摘要
大型水利工程的建设,使人类能够对水资源进行更为有效的管理和充分的利用,但同时不可避免的带来了一系列的环境问题。为弥补或减缓水库建设对生态环境的影响,探求考虑水质目标的水库优化调度方式具有重要的实践意义。
本文以三峡库区支流香溪河为背景,研究了水库调峰运行方式对河流水质的影响,建立水质智能预测模型并应用到水库优化调度中。主要包括以下内容:
1.建立二维非恒定流水动力模型。采用有限单元法离散研究区域,预测了三峡水库坝前水位175m时的库区流场。并且在计算不同运行方式下库区流体动力场的基础上,通过水位、流速、流量的变化过程对比分析,得出结论:调峰运行可以显著增强库区和支流的水位波动,促进水体交换。
2.建立香溪河一维水质模型。在总结三峡调峰运行下香溪河水质浓度变化规律的基础上,确定了支流污染物迁移扩散的影响因素,并通过引入水质速率描述水质变化,分析了谷荷流量、调峰流量、坝前水位及浓度边界对支流水质的影响程度。
3.建立香溪河水质预测模型。在一维水质模拟基础上,应用改进的BP神经网络算法,对大量典型工况样本数据进行训练和误差分析,建立稳定性好、精度高的水质预测模型。
4.建立基于水质智能预测的水库优化调度模型。在明确三峡水库优化调度原则、目标及多种约束条件的基础上,建立了基于水质预测的三峡水库优化调度模型,并采用遗传算法寻优求解。通过分析以发电量、水质改善为目标的优化调度运行方式对支流水质的影响,最后确定三峡非汛期综合效益最大的水库优化调度运行方案。
The management and utilization of water resources are improved more and more scientifically and effectively through numerous constructions of water conservancy. However, these constructions also bring series of environmental problems. In order to decrease and clear those impacts on the environment, plenty of studies have been focused on this field, which makes great sense to the research of reservoir optimal operation which focused on water quality.
This paper is mainly based on a real watershed management instance - Xiangxi River which is located in Three Gorges Region. The objective of this study is to establish an effective prediction model for simulation the river water quality change together with reservoir optimal operation. The main contents of this research are as follows:
1. Generate 2-Dimensional hydrodynamic numerical model.
In this model the finite element method is used to generate a study area, and water dynamic models are used to predict basic fluid dynamic fields when Three Gorges Dam’s water level evaluates up to 175m. Hydrodynamic characteristics are also analyzed by calculating fluid dynamic field under different operation modes. At last a conclusion is got that peak regulation can enhance water level fluctuation in reservior and branch region and also can improve water exchange.
2. Generate 1-Dimensional water quality model.
In this model we get a summary of concentration change law of Xiangxi River water quality under Three Gorges Powerplant’s different peaks. And water quality change rate is introduced to describe water quality change, after that make certain the factors and their weights on pollutant transpiration/diffusion in tributary rivers which is caused by Three Gorges. Also valley load flow, peak regulation, level in front of dam and concentration boundary impacts on branch water quality are analyzed in depth.
3. Water quality prediction model is formed by using improved Backward
Propagation Artificial Neural Network(BP-ANN) algorithm whose samples come from characteristic real data, and its model is based on sample training and error analysis. As a result, we get a stable and high precision model.
4. Reservoir optimal operation model based on water quality intelligent prediction is established.
Based on Three Gorges Dam's Reservior optimal operation principle, objective and multiple constraints the water quality pridiction model is established. And Genetic algorithm is used in this model to get a solution. Through analyzing the optimal operation's impacts on water quality based on the aim of improving electricity generation and water quality, the reservoir optimal operation scheme is achieved to maxmize the comprehensive benefits when in non-flood season.
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