近年珠江三角洲洪季余水位和潮差的演变特征研究

Research on the Evolution of Residual Water Level and Tidal Range of Flood Season in the Pearl River Delta in Recent Years

珠江三角洲径潮动力受高强度人类活动的干扰,发生了与自然演变截然不同的变化。为探明近年来珠江三角洲河网内径流与潮汐动力特征的演变,基于珠江三角洲“997”和“177”两场洪水的逐时水位流量资料,采用傅里叶变换方法,获取水位时间序列中的余水位(低频)和潮汐(高频)成分进行对比分析。结果表明:马口、三水断面余水位-流量关系曲线下移,同流量下余水位明显降低,而三角洲下游口门附近余水位略有抬升,使得河道沿程余水位比降变缓,河网内水深增大导致潮汐向上游传播的阻力变小,潮差衰减率也相应减小。近年来三角洲上游水库建设和河网内大范围的航道整治工程导致的河网河道地形下切是径潮动力发生上述变化的主要原因。

The river and tidal dynamics in the Pearl River Delta(PRD)are disturbed by strong human activities and changes different from the natural evolution.To explore the evolution of river and tidal dynamic characteristics in the river network of the PRD in recent years,based on the hourly water level and discharge data of two floods in the PRD,“99.7”and“17.7”,this paper adopts the Fourier transform method to obtain the residual water level(low frequency)and tidal(high frequency)components in the water level time series for comparative analysis.The results show that the relation curves of residual water level and discharge at Makou and Sanshui stations move down,with lower residual water level at the same discharge;whereas the residual water levels near the lower mouth of the PRD rise slightly,making the decrease in the residual water level slope;the increase in water depth results in the decrease in the resistance of tidal propagation,which leads to the attenuation rate of tidal range also decreases accordingly.The riverbed down-cutting caused by reservoir construction and waterway regulation is the main reason for the change of river and tidal dynamics of the PRD in recent years.