大量采沙对东江下游及东江三角洲河道低水位的影响

Influences of sand excavation on low water level in the lower reaches and delta of Dongjiang River

计算了1964～2003年东江下游及东江三角洲的主要水文（位）站不同保证率的低水位.结合采沙情况对比分析表明,处于常年径流为主河段上的惠阳站、博罗站,20世纪80年代初至今低水位呈持续下降趋势;处于感潮河段上的樊屋站、石龙站和大盛站,90年代以后低水位均略有不同程度地上升.低水位较大幅度下降主要原因是,河床大量采沙导致河槽容积增大、河床高程明显降低;而河床地形变化引起的三角洲河网区潮汐动力增强,则是感潮河段低水位上升的主要原因.

The low water levels at some hydrologic stations in the lower reaches and delta of the Dongjiang River with different assuring probabilities from 1964 to 2003 are calculated. Considering the sand excavation, analyses show that the low water levels at Huiyang and Boluo, dominated by runoff, have been decreasing since 1980＇s, while the water levels at Fanwu, Shilong and Dasheng in the tidal reach have been increasing since 1990＇s. The huge sand excavation is the main reason for degradation of the low water level. The channel-fill volume is increased and river bed＇s level is decreased apparently after huge sand excavation. The strengthening of the tidal power caused by the significant topographic change is responsible for the rise of the low water levels in the tidal reach.