后中心、对角、先中心后周围）的应力分布特征及干扰效应，提出了相应的水力压裂顺序建议。结果表明：当施工排量为6.00 8.00 m3/min，液量为430.00 580.00 m3时，（1）先周围后中心、对角、先中心后周围压裂时，距中心井、对角线井、周围井不同距离，依次分为应力释放区、集中区和原始应力区。先周围后中心压裂时，中心井三区范围依次为≤15.00 m、15.00 140.00 m、＞140.00 m。对角压裂时，对角线井三区范围依次为≤60.00 m、60.00 150.00 m、＞150.00 m。先中间压裂时，周围井三区范围依次为≤60.00 m、60.00 144.00 m、＞144.00 m。（2）煤层气井网采用四点法布置，井间距超过300.00 m，可有效避免煤层气井之间的应力干扰。降低煤层气井压裂时的施工难度。     

地震波时域数值优化研究及应用

将最小二乘拟合法与单自由度地震动力反应递归法相结合来解决地震观测和人工模拟地震波过程中速度、位移的基线漂移问题。首先以3次多项式来拟合加速度的均值线(一次优化);再对一次优化后的积分速度、位移时程仍存在的长周期基线波动问题,运用单自由度地震动力反应递归法进行二次优化。文中通过3个数值算例体现出优化算法的优越性,并将优化后的地震波加速度时程应用到江坪河水电站溢洪道控制段三维有限元动力计算分析中。结果表明,该算法消除了积分基线漂移影响,具有较好的可行性、数值稳定性和易操作性。     

地震预测模型优化方法研究

在分析现有基于观测指标“异常-正常”的“二态”地震前兆模式不足的基础上, 提出了异常可表现为多种状态的“多态”前兆模式, 给出“多态”前兆模式下预测效能判定指标, 进一步提出了基于预测效能最优的单项预测模型参数的选择方法。 在广义(时间、 空间、 时-空联合的预测指标)“多态”前兆模式下, 将所建立的模型应用于我国华北和南北带地区, 分别确定了两地区活断层预测地震(M_S≥6)空间分布的最优模型(分别为断层周围20 km、 30 km)及其预测效能(分别为0.42、 0.34)。     

泡沫轻质材料试验研究的均匀设计方法及配方优化

泡沫轻质材料是一种用于岩土工程的新型材料。采用均匀试验设计方法进行材料的配方试验,运用多元非线性回归方法进行方差分析,分析了试验因素的主效应和因素间的交互效应,并建立有约束的非线性规划问题,采用最优化方法进行寻优计算,得出满足工程要求的最优配比。     

煤矿瓦斯抽放的计算机优化和管理平台

服务于高瓦斯矿井的现代化抽放系统应该至少具备 3个条件:合理的抽放技术;先进的抽放设备;以及为完成设备操作和实施抽放技术而制定的各项操作规程、作业规程和相关管理制度。三者之间通过优化实现最佳配置。本文论述了利用计算机技术实现抽放技术优化和抽放管理强化的基本方法,讨论了实现高效瓦斯抽放的技术途径。      

遗传算法和GIS结合进行空间优化决策

资源的有效利用和管理往往涉及到空间的优化配置问题。例如需要在空间上确定n个设施的最佳位置。当选址问题涉及多个目标和不同的约束性条件时,就会变得十分复杂。利用一般的brute-force搜索方法无法对涉及高维数据的问题进行求解。利用遗传算法和GIS结合来解决复杂的空间优化配置问题,具有智能的搜索方法可以大大提高空间的搜索能力。在基于进化的优化过程中,根据GIS的空间数据来计算不同解决方案 (染色体) 的适应度。针对不同的应用目的,GIS可以给出不同的适应度函数。实验表明,所提出的方法比简单的搜索方法和退火算法有更大的优越性。该方法在处理复杂的空间优化问题有更好的表现。