The climate data from 120 meteorological stations inside and closed to the study basin (Figure 1) were obtained from the China Meteorological Administration (CMA). The data set is available from 1960 to 2000 with the daily precipitation, daily mean temperature, daily maximum and minimum temperatures, daily mean surface relative humidity, daily sunshine duration, and daily cloud amount. Several stations on the Qinghai-Tibet Plateau were established from the end of 1950s, limiting the study period from 1960 to 2000 (Liu and Chen, 2000).
Six major hydrologic gauges at the main stream of the Yellow River, Tangnaihai, Lanzhou, Toudaoguai, Sanmenxia, Huayuankou and Lijin stations (Figure 1) were collected from Hydrological Year Book by the Hydrological Bureau of the Ministry of Water Resources of China (ICW , Information Center of Water Resources).
The watershed above the Tangnaihai station is the source region of the Yellow River. The water withdrawals from the river are limited in this region. The Toudaoguai station is after two large irrigation districts (Qingtongxia and Hetao IDs). The Lanzhou-Toudaoguai section is a "net" water consumption zone of the Yellow River, i.e. the annual discharge at the Toudaoguai station is less than the discharge at the Lanzhou station. The drainage area between Toudaoguai and Sanmenxia station is located on the Loess Plateau and is in a transitional zone from semi-arid to semi-humid climate. The Huayuankou station is another key station at the main stream. The annual discharge at this station reaches its maximum value. The Lijin station is the last hydrological station before the river emptying into the Baohai Gulf. Between Huayuankou and Lijin station, the runoff into the river channel is slight because the elevation of the riverbed is higher than the land surface behind artificial levees. In addition, there are large irrigation districts in the lower reach, which are located outside the watershed and channeled river water (Chen et al., 2002; Fu et al., 2004). It is another "net" water consumption zone of the Yellow River.
The data related to irrigation was collected from the Yellow River Conservancy Commission (YRCC , Yellow River Conservancy Commission; YRCC , Yellow River Conservancy Commission) and publications from previous researches (Liu and Zhang, 2002; Yang et al., 2004; Xia et al., 2004). The data included annual or decadal irrigation area and river water consumption in upper, middle, and lower reach of the Yellow River.
The vegetation condition index leaf area index (LAI) was obtained from Myneni et al. (1997). The LAI data set is available with monthly temporal frequency and 16×16 km spatial resolution from 1981 to 2000.