Abstract: The river basin hydrological factors and underlying surface conditions which were affected by the climate change and human activities have been changed greatly. The sediment concentration was decreased significantly after the implementation of large-scale soil and water conservation measures in some parts of rivers. However, the river sediment presented a trend of increasing in the Shule River basin which is originated in the western Qilian Mountains in the Hexi Inland River Basin due to precipitation and human activities. The time-space distribution law of the sediment and the relationship between the sediment and the water sand were analyzed systematically by using the data from four hydrological stations which include Changmabu, Panjiazhuang, Dangchengwan, and ShaZaoyuan in Shule River Basin during the time period from the establishment of the hydrometric stations to 2012. The spatiotemporal distribution law of river sediment was analyzed using hydrologic statistics. The annual sediment discharge of the main stream of the Shule River at Changmabu station is 333.5×104 t and it is then reduced to 223.5×104 t at Panjiazhuang station in the downstream. The annual sediment discharge of the Danghe River is 76.56×104 t at Dangchengwan station and it was then increased to 121.3×104 t at Shazaoyuan station in the downstream. The sediment discharge mainly happened in the flood season from July to August in the main stream of Shule River, which accounted for 81.9%～84.0% of its annual sediment discharge. The sediment discharge of the Danghe basin mainly happened from April to August, which accounted for 92.3% of its annual sediment discharge. The sediment change trend was analyzed using Kandel rank correlation, Berman rank correlation and linear trend correlation. The sediment mutation is analyzed by the Man-endall method, order clustering method, Lee- eghinan method. The results show that the change of sediment in the basin indicated an increasing trend and annual sediment charge was increased by 86.3%～148.2% after the mutation point in 1998. At the Panjiazhuang station, the relation model between precipitation and sediment, the relation model between runoff and sediment, and the relation model among annual sediment discharge, annual runoff, and annual maximum peak flow were established by using the method of linear correlation and nonlinear complex correlation and the result showed high correlation coefficients ranging from 0.717 to 0.858. Above the valley outlet, the precipitation is the main factor for the coming water and sediment. In order to reduce the soil erosion, the relevant authorities or departments should take actions to increase the soil and water conservation in the upstream areas, by implementing the ban on reclamation, mining and grazing, and preventing over-exploitation. Below the valley outlet, the water sediment is mainly influenced by human activities such as building reservoirs, constructing hydropower station, as well as water diversion engineering project and sand excavation in river courses. The water quantity in the downstream reaches is sharply reduced or depleted. The desertification of the Gobi Desert is serious and the ecological environment is deteriorated. The ecological water quantity should be appropriately increased in the middle and lower reaches in order to improve the ecological environment. With the increasing attention to the Qilian mountain and the Hexi corridor in the inland river basin, the choice of the Qilian mountain as the national park system pilot and the implementation of the national river chief system, the river ecosystem health has been on the agenda. It has significance to study the watershed sediment distribution laws and water sediment relations to help execute the strategy of the western ecological security, and restore the regional ecological environment, and sustainably utilize water resources.

Key words: sediment, distribution law, trend variation, runoff-sediment relationship, Shule river