Geographical environment of Doumen District

The landform types in Doumen District of Zhuhai City include low mountains, hills, terraces, vast sedimentary plains and beaches that are still developing. Therefore, it presents an obvious layered landform of one flat, one convex, one flat and one concave. The topography of the whole area is characterized by low mountains, vast plains, numerous isolated mountains, criss-crossing waterways, dense rivers, rapid siltation and beach exposure. The northeast of the territory is lower than the southwest, and the alluvial zone on the edge of the hill is higher than the sedimentary plain on both sides of the river.

The hills in the Pearl River Estuary and the alluvial plain form Doumen landform, and the small islands separated by river network on the alluvial plain are the main residence of the water people. It is said that a long time ago, Doumen was a bay, and the peaks in the bay stood tall, and the Boxwood Mountain in the middle spread out like a huge black dragon. Xijiang water here, divided into five tributaries. They took root here with the fertile soil along the Xijiang River, and continuously deposited into more than 20 oasis plains with vertical and horizontal river networks.

Xijiang River is the longest river in southern China and the third largest river in China, second only to the Yangtze River and the Yellow River. The traffic volume ranks second in the country, second only to the Yangtze River. Originated in Yunnan, it flows through Guangxi and joins Dongjiang and Beijiang rivers in Sanshui, Foshan, Guangdong. Its mainstream flows into the South China Sea in Jiangmen and Zhongshan. It is called the Pearl River together with Dongjiang River and Beijiang River.

Modaomen, located in Qirenshi, Hongwan, Zhuhai, is the main outlet of Xijiang River runoff. Modaomen's annual runoff is 92.3 billion cubic meters, accounting for 28.3% of the total runoff from the Pearl River into the sea, and the annual sediment transport is 2310.4 million t, accounting for 33% of the total sediment transport from the Pearl River into the sea. The maximum tidal range of the sharpening gate is 1.9m, and the maximum tidal range is 2.29m.

Jitemen is located in Dalin, Doumen District, adjacent to the west side of the sea area in Modaomen, and is the estuary of Jitemen waterway. The annual runoff of Jiti Gate is 65.438+097 billion cubic meters, accounting for 66.5438+0% of the total runoff of the Pearl River into the sea, and the annual sediment transport is 4.96 million t, accounting for 7% of the total sediment transport of the Pearl River into the sea. The maximum tidal range is 2.44m, and the maximum tidal range is 2.71m. Jiti Gate is a sea outlet formed after the completion of 1959 Niwan Gate Sea-blocking Project. Prior to this, Niwan Gate was located at the upstream of Jiti Gate 16km, and it was one of the eight major seaports in the Pearl River.

Tiger Jumping Gate is the exit of Tiger Jumping Gate Waterway. The annual runoff of Hutiaomen is 20.2 billion cubic meters, accounting for 6.2% of the total runoff of the Pearl River into the sea, and the annual sediment transport is 5.09 million t, accounting for 7.2% of the total sediment transport of the Pearl River into the sea. The maximum tidal range is 2.5 1m and the maximum tidal range is 2.66m m.

Local water resources: the rainfall in Doumen District is1/kloc-0 ~ 3339 mm, the average rainfall for many years is 1998.8 mm, the average runoff depth for many years is 120 1 mm, and the annual runoff is 930 million cubic meters. The average annual runoff coefficient is 0.50. The land area of Doumen District is 1 1 square kilometer, the average runoff depth for many years is 82 1 mm, and the total amount of shallow groundwater is about 50 million cubic meters.

Passenger water resources: 76.9 billion cubic meters of transit passenger water. Among them, Modaomen Waterway is 52.3 billion cubic meters, Jitemen Waterway is 65.438+04 billion cubic meters, and Hutiaomen Waterway is 65.438+006 billion cubic meters. Look at the water consumption of the main guests: the average annual fresh water resources in the region are about 77.88 billion cubic meters, and the per capita water consumption is 266,500 cubic meters.

Doumen District is located in the Pearl River Estuary, and five of the eight gates in the Pearl River Estuary (Yamen, Modaomen, Jiti Gate, Niwan Gate and Hutiao Gate) pass through Doumen. Rivers in the area crisscross, and the larger river is Huangyang River. Luozhou River, Friendship River, Shengda River, etc. There are countless rivers, and many rivers divide Doumen into small islands, making Doumen District a famous water town in the Pearl River Delta. Doumen District, located in the south of the Tropic of Cancer, is rich in heat all year round, with abundant sunshine, long summer and short winter. ciel phantomhive is extremely hot, less cold in winter, with high humidity, abundant clouds, abundant rainfall, rainy and hot seasons and distinct wet and dry seasons. Typhoon and rainstorm are frequent, and low temperature and cold occur from time to time, which belongs to the humid climate of south subtropical monsoon.

Features of the first and fourth seasons

(1) Spring

The climate in spring is characterized by less sunshine, high humidity, more rain and fog, and the weather is getting warmer. In early spring, cold air invaded south, and it is common to have "cold spring" weather with low temperature and rainy weather. In the first ten days of April, the warm and humid airflow developed, the cold air slowed down and stopped, and the warm and humid southwest wind strengthened, forming a low-level jet stream, which was easy to produce heavy rain and heavy rain, and the rainfall increased, entering the pre-flood season. In the middle and late May, the southwest monsoon of the South China Sea formed, with frequent rainfall, and entered the peak of the pre-flood season, which lasted until the early summer. 199 1, 1993, 1994, 1995, 1999 had less rain and spring drought.

(2) Summer

In midsummer, the southeast wind or southerly wind blows, and the weather is sunny, hot and sunny. The sunshine hours are the most in the whole year, and the highest temperature is about 35℃. There are many tropical depressions and typhoons in the South China Sea and the Western Pacific, and August and September are frequent periods, which not only bring abundant rainfall, but also often cause disasters due to typhoons and rainstorms.

(3) Autumn

From the late September of 10 to the early October of 10, westerly jet moved southward seasonally, and the lower summer monsoon retreated southward, and the northeast monsoon began to form, making the whole area crisp in autumn. In early autumn, sometimes it is still affected by tropical depression and typhoons in the South China Sea and the western Pacific Ocean, bringing rain. Later, as the typhoon moved southward, the impact decreased. 1 1 month later, the cold air began to strengthen, the temperature gradually decreased, and the dry season began.

(4) Winter

The northeast monsoon is blowing in the county town, and the cold air often goes south. Sometimes the temperature drops suddenly, accompanied by strong winds of magnitude 6 or above, lasting for many days. Subsequently, as the cold air moves southward to the ocean and air mass, the temperature gradually rises. This quasi-periodic repeating process of seasonal trend in Northeast China is the basic feature of winter climate. At the end of winter, the warm air in the South China Sea is gradually strengthened, which is easy to cause cold and warm airflow confrontation, and often leads to low temperature and rainy weather or long-term rainy weather. It is characterized by dry and cold in the first winter and wet and cold in the second winter.