Meteorological hydrology

Henan province is located in the transitional zone between warm temperate zone and subtropical climate, and the climate has obvious transitional characteristics. With the Qinling-Huaihe line as the boundary, Xinyang and Nanyang in the south belong to subtropical humid and semi-humid monsoon climate zones, while other cities in the north belong to warm temperate arid and semi-arid monsoon climate zones. Its climatic characteristics are generally cold and rainy in winter, dry and windy in spring, hot and rainy in summer and sunny and hot in autumn.

According to the data of Henan Meteorological Bureau, the annual total solar radiation in the whole province is 4600 ~ 5000 MJ/m2, which is smaller in the south of Huaihe River and mountainous areas. The annual actual sunshine hours are 2000 ~ 2600 h; The annual average temperature is 12.8 ~ 15.5℃. The highest temperature is in July, and the monthly average temperature is 27 ~ 28℃. The lowest temperature is 65438+ 10 month, and the monthly average temperature is -2 ~ 2℃. The frost-free period of the whole year is between 180 ~ 240 d, the utilization time of air conditioning in summer is from June to September, and the heating time in winter is generally from 1 15 in October to 15 in March of the following year, and the heating and cooling time is equivalent.

The precipitation in the whole province varies greatly from year to year and is unevenly distributed in time and space. The annual average precipitation in the whole province is about 600 ~ 1200mm, reaching 1000 ~ 1200mm in the south, 700~900mm between Huanghuai and only 600~700mm in the north and west. The annual average relative humidity in the whole province is mostly between 65% and 75%, and gradually decreases from southeast to northeast. Due to the influence of monsoon, severe weather phenomena such as drought, dry hot wind, strong wind, rainstorm and hail are more frequent. See table 2- 1 for the meteorological elements of each city.

Secondly, hydrology.

There are many rivers in Henan province, which branch radially from west to north and from east to south, belonging to Haihe River, Yellow River, Huaihe River and Yangtze River. There are more than 500 rivers1in the whole province, including 493 rivers with basin area above 1000km2, 60 rivers with basin area above 1000 km2, 7 rivers with basin area above 5000km2 and 9 rivers with basin area above 1000 km2. Among the 18 cities in this study, Luoyang, Sanmenxia and Jiyuan belong to the Yellow River Basin, Nanyang belongs to the Yangtze River Basin, Anyang, Xinxiang, Jiaozuo, Puyang and Hebi belong to the Haihe River Basin, and Zhengzhou, Kaifeng, Xuchang, Luohe, Zhoukou, Pingdingshan, Zhumadian, Xinyang and Shangqiu belong to the Huaihe River Basin.

Table 2- 1 List of Meteorological Elements of Major Cities in Henan Province

1. Yellow River system

The Yellow River is the largest river in Henan Province. It enters Henan from Tongguan, Shaanxi Province, crosses the north-central part of Henan Province, and leaves Shandong Province in Zhangzhuang, Taiqian County, with a length of about 7 1 1km.

To the west of Jin Meng, the main stream of the Yellow River, is a canyon with steep mountains and fast flowing water. Now there are two major water control projects, Sanmenxia and Xiaolangdi. From the golden dream to Taohuayu, the river bed gradient decreased, the water flow slowed down and the sediment began to deposit. The Yellow River enters the lower reaches of the Yellow River from Taohuayu, Zhengzhou, and its channel is strongly silted. Due to the high sediment concentration in the river course and siltation in the downstream, the riverbed of the Yellow River is 3 ~ 5m higher than the back river surface, and the maximum is over 10m, forming the surface watershed and the backbone of the Huanghuaihai Plain.

According to the data of Huayuankou Hydrological Station 1949 ~ 2000 (Figure 2- 1), the annual average flow of the Yellow River is1269m3/s; The maximum measured peak flow is 22,300m3/s (1 July 958 17), and the minimum flow is 0 (1June 9601). The average sediment concentration for many years is 26.4kg/m3, and the maximum annual average sediment concentration is 53.6kg/m3. The measured maximum sediment concentration is 546kg/m3( 1977).

The Yellow River system includes the Yellow River and its tributaries, I River, Luohe River, Qinhe River, Hongnongjian River, Hesui River, Jindi River and natural Yan Wen Canal, with a drainage area of 3.62× 104km2, accounting for about 2 1.7% of the total area of the province. Luo Yi flows through Luoyang and He Sui flows through Jiyuan. There are eight cities along the Yellow River: Sanmenxia, Luoyang, Jiyuan, Jiaozuo, Xinxiang, Zhengzhou, Kaifeng and Puyang.

