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The geographical environment of Zengcheng District

Zengcheng District is located in the east of Guangzhou City, Guangdong Province. Longdi, Honghuadi, Xinshanxi, Lizhiao, Zhongguling, and Danzhushan in the east are connected to Boluo County in Huizhou City; Sifang Mountain, Wokeshi, Longtanpu, Tiexianguan, Niuguzhang, and Zhengding are adjacent to Longmen County of Huizhou City; Dajianshan, Fenghuang Mountain, Dagushan, and Zhangguaoding in the northwest are adjacent to Conghua District of Guangzhou City; The western province's Sinopharm Farm, Shankou, Guanshan and Shacun are bordered by Huangpu District of Guangzhou City; the southern part faces Dongguan City across the river along the Dongjiang River. Licheng City is about 60 kilometers from the center of Guangzhou to the west, 60 kilometers from Boluo County to the east, 108 kilometers from Longmen County to the north, 51 kilometers from Conghua City to the northwest, and 40 kilometers from Dongguan City to the south. Since ancient times, Zengcheng has been the main thoroughfare from Guangzhou to other places in eastern Guangdong and a strategic military location for the defense of Guangzhou.

The geographical coordinates are 23°5? north latitude to 23°37? north latitude; 113°32? east longitude to 114°0? east longitude, with a total area of ​​1616.47 square kilometers. The geomorphological characteristics of Zengcheng: the terrain is higher in the north and lower in the south. The mountains are mainly low mountains, accounting for 8.3% of the area of ​​Zengcheng District. They are an extension of the Jiulian Mountains. The mountains run northeast and south-west, with middle and low mountains arranged equally. , during which the Dongjiang River and Zengjiang River were formed. Hilly land is mainly distributed in the central and southern parts, accounting for 35.1% of Zengcheng District's area. Most of the terraces are in the central and southern parts, accounting for 23.2% of Zengcheng District’s area. In the south is the delta plain, which together with the valley plain accounts for 35.4% of the area of ​​Zengcheng District.

Middle and low mountains: mainly distributed in Dajianshan, Niuguzhang, etc. in the north (height 500-1000 meters). It is composed of rocks such as sand shale and medium-fine-grained granite. The ridges are narrow and undulating, the slopes are steep, generally 40° to 50°, and the valleys are deeply cut, often forming waterfalls and canyons.

Hills: The absolute height is less than 500 meters, and the relative height generally does not exceed 200 meters. The shape is gentle, cut and broken, and the distribution is messy. Places such as the west of Xiaolou, the north of Zhengguo, and the west of Yonghe are mainly composed of granite. Generally, the slopes are gentle, the top of the mountain is round, and the water system is branch-shaped, with strong cutting.

Gently sloped hilly land: composed of granite and metamorphic rock. The height is mostly 200 to 400 meters, the top of the mountain is round, the slope is 20° to 30°, the water system is dendritic, and most of them form gentle slope valleys. Such as the southeastern part of the territory, the western part of Ningxi and other places.

Mesa: A broad platform surrounded by steep slopes is called a mesa. The height is less than 150 meters, the slope is around 25°, and there is no protruding mountain top, such as a platform composed of granite and metamorphic rocks. The Carboniferous limestone that appears sporadically in the Gaotan area often forms karst landforms such as karst residual hills, isolated peaks, and peak forests next to river valleys. Most of the surface layer has weathered into red soil and is overgrown with vegetation. Water storage conditions are poor and rainwater is often lost. The spring water has little exposure and dries up in the dry season.

The second terrace on the floodplain: distributed in the middle and upper reaches of Paitan River, 6 to 13 meters above the river surface, about 200 to 800 meters wide, and tilted toward the river bed at 2° to 4°. It is composed of modern alluvial deposits from the Quaternary Period and is 13 meters thick. The terraces are flat and the soil is thick. It is an area with good agricultural production.

The first terrace on the floodplain: distributed in the middle reaches of Zengjiang River, covering an area of ​​63 square kilometers. The terraces are 3 to 4 kilometers wide, 3.5 to 12 meters thick, and 1 to 6 meters above the river surface. The terrain from Zhengguo to Xiaolou is flat, with only one terrace, which is asymmetrical and 0.5 to 1.5 kilometers wide.

River valley plain: distributed in the area from Gaotan Dongdong, Lingshan to Paitan, covering an area of ​​41 square kilometers. The characteristics of the valley plains in Zhengguo and Xiaolou are: flat terrain, elevation 6 to 20 meters, curved rivers and many tributaries. There are low hills composed of granite and migmatite in the plain, which covers an area of ​​about 76 square kilometers.

River and sea accumulation areas: Xintang ~ Xiancun ~ Shitan ~ Sanjiang Delta plain is the northeastern plain of the Pearl River Delta. It was formed by the alluvial and accumulation effects of Dongjiang River and Zengjiang River and ancient bay sediments. It is 20 to 30 meters thick, with a maximum thickness of 39.6 meters. The Zengcheng water system belongs to the Dongjiang River system, a tributary of the Pearl River. There are three rivers with a drainage area of ​​more than 500 square kilometers, including the Dongjiang River, Zengjiang River and Xifu River, and six rivers with a drainage area of ​​more than 100 square kilometers. The average annual runoff in Zengcheng District is more than 1.9 billion cubic meters. There is also tidal water entering from the south, so water resources are abundant.

