Research On The Evolution Of River System In The Three North Plains (1387-1987

This paper focuses on the evolution mechanism of the river-pool system in the Sanbei Plain since the Ming Dynasty,and discusses the construction and livelihood changes of the water network in the silt-rising plain,taking the sea ponds,lakes,weirs,the Yuyao River,the coastal water network,and the tidal ditches in the salt area as the objects of study.The first chapter compares the administrative changes of Yuyao,Cixi,and Zhenhai counties(cities and districts)and analyzes the shaping role of the remaining veins of the Cuiping hills embedded in them on the water system of the Sanbei Plain.From the perspective of the Hepu system,the area of the Sanbei Plain should not be limited to the coastal plain north of Dagutang,but also includes the Yuyao River and its tributaries.The second chapter rakes the evolution of the hydrogeomorphology of the area south of Dagutang in the Sanbei Plain before the 14 th century from a long time perspective.The storage of light water in the lakes extended the scope of agricultural development,allowing people to leave the shores of the Yuyao River and cultivate coastal lands.Second,the installation of the weir gate allowed the lake’s storage to further cover all the plain land south of Dagutang.In the actual maintenance and operation of the water conservancy system,there were often disputes and conflicts due to the differences in status between different regions under the same flood and drought.Through constant negotiation and abolition,people shaped the pattern of the water system south of Dagutang.Chapter 3 restores and analyzes the use of tides-the Yuyao River tide and Hangzhou Bay tide-by the river and river system during the Ming and Qing dynasties.From the 14 th to the mid-18 th centuries,the coastline was slightly pushed northward in the midst of fluctuation,which led to the initial exploration of mutual irrigation by drawing tides from the north and south of Dagutang,outlining a simple "comb-like" water system pattern in the coastal sandy area,roughly following the sequence of pond construction-river opening-lock installation.-The sequence of opening the river and setting up the gate evolved towards the sea.The use of tidal water made the river and river system face the threat of tidal invasion and siltation at the same time,and the river and river system in the Sanbei Plain grew in the game of compromise between the various forces.Chapter 4 analyzes data related to economic and water resources from the Republic of China survey report,and examines the water resources conditions in the coastal saltlands and the cotton and grain areas south of Qitang.As far as salt production is concerned,this paper argues that the desalination of brine quality is an important reason for the decline of the saltlands.The quality of brine does not depend on the salinity of seawater,but on the adsorption of salt by the soil,the tidal capacity of the tidal ditch and the smoothness of drainage.In terms of water conservation in the cotton and grain area,the horizontal river and longitudinal pu that have been excavated and extended over the ages have laid the foundation for drainage and irrigation in the coastal sands.This water system structure is not effective in regulating droughts and floods,and cannot guarantee the yield of cotton and rice.The narrow Yuyao River is also unable to meet the drainage needs of the newly silted land.The river-pool system includes the Yuyao River,coastal lakes,weirs and gates,and tidal ditches for the salt industry,and these geographical elements were finally formed through a long period of hydraulic exploration.The river-pool system of the Sanbei Plain is the optimal solution to the problem of coastal plain development in the historical period.