Domestic. 9. 10% Domestic. 11.30% Industry, 13% Industry, 20.80% Whole country Figure 5 Composition of water us China compared with the whole country 77-9% of the total water use in this region-10% higher than that in the whole country, and indicates a lower level of urban and industrial development in this region Water environmental problems due to water shortage In north China, over withdrawal of water is a common problem in the densely populated city areas or extended irrigation areas. The direct result of over withdrawal is a decrease of water flow in a river channel and/or a decline of groundwater table. As discussed in the for- mer sections. the Yellow River in north China is one of the river basins with a low rainfall but high percent water withdrawal. As is shown in Figure 6, from the early 1970s, increased withdrawal of water from the main channel of the river began to result in a vast decrease of the river flow. In 1972, for the first time, no water was flowing in the river channel for 19 days. Then, in the following years up to 1999, there were 2I years when occasional or extended "flow-cutoff'occurred. The situation became worse in the sever years from 1992 to 1998, with 1997 as the worst year for flow-cutoff to continue from Feb. ruary 7 to December 23 for as long as 226 days in the lower reach of the river. The main reason for the flow-cutoff is the concentrated pumping of water from the river for various water uses especially irrigation use. The total quantity of water withdrawal from the whole river channel could be up to 6,000 m/s, of which approximately 4,000 m/s were from the lower reach. This amount is far beyond the regular flow rate of the river A similar condition is also noticed in other river basins. Figure 7 illustrates the vari- ation of annual fow in the middle reach of weihe river from 1990 to 2002. The Weihe River is the largest tributary of the Yellow River and flows through the Guanzhong Plain where the ancient capital city xian ted. a sudden decrease of the total annual flow occurred in 1994 and it continued to be of a much lower value compared to the Figure 6 Days with flow-cutoff in the lower reach of the Yellow River from 1972 to 1999(data source: Yellow River Committee, 2004)77.9% of the total water use in this region – 10% higher than that in the whole country, and indicates a lower level of urban and industrial development in this region. Water environmental problems due to water shortage In north China, over withdrawal of water is a common problem in the densely populated city areas or extended irrigation areas. The direct result of over withdrawal is a decrease of water flow in a river channel and/or a decline of groundwater table. As discussed in the for￾mer sections, the Yellow River in north China is one of the river basins with a low rainfall but high percent water withdrawal. As is shown in Figure 6, from the early 1970s, increased withdrawal of water from the main channel of the river began to result in a vast decrease of the river flow. In 1972, for the first time, no water was flowing in the river channel for 19 days. Then, in the following years up to 1999, there were 21 years when occasional or extended “flow-cutoff” occurred. The situation became worse in the seven years from 1992 to 1998, with 1997 as the worst year for flow-cutoff to continue from Feb￾ruary 7 to December 23 for as long as 226 days in the lower reach of the river. The main reason for the flow-cutoff is the concentrated pumping of water from the river for various water uses especially irrigation use. The total quantity of water withdrawal from the whole river channel could be up to 6,000 m3 /s, of which approximately 4,000 m3 /s were from the lower reach. This amount is far beyond the regular flow rate of the river. A similar condition is also noticed in other river basins. Figure 7 illustrates the vari￾ation of annual flow in the middle reach of Weihe River from 1990 to 2002. The Weihe River is the largest tributary of the Yellow River and flows through the Guanzhong Plain where the ancient capital city Xi’an is located. A sudden decrease of the total annual flow occurred in 1994 and it continued to be of a much lower value compared to the Figure 5 Composition of water use in north China compared with the whole country Figure 6 Days with flow-cutoff in the lower reach of the Yellow River from 1972 to 1999 (data source: Yellow River Committee, 2004) X.C. Wang and P.K. Jin 40