Since the 20th century, many large-scale inter-basin water transfer projects have been built around the world, such as the Central Valley Project and California Water Transfer Project in the United States, the Central Asia Water Transfer Project in the Soviet Union and the Snow Mountain Project in Australia. According to incomplete statistics, there are more than 160 large-scale projects built, rebuilt or planned in the world, mainly distributed in 24 countries. These projects have become the lifeblood of local agriculture, industry, cities and people's lives.
The western United States is called the arid desert. Due to the construction of long-distance water transfer projects such as the Central Valley, California Water Transfer Project, Colorado Waterway and Los Angeles Waterway, the irrigated area in the arid valley area of California is 13340 square kilometers, making California the state with the largest population, the largest irrigated area and the highest grain yield in the United States, and Los Angeles the third largest city in the United States.
There are as many as 15 large-scale water transfer projects in the former Soviet Union, with an annual water transfer capacity of more than 48 billion cubic meters, which are mainly used for farmland irrigation. There are more than 65,438,000 research institutions of water transfer projects in China.
In order to solve the inland drought and water shortage, Australia built the first water transfer project-Snow Mountain Project 1949 to 1975. The project is located in the southeast of Australia. Through the dam reservoir and mountain tunnel network, the reservoir is built from the east slope of the snow-capped mountains to store water, and part of the excess snow water from the east slope is led to the water-needed area on the west slope. Along the way, gap (with a total gap of 760 million) is used to generate electricity for the capitals of Canberra, Melbourne, Sydney and other cities.
Pakistan's West-to-East Gas Transmission Project transfers water from West Sanhe to East Sanhe to irrigate farmland 1534 1 square kilometer. Pakistan has changed from an original grain importer to a country that exports 6.5438+0.5 million tons of wheat and 6.5438+0.2 million tons of rice every year.
The inter-basin water transfer projects that have been completed or under construction in China mainly include: Tianjin and Hebei provinces to divert Luanhe River to Tianjin and Tangshan, Liaoning Province to divert Biliu River to Dalian, Shandong Province to divert Yellow River to Qingdao, Guangdong Province to divert Dongjiang River to Shenzhen, and Gansu Province to divert Datong River to Qinwangchuan. The project of pumping water from the Yangtze River to the lower reaches of Huaihe River in Jiangsu Province will be further developed into the East Route Project of South-to-North Water Transfer. The middle route project and the west route project of South-to-North Water Transfer Project, as well as the South-to-North Water Transfer Project to introduce Songhua River water into Liaohe River, are also being planned and studied.
The benefits of water transfer are self-evident. It not only makes it possible to develop the poor water area, but also increases the vast water area, water belt and atmosphere of the water receiving area. The vertical water vapor exchange between aquifers is strengthened, and the water volume of rivers and lakes is compensated and adjusted; Water transfer helps to form the foundation of food chain and provide habitat for rare and endangered wild animals; Provide cheap and pollution-free hydropower to promote the development of shipping industry; Bringing nutrients into the water transfer system is beneficial to the production and reproduction of fish; Water transfer can enhance the purification ability of water itself and improve water quality; Diversion dams and canals in various countries have also become scenic tourist areas.
However, the negative effects of water diversion on ecology and environment, such as land inundation, population migration, pollution and diseases, are also the most disturbing. It is particularly noteworthy that the longer the distance and the larger the scale of the water transfer project, the more complex and comprehensive the impact on ecology and environment will be. For example, the North American Hydropower Union plans to flood thousands of kilometers of river valleys, some of which are the best wild resources and scenic spots in North America, and also involves international relations issues. Some water transfer projects have changed the flow direction of rivers and produced "reverse rivers", which will lead to more serious ecological and environmental problems.