黄河口现行流路入海水沙特征对流域的响应

Characteristics of flow and sediment into the Yellow River Estuary responding to upstream hydrologic processes

基于1976-2012年利津站实测水沙资料,选取1976-1986年、1987-1999年及2000-2012年作为特征时段,探讨了黄河口现行入海水沙条件变化的阶段性特征,重点研究了入海泥沙粒度特征对入海水沙变化的响应情况。结果表明:(1)与1976-1986年年均入海流量1020 m^3/s相比,1987-1999年与2000-2012年入海流量大幅度减小,分别为473.7 m^3/s和504.7 m^3/s;(2)与1976-1986年年均入海含沙量24.4 kg/m^3相比,1987-1999年大幅度减小至15.9 kg/m^3,2000-2012年仅为4.1 kg/m^3;(3)1976-1986年入海悬沙中值粒径为0.022 mm,1987-1999年减小至0.016 mm,2000-2012年又变粗至0.021 mm,反映水库正常运行一段时间后,下游河床冲刷造成入海泥沙粗化;(4)2000年后利津站与花园口站悬沙粒度特征变化趋势趋于一致。研究还揭示了利津站床沙特征与流域前4年来沙系数存在较好相关性,利津床沙粒径呈现随来沙系数减少而增大的趋势,表明流域来沙量减少会造成利津站床沙粗化。

Based on field measurements at Lijin gauging station,1976-1986,1987-1999 and 2000-2012 are chosen as typical periods to speculate characteristics of flow and sediment into the Yellow River Estuary in responding to upstream hydrologic processes.This study focuses on the variation in sediment particle size which was rarely reported.The results showed that:(1)Compared to the annual averaged discharge of 1020 m^3/s at Lijin during 1976-1986,the discharge reduced remarkably during 1987-1999 and 2000-2012,which were 473.7 m^3/s and 504.7 m^3/s,respectively;(2)Compared to the annual averaged sediment concentration of 24.4 kg/m^3 at Lijin during 1976-1986,the sediment concentration decreased significantly to 15.9 kg/m^3 during 1987-1999 and was only 4.1 kg/m^3 during 2000-2012;(3)During the study period,the highest median particle size(D50)of suspended sediment at Lijin was 0.022 mm in 1976-1986,the D50 became much finer during 1987-1999 with a value of 0.016 mm,and suspended sediments coarsened during 2000-2012 with an average value of 0.021 mm due to multi-year reservoir operation in the upstream;(4)Variation in suspended sediment particle size at Lijin had a good correlation with that at Huayuankou in the Yellow River,particularly after 2000.Moreover,it is suggested that there are good relationships between D50 of riverbed sediment at Lijin and previous 4-year averaged hydrological factors derived from the upstream hydrologic processes,indicating that riverbed sediment particle sizes at Lijin could increase accordingly in response to less upstream sediment fluxes.