珠江河口界面特征与河口管理理念

河口是河流系统与海洋系统之间的界面,它首先是河流与海洋之间的物质界面。河流水体与海洋水体间最大的物质差异是盐分,因此,采用盐度作为河口界面的界定标准,将河口界面界定为盐度为0.5~30的由冲淡水控制的河口中心区域。在此基础上应用界面理论,分析了河口的渗透性和防御性及其动力、沉积、生物与地貌响应。借鉴Gilbert三角洲的动力分类方法,将河口界面按动力结构分为径流优势型、潮汐优势型、波浪优势型及其过渡类型。每一种河口界面又可细分为动力、沉积、地貌及生态等次一级界面。在珠江三角洲地区,磨刀门、蕉门河口等径流优势型河口界面主要承担泄洪任务,而虎门、崖门等潮汐优势型河口界面在纳潮能力上更有优势,其间通过河道支汊相互沟通和联系,形成了珠江河口界面的多层次结构。河口界面动力的复杂性,构成了河口界面形态和功能的复杂性。这些功能包括开发利用功能、生态功能、防洪功能和社会服务功能。河口管理的最高目标是河口的永续健康、结构和功能彼此协调,保持河口界面结构和功能的完整性。河口界面的复杂性对河口管理提出了更高的要求,要注重河口管理内容的综合性、问题的复杂性和管理效应的长周期性。针对珠江河口生境退化、海岸侵蚀、污染严重、咸潮活动加剧和口门淤积造成排水不畅等诸多问题,以及河口无序开发利用、管理体制混乱、公众参与少的管理现状,结合珠江河口界面整体、动态、彼此联系的特点,提出珠江河口管理"科学、和谐、安全和预警"的管理理念,由行政管理转变为服务管理,切实做好珠江河口管理工作。

Estuary boundary characteristics of the Pearl River Estuary and their effects on the management idea

Interface theory is a pioneer theory setup by Cao(1987) to study the general laws of systematic boundary.Interface refers to as systematic boundary which has many special characteristics,such as penetrability, resistibility,and self-adaptability etc.Estuary is the interface between fluvial system and marine system,which is defined as Estuary Boundary(abbre EB) and it is a material interface first.The supreme difference between fluvial water and sea water is salinity which is used as the standard to define EB,a central area of the estuary controlled by the fluvial diluted water with salinity of 0.5~30.The adaptability of EB and its effect on sedimentation,biology and morphology are discussed.EB is an energy dissipative environment because of the interaction of multiple dynamics such as runoff,tide,wave and wind which results in differential sedimentation of the silt load: coarser silts(bed sediment) settle down before entering EBs,less coarser silts in the EBs and fine silts scatter into the continental shelf.Estuarine biology presents obvious boundary characteristics in the mixed water environment and the biodiversity in EBs is lower than in fluvial system and ocean system.Based on the delta dynamic classification of Gilbert(1914),Pearl River EBs are classified as runoff dominant,tide dominant,wave dominant and their transition classes,each class can be subdivided into dynamic,sediment,morphology and biology sub-boundaries.Runoff dominant EBs(Modaomen,Jiaomen etc) in Pearl River delta area have more capability on flood drainage,while tidal dominant EBs (Humen,Yamen) are more powerful to accommodating tide water.They are linked each other by many branches forming multilevel structure of the EBs.Because of the water level difference between the West and North river trunk channels and the two tidal reaches,the trunk channel is bursted,forming branches,of which the development takes effect of balance of the whole EB of the Pearl River.The complexity of the EB's dynamics results in its structural and functional diversity including exploitation function,ecological function,flood control function and social service function.The base of estuary management is to understand complex adaptive nature of estuary systems,and the supreme goal of estuary management is to achieve the harmonization of EB structure and function and sustainable health of EB,meanwhile maintain the integrity of EB structure and function.Special attention should be put on the comprehensive and complex nature of management and periodicity of the management effect.In the light of increasing risks such as habitat degradation,severe pollution,coastal erosion,intensifying salt-water intrusion and blocked drainage resulted from outlet siltation in the Pearl River estuary and problems in estuary management such as out-of-order exploitation,chaos of regulation system and the lack of public participation,combined with the integral,dynamical and interrelated characteristics of Pearl River EB,a scientific,harmonious,safe and foreseeing idea of estuarine boundary management is raised to direct the estuary management.