The Dongjiang River originates in Xunwu County, Jiangxi Province, flows through Longchuan, Heyuan, Huiyang, Boluo and other counties and cities to the south of Zengcheng, and is the boundary river between Zengcheng and Dongguan. Starting from the junction with Boluo in the southeast of the city and ending with the junction with Huangpu District of Guangzhou City in the southwest, the route is 30 kilometers, all in an alluvial plain area, with a river bed slope of 0.08‰, a criss-crossing river network, and many tributaries. Then it flows southwest into the Shiziyang River at the mouth of the Pearl River. It is a rare river in China that flows from east to west. The river section within the territory is 400 to 500 meters wide, with a maximum width of 800 meters. The water is deep and the slope is gentle, and 300-ton ships can be navigable. Below Xintang, 1,000-ton ships can be navigable.

Zengjiang is the most important river in the territory. It originally flowed directly into the Pearl River Estuary. After the formation of the Pearl River Delta Plain, it became a tributary of the Dongjiang River. Zengjiang River originates from Qixingling in Xinfeng County, flows through the northeast of Conghua County, turns to the northwest of Longmen County, and then turns south, becoming the boundary river between Zengcheng and Longmen. After the Modaokeng River flows from the northeastern corner of Zhengguo to Longtanpu and receives the Yonghan River, the flow rate increases. It passes through Zhengguo, Licheng and Shitan, and merges into the Dongjiang River at Guanhaikou. The total length is 203 kilometers and the drainage area is 3160 square kilometers. The average annual runoff is 3.59 billion cubic meters, with an average slope drop of 0.74‰.

Zengjiang is 66 kilometers long in Zengcheng, 90 to 220 meters wide, with a drainage area of ​​971 square kilometers, accounting for 60% of the Zengcheng District area, and a slope gradient of 0.17‰.

Paitan River originates from Makengzhang, Nankun Mountain, and is composed of five small rivers: Gaotan River, Lingshan River, Gaopu River, Chedong River and Xiaoxiao River. It flows through Paitanwei and joins Erlong River in Xiaolou Town and flows into Zengjiang River. The river is 36 kilometers long and has a slope gradient of 5.5‰. The basin area is 357.5 square kilometers, with an annual runoff of 500 million cubic meters.

Erlong River, formerly known as Chengxi River, originates from Yaji Mountain in Xiaolou Town. It flows through Erlongwei and Labu Village, and merges into Zengjiang River in Dalou Village. The river is 22.5 kilometers long and has a slope gradient of 2.8‰. The basin area is 122.7 square kilometers, and the annual runoff is 150 million cubic meters.

Pingping water, also known as Jiuqu water, originates from Zhengguo Maji Ridge and flows into Zengjiang River through Baihu Lake and Lengshuikeng Water. The river is 18.7 kilometers long and the drainage area is 48 square kilometers.

Xifu River, formerly known as Suifu River, is the largest river in the western region of the country. It originates from Dayegu Mountain, flows through Fuhe and Xiancun, and joins the Dongjiang River in Xiangtou Village. The river is 58 kilometers long and has a gradient of 1.6‰. The basin area is 580 square kilometers, and Zengcheng area is 457.7 square kilometers. The average annual runoff is 510 million cubic meters. In the early 1950s, navigation was possible below Fuhe. After the late 1950s, the riverbed became shallow due to soil erosion, and gates were built along the river. Only a few kilometers south of the railway were navigable. Zengcheng District has a south subtropical oceanic monsoon climate, with the Tropic of Cancer passing through the north of Zengcheng. It is characterized by high temperatures, abundant rainfall, few frost days, and sufficient sunlight. Crops can be cultivated all year round. However, the climate is changeable due to the different timing and strength of monsoons. Affected by the terrain, the climate in the northern mountainous areas is different from that in the southern plains.

Climate characteristics throughout the year: In spring, from the beginning of spring, there are continuous rains, humid air, and low temperatures, generally between 12.7 and 21.7°C. In summer, starting from mid-April, the temperature rises, with the highest temperature being 28.5°C. The weather is often controlled by subtropical high pressure, and the air is sultry; there are many frontal rains from April to June, and many typhoons and rains from July to September; floods often occur. In autumn, starting from late October, affected by the dry and cold air from the north moving south, the temperature drops, drought and little rain occur, but the weather is cool; from December to January, there are often cold waves and occasional frost days. In winter, there is no climatological winter in the territory, but people still call November to January when the temperature is lower.

The multi-year average air pressure is 1012.2 millibars, with a large difference between winter and summer. In winter, controlled by the polar high pressure, the air pressure is high, with an average of about 1020 mbar from December to January; in summer, affected by tropical cyclones, the air pressure is low, with an average of about 1003 mbar from July to August.

According to statistics from 1994 to 2005, the annual average temperature is 22.2℃ (the historical value is 21.8℃), with a maximum inter-annual difference of 1.5℃. The average temperature in July is 28.3℃. The highest temperature occurred on July 2, 2004 and July 18, 2005. The extreme maximum temperature was 38.6℃. The longest number of consecutive high temperature days was 9 days (high temperature definition: temperature ≥35.0℃), which occurred from July 13 to 21, 2005. The average temperature in January is 13.6℃, ​​and the extreme minimum temperature is 0℃ (in 1999).