Impact of Drought on Environment
In arid and semiarid regions (annual precipitation less than 400 mm), local rainfall does not meet agricultural needs. In such cases, too many withdrawals from rivers upstream could directly affect the water environment and ecosystem downstream. Environmental issues due to drought or water shortage (mainly in north China) are discussed below.
1. Drying of Land, Lakes, and Rivers
In the north China plain, the annual runoff coefficient dropped from 0.2 in the 1950s to 0.1 in the 1980s because of too many withdrawals from rivers. Most of the small and medium rivers in the north China plain have become dry intermittently. Since 1972, even the Yellow River has frequently dried up in the spring and summer. Bai Yang Dian, the famous lake of the north China plain, dried up several times in the 1980s, leading to water pollution, sedimentation, and other adverse consequences for the environment and eco systems. A similar situation occurred in the Tarim River in Xinjiang Autonomous Region and Shiyang River of Gansu Province in northwest China.
2. Environmental Degradation Due to
Lowering of the Groundwater Table
Overdraft of groundwater in the north China plain and in urban areas in the Yangtze Delta led to a significant decline of the groundwater table and an expansion of cone coverage in these areas. By the end of the 1980s, the average decline of the groundwater table of shallow aquifers in the north China plain was 8-10 m, and the decline in cone areas, covering 27,000 km2, reached as high as 20-30 m. The decline of the groundwater table has had critical environmental consequences. Land subsidence was found in cities like Beijing, Tianjin, and Taiyuan in the north and Shanghai, Suzhou, and Wuxi in the Yangtze River Delta.
Sea water intrusion in coastal areas is another environmental issue caused by the declining groundwater table. The affected area along the Bo Hai Bay for Liaoning, Hebei, and Shandong provinces totaled 1432 km2.
3. Water Pollution
With rapid economic development in China, surface water quality has deteriorated in urban and coastal areas. In the late 1980s, polluted water directly discharged into rivers in the north China plain totaled 4.3 billion tons, but the total annual runoff is only 33.8 billion m3. The ratios of polluted water to total runoff for Beijing, Tianjin, and Tangshan were even higher. In inland basins like Ta Li Mu River (Xin Jiang Autonomous Region), because of the decline of natural runoff and increase of irrigation return flow, the water is significantly alkalized, and the same situation occurred for many inland lakes in the northwest.
Continue reading here: The Changing Rate of Water Use in Different Sectors and Administrative Regions
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