珠江磨刀门河口水位与海平面、上游流量的联合分布关系异变研究

ABRUPT VARIATION OF JOINT DISTIBUTION OF WATER LEVEL,SEA LEVEL,AND RIVER DISCHARGE IN THE MODAOMEN ESTUARY OF THE ZHUJIANG(PEARL)RIVER

河口的水位变化是径潮动力相互作用的结果,但近30年来,强人类活动对河口环境的影响已远超环境自我修复能力,导致水位发生异变。为研究这种变化,本文选取人类活动影响剧烈的珠江磨刀门河口作为研究区域,采用Copula方法定量分析在同一上下边界(上游流量和口外海平面)下由强人类活动引起的水位异变。结果表明:1)强人类活动后,河道地形下切显著,外海海平面对沿程各站水位的线性影响增强,上游马口流量对水位的线性影响减弱。2)强人类活动后甘竹至灯笼山站同概率水位事件明显降低;三灶海平面呈上升趋势;马口流量分布特性变化不明显。3)水位与海平面、流量的联合依赖关系发生明显改变,低水位与海平面关系的敏感度增加,而高水位与海平面关系的敏感度下降。低水位与流量关系的敏感度基本不变,而高水位与珠江流量关系的敏感度明显下降。4)强人类活动后各站水位变化幅度变窄,在相同概率海平面及流量驱动下,强人类活动后各站水位均有明显下降,水位与海平面、流量遭遇概率为0.1—0.9时,其月均水位下降幅度达0.01—1.24m。低海平面和低流量联合驱动下各站水位的下降幅度明显小于高海平面和高流量联合驱动下月均水位的变幅,而且上游站位的水位下降幅度明显大于下游站位。本研究成果可为强人类活动的影响辨识及珠三角水资源的合理配置和可持续发展利用等提供技术支撑。

The change of water level in an estuary is resulted from dynamic interaction of the runoff and tide.However,in the past 30 years,the influence of strong human activities on the estuary environment has far exceeded the self-healing ability of the environment,resulting in the abnormal change of water level.To study such changes,the Modaomen estuary of the Zhujiang(Pearl)River was selected as a typical area of study.The Modaomen estuary was dramatically affected by the intensive human interventions.The Copula method was used to quantitatively analyze the variation of water level caused by strong human activities at the same upper and lower boundary(the river discharge at Makou hydrological station and sea level outside the estuary).The results show that after intensive human interventions,river-bed was substantially deepened.The impact of sea level on the monthly averaged water level observed at each station was considerably enhanced,while the impact of river discharge observed at Makou station on the monthly averaged water level at other stations was weakened.The water level that obtained at Ganzhu and Denglongshan stations after intensive human interventions showed a lower water level under the same probability event.The sea level of Sanzao station showed an increasing trend after intensive human interventions.The change of probability distribution of river discharge observed at Makou station displayed no apparent change after intensive human interventions.The joint dependencies of water level,sea level,and river discharge presented an obvious change.The sensitivity of the relationship between low water level and sea level increased,while the sensitivity of the relationship between high water level and sea level decreased.The sensitivity of the relationship between low water level and river discharge remained unchanged,while the sensitivity of the relationship between high water level and river discharge of the Zhujiang River decreased significantly.After the intensive human interventions,the water level distribution in each station was narrowed.At a same given probability of sea level and river discharge,the water levels show an ever-decreasing trend in each station.When the encounter probability of water level-sea level and water level-river discharge ranging 0.1-0.9,the monthly averaged water levels decreased by 0.01-1.24m.The variation under the condition of low sea level and low discharge was significantly lower than those for high sea level and high discharge.In addition,the monthly averaged water levels observed at upstream stations decreased more significantly than those of downstream stations.Results obtained from this study can provide technical support for the assessment of the impact of intensive human interventions and the sustainable development and utilization of water resources in the Zhujiang River deltaic regions.