Hydrological characteristics and causes in southwest China.

In the concept of China's natural zoning, the southwest region includes the vast hinterland of southwest China, including the southeast of Qinghai-Tibet Plateau, Sichuan Basin, Qinba Mountain Area and most of Yunnan-Guizhou Plateau. The corresponding administrative divisions generally include Sichuan, Yunnan, Guizhou, Chongqing, most of Xizang Autonomous Region and southern Shaanxi.

topography

The terrain in southwest China is complex, but it is obviously divided into three terrain units:

1. Sichuan basin and its surrounding mountains. The main scope includes most of Chongqing, central, eastern and southeastern Sichuan Province, and southern Shaanxi Province.

The second is the mountainous and hilly areas in the middle and high mountains of Yunnan-Guizhou Plateau. The main scope includes the whole territory of Guizhou Province and the southern, central and eastern parts of Yunnan Province. Third, the mountainous areas of the Qinghai-Tibet Plateau. The main scope includes Tibet, northern, western and southwestern Sichuan Province and northwestern Yunnan Province.

Rivers and lakes

Rivers-There are many rivers in this area.

The rivers in the Yangtze River basin are the main rivers in the north-central part of this area. The south and west belong to the Pearl River Basin, Yuanjiang River Basin, Lancang River Basin, Nujiang River Basin, Irrawaddy River Basin, Ganges River Basin and Indus River Basin respectively. In addition, there are many inland rivers flowing into large and small plateau lakes in the inland areas of northern Tibet.

2. Lakes-The lakes in this area are mainly plateau lakes, which are basically concentrated in three areas:

1. The plateau lake area in northern Tibet, including parts of Ali, Naqu and Xigaze in Tibet, mainly represents Namco Lake;

2. Lake-intensive areas in the central Yunnan Plateau, including areas south of Kunming in central and southern Yunnan, mainly represented by Dianchi Lake and Fuxian Lake;

3. The distribution of plateau lakes in northwest Yunnan, including the inland areas of Yunnan Province north of Dali, with Erhai Lake and Lugu Lake as the main representative lakes.

Climate and agriculture

Corresponding to the topographic region, the climate in southwest China is mainly divided into three categories:

1. The humid monsoon climate in the north subtropical zone of Sichuan Basin. Mild climate, high humidity, foggy and gentle terrain. It is an area with concentrated agriculture and population. Chengdu, Nanchong, Chongqing and other big cities are located here. The second is the subtropical monsoon climate of Yunnan-Guizhou Plateau in low latitude. The low latitude plateau is an excellent hotbed for producing a climate with four seasons like spring. The representative cities with spring-like seasons are Kunming and Dali. Mountain areas are suitable for developing forestry and animal husbandry, while dam areas are suitable for developing agriculture, flowers, tobacco and other industries.

Three, the alpine climate and three-dimensional climate distribution area. This is a major animal husbandry area.

In addition, there are several tropical monsoon forest climatic zones at the southern end of the region, with distinct wet and dry seasons. Xishuangbanna is a representative area, producing more rubber and tropical fruits.