三峡水库运行初期库区糙率特性分析

Analysis of Roughness Property of Three Gorges Reservoir in Initial Operation Period

为得到三峡水库实际运行后库区泥沙的淤积糙率,基于三峡水库运行10余年库区实测淤积资料、日均来流量与水位序列,采用一维水流模型推算了三峡水库正常蓄水运行以来库区沿程的综合糙率。结果表明,常年回水区峡谷段淤积较少,糙率随流量、运行时间变化较小,糙率相对较大;常年回水区宽谷段泥沙在主槽落淤后床面阻力减小,糙率逐年降低;常年回水区弯曲分汊段泥沙淤积严重,糙率逐年减小;变动回水段天然河道特性起控制作用,糙率相对稳定。同一洪水流量情况下,随运行时间推移和淤积发展,糙率总体减小。常年回水区糙率的降低值明显大于变动回水区糙率的降低值。三峡水库淤积过渡期糙率与河道部位、断面形态、河道形态等参数均存在一定关系。研究成果为三峡水库淤积与糙率的关系研究奠定了基础。

Based on measured sedimentation,daily average inflow and water level series of the Three Gorges Reservoir after 10 years operation,one-dimensional flow model was adopted to calculate sediment deposition roughness of the Three Gorges Reservoir after its actual operation.Results show that the roughness characteristics are different in straight gorge reach,straight stretch reach,bending braided reach in permanent backwater area and in fluctuating backwater area.The roughness are relatively larger and changes little according to the discharge and operation time in straight gorge reach compared with straight stretch reach in permanent backwater area because few sedimentation occurs.The roughness yearly diminished slightly in bending braided reach in permanent backwater area.However in fluctuating backwater area the roughness varied little with the impounding because the river reflects its natural property.With the reservoir operation and sedimentation the roughness generally reduced in the total backwater area with the same discharge and the roughness in the permanent backwater area diminished much more than that in the fluctuating backwater area.Furthermore analysis shows that the change of the transitional period roughness is relative to river location,section shape and channel morphology.The research results lay the foundations for study of the relationship between sedimentation and roughness in Three Gorges Reservoir Region.