- Geographical Position
Zhenhai is located in the subtropical monsoon climate zone, which is mild and humid, with four distinct seasons, sufficient sunshine, abundant rainfall and long frost-free period. The annual average temperature is 16.3 ℃, and the lowest daily average temperature remains stable above 10 ℃, lasting for 231 to 235 days. The annual effective average accumulated temperature ranges from 4,920 ℃ to 5,030 ℃. The frost-free period is 237 days; the annual precipitation is about 1,310 to 1,370 millimeters; there are 148 rainy days. The annual sunshine duration is 1,944.3 hours, and the sunshine rate is 44%. The typhoons in summer and autumn, low temperatures and rainy weather in spring, and cloudy and rainy weather in autumn are natural factors of agricultural instability.
[Soil and Vegetation] The soil in the entire district is divided into three zonal soil groups, namely low mountains and hills, coastal plains, and plains with networks of rivers, with a total soil area of 1.086 million mu. Low mountains and hills, including mountain dry land, mountain ridge land, and hillside land of 539,000 mu in total, accounting for 49.7% of the county's soil area; the coastal plains start from the Guantang Road in the north of the river, and end at the Shigaotang and the Wanggongtang in the south, forming two crescent shaped marine sedimentary plains in the north and south, covering an area of 316,000 mu, accounting for 29.1% of the county's soil area; the plains with networks of rivers, located between the low mountain plains and the coastal plains, cover an area of 231,000 mu, accounting for 21.2% of the county's soil area. Vegetation. It is in the middle subtropical evergreen broad-leaved forest subregion and the forest zone with Castanopsis eyrei and Schima superba of the Zhejiang-Fujian Hill Area. In history, forests had been repeatedly destroyed, and primitive vegetation almost disappeared and replaced by secondary vegetation and artificially introduced vegetation such as coniferous forests, broad-leaved forests, shrubs, grasslands, and so on.
The total length of herbaceous vegetation in the coastal mudflat is about 89.7 kilometers. Phragmites communis grow along both banks of the mudflat dyke. There are also Scirpus triqueter, Suaeda salsa and Erigeron pellicornis in the mudflat below the dyke. The coverage rate of herbaceous vegetation is 40% to 70%. The coastal hilly coniferous forest accounts for 90% of the forest land of 309,200 mu in the county. The warm coniferous forest mainly includes Pinus massoniana, black pine and fir, of which Pinus massoniana accounts for 190,000 mu; the temperate coniferous forest is mainly composed of Cryptomeria fortunei, Pinus ussuriensis, and so on, with only a small distribution. The existing coastal hilly broad-leaved forest is mostly of secondary type, and is mainly composed of Lithocarpus chinensis, Cyclobalanopsis glauca, Castanopsis sclerophylla, Liquidambar formosana, Schima superba, Sclerotinia glauca, Photinia rubra, etc., which are mostly distributed in the county's forest farm, the Gonghe, the Yang'ao and the Zhaobao Mountain. The bamboo forest vegetation in the coastal plain often includes camphor, Schima superba, fir, and phyllostachys pubescens. Among them, the coastal phyllostachys vivax is a specialty of Zhenhai, with an annual area of about 400 mu.
[Rivers, Seas and Mudflat] The Yongjiang River, originating from Fenghua and the Wushan Mountain in Xinchang, flows to the northeast, passing through Hengzhang and arriving at the Sanjiangkou in Ningbo; the other stream flows from the Xiliang Lake Dam in Shangyu, passes through Yuyao and arrives at the Sanjiangkou in Ningbo, and then flows to the Zhenhaikou in the northeast, entering the Huibieyang Sea. The drainage area is 5,299 square kilometers. The area below the Sanjiangkou is called the Yongjiang River, which used to be called as the Dajia River in ancient times, with a flowing length of 26 kilometers, 16 out of which is located in Zhenhai. The Yongjiang River is a perennial river in the plain, with a current port road width of 270 to 404 meters and 600 meters at the maximum. The estuarine tides are irregular semi-diurnal tides, with an average tidal range of 1.75 meters; the average rising tide lasts for 6 hours and 23 minutes, while the average falling tide lasts for 6 hours. There are 24 foggy days every year.
