“水文测站暂行规范”明确的规定了输沙率测验及单位水样含沙量取样的目的。其中说明:“输沙率测验是控制性的在于精确测定通过测流断面的实际输沙率并据以计算断面平均含沙量”。单位水样含沙量取样的目的存于纪录河流含沙量的变化过程,再根据它和断面平均含沙量的关系,计算流经某一断面的输沙量。因此,单位水样含沙量应有足够的取样次数, “Hydrologic Station Provisional Code ” clearly stipulates the purpose of the sand transport rate test and the sample water content of sediment. It states: “The sediment transport rate test is controlled by the precise determination of the actual sediment transport rate through the cross-section and the calculation of the mean sediment concentration”. The purpose of sampling the sediment concentration per unit of water is to record the change of sediment concentration in the river, and then calculate the sediment discharge through a section based on its relationship with the average sediment concentration. Therefore, the unit of water sample sediment should have enough sampling frequency,