坝下河道水生物栖息地的生态恢复研究

Research on ecological restoration of aquatic habitats in downstream

河道内砂砾滩形态发挥着重要的河流生态作用,水库下游河道沉积物相对有限,砂砾积累构建砂砾滩可作为恢复河道下游生态系统的重要手段。作者进行现场生态水文数据及地貌形态分析,提出河道水生物栖息地生态恢复方法,在北方水库夏季洪峰冲击作用下,顺水流沉积,形成砂砾浅滩。通过测定水温、悬浮颗粒有机质浓度、水力梯度及基流条件下砂砾滩周边浅水宽度等特征值,分析动态构建的砂砾滩及物理塑造沙岛的生态功能属性。结果显示,该水生物栖息地修复方法通过增加夏季基流中水力梯度、潜流交换率和悬浮颗粒有机质的保留率,修复河床基质渗透性,同时延长河道浅水层湿度边界范围,结合粗沙积累效果,增加河道形态复杂性,改善潜流交换效率和悬浮颗粒有机质浓度,最终加强流域内温度的异质性,修复河流水生物栖息地的生态功能。

River gravel accumulation plays an important role in ecological restoration in rivers,but sediment in downstream of reservoir is very limited. Strengthen the accumulation of gravel is important means to river ecological restoration. Aquatic habitat restoration method is studied in this paper. Water temperature,concentration of suspended particles of organic matter,hydraulic gradient and shallow width are analyzed. Functional attributes of dynamical gravel bar and physical point bar are studied. Results show that gravel restoration can increase hyporheic exchange by increasing hydraulic gradients at base-flow,refreshing bed materials to enhance substrate permeability,and elongating the wetted boundary length in shallow waters. Study results suggest that mechanically created channel geomorphic features combined with sediment accumulation can increase channel complexity,driving hyporheic flow and increasing suspending partical organic material retention,thus ultimately resulting in temperatureheterogeneity and ecological restoration.