Figure 7 depicts the annual observed runoffs at the Guide, Lanzhou, Toudaoguai, Sanmenxia, Huayuankou, and Lijin hydrological stations from 1956 to 2010. Table 4 lists the mean runoff values of different decades and percent changes compared with the 1960s for all the stations. A decreasing trend was observed over time after the 1980s, especially at the three stations below Toudaoguai station. The minimum annual runoffs of all these stations occurred after 1990. The runoff trends at the Lanzhou and Lijin stations increased after 2000.