51 年来珠江流域输沙量的变化

根据1955～2005年珠江流域主要水文站的径流量和输沙量数据以及流域降水量数据,对珠江流域输沙量的变化进行了研究,结果发现:(1)石角站(北江)、博罗站(东江)、迁江站(红水河)以及高要站(西江干流)输沙量呈下降趋势,而柳州站(柳江)、南宁站(郁江)的输沙量则呈上升趋势.(2)1955～2005年珠江入海泥沙(石角站、博罗站、高要站输沙量之和)均值为7529×104 t/yr,并在总体上也呈下降趋势.珠江入海泥沙还存在着年际变化上的波动性和阶段性特征,即从1950年代到1980年代呈显著的上升趋势,而此后呈显著下降趋势.通过分析认为:(1)气候变化是造成珠江流域输沙量年际波动性变化的主要因素,但不是造成珠江入海泥沙下降的主要影响因素;(2)珠江流域入海泥沙的阶段性变化特征与水土流失和水土保持相关;(3)水库建设是造成1955～2005年珠江流域入海泥沙减少的主要因素.(4)珠江流域入海泥沙将可能进一步减少,这将对未来珠江河口环境和三角洲的演变产生影响,加强进一步的研究非常必要.

Variation of Sediment Discharge of the Pear l River Basin from 1955 to 2005

Draining at the southern part, the Pearl River is the third largest river in China. The Pearl River is the collective name of West River, North River and East River. Based on long series data (1955-2005) of the water and sediment discharge at the main hydrological stations and the precipitation in the drainage basin, this paper aimed to reveal the variation pattern of the sediment discharge and the causes of the Pearl River. The results are: (1) sediment discharge at Shijiao (North River), Boluo (East River), Qianjiang and Gaoyao (West River) stations show a decreasing trend, while Liuzhou (at Liujiang River, a tributary of West River) and Nanning (at Yujiang River, a tributary of West River) an increasing trend in 1955-2005; (2) the average sediment discharge into the sea from the Pearl River (the sum of the North River, East River and West River) in 1955-2005 is 7529×10⁴ t/yr with a decreasing trend (not significant statistically). The main conclusions are: (1) the variation of precipitation contributed greatly to the yearly fluctuation of the sediment flux, but little to the decreasing trend of the sediment discharge into the sea; (2) the phased variation trend of sediment discharge into the sea is relevant to soil loss and water and soil conservation; (3) dam construction is the main cause of the decrease of the sediment discharge into the sea; and (4) a further decrease of the sediment discharge into the sea may occur in the future decades, which may cause serious environmental problems at the estuary such as slowdown of coastline progradation or even retreat. Further and in-depth study is urgently needed in view of the economic significance of the Pearl River Delta in China and the environmental issues in the estuary, including the coastal region of Hong Kong.