Figure 2- 1 Multi-year average discharge curve of Huayuankou Hydrological Station of the Yellow River

2. Huaihe River System

The main rivers in Huaihe River Basin include the main stream of Huaihe River and its tributaries in Huainan, the rivers in Honghe, Heying and Yudong Plain. The average discharge of Huaihe River for many years 174m3/s (Huaibin Hydrological Station), with a drainage area of 8.83x104km2, accounting for 52.8% of the total area of the province. Huainan, the main stream and tributary of Huaihe River, originated from the northern foot of Dabie Mountain, accounting for 17.5% of the total area of Huaihe River basin in the province. The tributaries on the left bank mainly originate from the Funiu Mountain system in the west, the Yellow River in the north and northeast, and the abandoned south dike of the Yellow River. There are many secondary tributaries along the way, accounting for 82.5% of the total area of Huaihe River basin in the province. The tributaries on the left and right banks are asymmetrically distributed. The river source in hilly area is short and urgent, and it is easy to become a flood disaster after entering the plain.

The Huaihe River in Huainan and its tributaries originate from Taibai Peak of Tongbai Mountain in Tongbai County, and flow eastward to Chen Dong Village, sanhejian Township, Gushi County, and enter Anhui Province. The length of the river above the provincial boundary is 4 17km, and the water system of the main stream of Huaihe River includes the main stream of Huaihe River, Huainan tributaries and Huaibei tributaries above Honghekou, with a drainage area of 2 1730km2. The main tributaries of the south bank are: Shihe River, Zhugan River, Zhaihe River, Yellow River, Bailu River, Shihe River and Guanhe River. Among them, Shihe River flows through Xinyang City.

The Honghe River system originates from Longtou Mountain in Wugang City and flows into the Huaihe River at Honghekou in Huaibin County, with a total length of 326km, an annual average flow of 27.7m3/s (Bantai Hydrological Station) and a drainage area of 12325 km2. Ruhe River is its main tributary.

He Ying, located in the hinterland of Henan Province, is the largest tributary of the Huaihe River Basin. Shahe is the main road, and the section below Zhoukou to the provincial boundary is also commonly known as Shahe. He Ying originated at the southern foot of Songshan Mountain, flowed through Xuchang and Zhoukou, and entered Anhui at the border. The annual average discharge of He Ying is 106m3/s (Zhoukou Hydrological Station), the length of the river above the provincial boundary is 4 18km, and the drainage area is 34400km2. The main tributaries are Shahe, Fenquan River, Qingfei River, Jia Luhe River and Heizi River, among which Jia Luhe flows through Zhengzhou, Qingfei River passes through Xuchang, and Shahe flows through Luohe and Zhoukou.

East Henan Plain Water System The east Henan Plain water system mainly includes the Wohe River, Huiji River, Baohe River, Huihe River, Tuohe River and the old course of the Yellow River, among which Huiji River and Huihe River flow through Kaifeng and Shangqiu respectively.

3. Haihe River System

The main rivers of Haihe River system are Weihe River, Tu Hai and Ma Jiahe. Among them, the domestic drainage area is1.53x104km2, accounting for 9.2% of the total area of the province.

Weihe River is the largest river in Haihe River Basin of Henan Province. Originated in Duohuo Town, Lingchuan County, Shanxi Province, it flows through Jiaozuo and Xinxiang in Henan Province and enters Hebei Province from Nanle. The river above the provincial boundary is 286km long and the drainage area is 129 1 1km2. The average discharge of Weihe River for many years is 59.3m3/s (Yuancunji Hydrological Station). The main tributaries are Qihe River, Zhanghe River, Tanghe River and Anyang River.

4. Yangtze River system

The drainage area of Hanjiang River system in the Yangtze River basin of Henan Province is 27370km2, accounting for 16.7% of the whole province. The main tributaries are Tanghe River, Baihe River, Turbulent River and Danjiang River. Every river originates from the hilly area in the north, with short source and rapid flow. When the flood season suddenly comes, the river channel can't discharge, which often causes disasters in the lower reaches of Tanghe River and Baihe River.

Baihe originated in Yuhuangding, Songxian County, flowing through Nanyang and leaving Xinye Province. The length of inland river in the province is 302km, and the drainage area is 12 142km2.