The Huibieyang Sea, located to the northeast of the Zhenhai District, is approximately 40 kilometers long from north to south and 30 kilometers wide from east to west, covering an area of approximately 1,200 square kilometers. It is adjacent to the Zhenhai District, the Cixi City, and the Zhoushan Area. The depth of water in the sea is mostly between 5-10 meters, gradually deepening from west to east; the annual average water temperature is 17.3 ℃, the annual average salinity 18 ‰, the annual average wind speed 5.7 meters, and the annual average foggy day 12.7 days. Tides are irregular semi-diurnal tides. The annual average drop is about 2 meters. The bottom material is all sediment. Ships with a capacity of less than 50,000 tons are able to travel.
Mudflat in the north of Zhenhai. The northeast coast of the Zhenhai District starts from the Youshan Hill outside of the Zhenhai Port Area in the east, ends at the Bazi Hill in Xiepu in the northwest, and borders the Huibieyang Sea., with a total length of 16.5 kilometers from east to west, 1.5 kilometers wide from north to south, covering an area of 20.8 square kilometers. It is composed of silt and silty sand and mud and has a long duration of falling tide and thick mud, rich in mud snail, yellow clam, jumping fish and so on; due to its advantageous geographical location, it has become an industrial development base with an enclosed area of 25,000 mu, serving as industrial land for the Zhenhai Refining and Chemical Company, the Zhenhai Port Area, and the development zone in the north of the Zhenhai District.
[Water Resources] The average annual total water resources in the entire district is 528.89 million cubic meters (including reused water), of which surface water resources is 487.59 million cubic meters, accounting for 92.2% of the total; groundwater resources is 41.3072 million cubic meters, accounting for 7.8% of the total; the water consumption per capita is 1,100 cubic meters, and the water consumption per mu is 1,230 cubic meters. The average annual precipitation in the entire district is 1.1009 billion cubic meters; the average annual runoff depth is 470 to 920 millimeters; the total amount of runoff is 509 million cubic meters. The spatiotemporal distribution pattern is similar to precipitation.
[Tide] The tide at the Yongjiang Estuary is of an irregular semi-diurnal type, with a cycle of 24 hours and 50 minutes, with 6 hours in between of the rising tide and falling tide. However, due to weather changes and other factors, the error in the rising tide time is about 1 hour; Zhenhai has a maximum tidal range of 1.9 meters and an average tidal range of 1.75 meters; the average rising tide velocity on the surface is 69 cm/s, and the average falling tide velocity is 58 cm/s.
There are three types of waves near Zhenhai, namely wind waves, swell waves, and mixed waves, but with mixed waves are the main type. The average wave height on the sea surface is 0.5 to 0.8 meters, with a maximum wave height of about 1 meter and a period of 3.0 to 4.0 seconds. Most of the waves tend to lean towards the east. In winter, the sea surface often experiences northerly winds of magnitude 8 to10, resulting in northerly waves with an average wave height of 0.5 to 2.5 meters and a maximum wave height of 1.0 to 3.0 meters, with a period of 4.5 to 6.0 seconds.
[Animal Resources] There are 29 species of mammals. According to the "Zhenhai County Annals" of the Republic of China, during the Ming and Qing dynasties, tiger infestations often occurred in the region south of the Yangtze River, causing daytime casulties; ferocious tigers used to come to Zhenhai for many times. In 1941, a tiger was captured in Tiaoao, Guoju, and none has been found after the liberation of the country. The number of other mammals is decreasing, but in recent years, the number of wild boars have increased. There are 42 common bird species, including eagles, magpies, crows, and myna. From the beginning of the Anti-Japanese War to the early days of liberation, due to the serious felling of big pine forests, camphor trees and ancient cypress trees, the number of mammals and birds lost their nesting sites and declined sharply. In recent years, with the continuous improvement of the environment, migratory birds can be seen in many places in Zhenhai, especially in the Ningbo University and the Zhenhai Refining and Chemical Company. Every March, thousands of egrets of different kinds are attracted to settle and lay eggs, and then fly south at the end of October. The amphibian "Zhenhai Acanthostega", which are born along the stream of a forest farm of the Ruiyan Temple, is now listed as protected animals in the Zhejiang Province. Its body is 7 to 8cm long with waxy black back and sides and a vermilion belly dotted with irregular black spots. Its head is large, limbs slender, and the tail flat.