长江大通-河口段枯季的径流量变化

通过实地调查和收集长江下游1950－2000年水文、水利工程资料，建立了长江大通以下枯季径流量变化地理信息系统，分析了影响长江大通水文站以下径流量变化的水文过程，探索了这一区间枯季径流量变化的成因与过程。调查研究表明，截止2000年大通以下各类抽引水工程的总数已达64个，抽引水能力达到了4626m^3/s（潮周期内平均轴引水流量）。实际抽引水量呈现很大的年、季波动，这与本区气候干旱情况、农作物生长期、跨流域调水量等多种因素有关。研究表明：大通－河口段沿江两岸大量的抽引水已成为影响长江大通以下枯季入海流量变化的最重要的因素。本文在过去实际抽引江水资料的基础上，估算了过去不同水文、气候背景下长江大通以下枯季径流量的变化幅度及其对入海流量的影响，并利用实际数据进行了验证。在此基础上，探讨了未来长江大通以下枯季的径流量变化趋势。

Changes of Water Discharge between Datong and the Changjiang Estuary during the Dry Season

Based on data from hydrometric stations and other documented sources about the hydro-engineering works downstream from Datong (the tidal limit from the East China Sea), this paper presents a preliminary study on water discharge changes between Datong and Xuliujing during the dry season. The natural hydrological processes and human factors that influence the changes of water discharge are analyzed with the help of the GIS technology. The investigations indicate that the water-extracting engineering projects downstream Datong had totaled to 64 in number by the end of 2000, with a water-extraction capacity up to 4626 m 3 /s averaged in a tidal cycle. The water abstractions from the Changjiang River downstream Datong have become the most important agent that may cause large and episodic drop in water discharge downstream Datong during dry season. The potential magnitude in water discharge changes under different climatic and hydrological conditions in dry season and its influence on the discharge into the sea are estimated based upon records of water extractions and parameters of engineering capacity. The results were calibrated with the actual data. The future trend of changes in water discharge to the sea during the dry season was discussed according to the historical data and the newly built engineering projects. The results show that the water extractions in dry season before 2000 downstream Datong had exerted remarkable impacts on discharges into the sea only during the extremely dry year like the period 1978-1979, when the monthly mean discharges all decreased over 490 m 3 /s. The decrease in January and February accounted for about 7% of the total discharge recorded at Datong. It is expected that the water extractions will continually increase in the coming decades, especially during dry years, and will have a far-reaching effect on the changes of water discharge from the Changjiang into the sea. The decrease in monthly mean water discharge is estimated to be over 1,000 m 3 /s.