石羊河流域武威盆地地下水系统的管理模型

武威盆地位于祁连山北麓,河西走廊东段,腾格里沙漠西侧,是一个历史悠久的农业灌溉盆地。本文针对该区由于不合理开发水资源所引起的生态环境问题,采用系统工程的思想和方法,应用地下水系统管理模型确定地下水系统的最优开采方案,以使地下水的开采在取得最大经济效益的同时,保持良好的生态环境和社会环境。论文通过地下水系统的目标分析、环境分析、结构分析和模型化,确立了盆地地下水系统管理的目标、自然环境、技术经济环境和社会环境约束条件,校正了地下水系统的数值模型。在此基础上,用响应矩阵法把地下水系统的数值模型与最优化模型藕合起来,建立了盆地地下水系统的管理模型。通过运转管理模型,获得了盆地地下水的最优开采方案,为地下水合理开发利用,提供了科学依据。

GROUNDWATER SYSTEM MANAGEMENT MODELLING OF WUWEI BASIN IN SHIYANG RIVER CATCHMENT

Wuwei basin, located in the northwest of China, consists of several river alluvial fans. It is bounded by the Qilian mountains in the south and southwest and by the Dongda and Longshou mountains in the north. It extends to the Tenggeli desert in the east. The area of the basin, which is not covered by desert, is about 4,000 km2. The basin is one of the most important agricultural bases in the northwest of China. The agriculture depends completely on the irrigation since in the area there is very little rainfall, about 100-200 mm/a, and very large evaporation, about 1900-2700mm/a. The water sources for irrigation are from the rivers, which stem from the Qilian mountains, and the groundwater. In the past 10 years, the groundwa-ter levels in the basin were continuously decreasing with the increasing groundwater abstraction for agricultural irrigation. As a consequence, some ecological and environmental problems, such as salinization and desertification, have occurred. Therefore, an optimal groundwater pumping strategy needs to be designed for the basin to get maximum groundwater for irriga- tion, where, at the same time, the ecological environment must be kept in good condition.A distributed parameter groundwater management model based on the response matrix approach was applied to solve the optimization problem. In the ideal case, the optimization of the groundwater pumping strategies includes the following aspects:establishment of the objectives; identification of the constraints; optimization of the alternatives; choice of the optimum.All those aspects should be included into a groundwater management model. However, this is always too complicated to be executed in practice. Instead, a sub-optimal procedure is carried out by integrated use of systems analysis and groundwater management modelling. In this procedure, systems analysis is employed to analyze the various aspects related to groundwater management, and the groundwater management model is used to optimize the designed alternatives.An optimal groundwater pumping strategy was determined for the basin using the procedure. In the study, first a finitedifference groundwater model with polygon cells was calibrated and later used to generate the response matrix of the basin and to simulate the so-called "additional drawdown". All the aspects, such as the groundwater usage, watet resources components and their relations, impacts of groundwater pumping on ecology and environment, conjunctive use of the groundwater and surface water etc., are analyzed to establish the objective and to identify the constraints for the management model. Two alternative groundwater pumping strategies were designed and optimized. An optimal strategy was chosen after evaluation of the alternatives.In the final discussion, some suggestions were recommended to the water authority, and it is pointed out that the integrated use of systems analysis and the groundwater management model is suitable for solving the large scale, complicated groundwater resources management problem.