Lagrangian model for invertebrate drift in streams

Downstream advection of benthic invertebrates in streams has received much attention, in the context of constant drift, and also in relation to increased flow caused by natural spates and by the release of water from reservoir hydroelectric power stations. However, model studies of the relationships between hydraulic parameters, behavior and drift are unavailable for many taxa. A recent study has shown that certain species of cyclopoid copepods - a widespread taxon and an important component of the meiobenthos - perform active counter-current swimming. They explore the entire water column at low flow velocity, but stay close to and perform frequent incursions into the sediment bed at higher flow velocities. This active behavior supposedly limits their downstream downstream drift, yet the implications for downstream drift and dispersion remain unexplored. The aim of the present study is to explore the drift behavior of invertebrates for varying flow conditions. An individual-based Lagrangian diffusion model will be set up, that is informed by existing detailed measurements of flow statistics and invertebrate behavior. A first aim is to model and reproduce drift and dispersion of invertebrates observed in the laboratory channel. In a second step, large scale behavior (i.e. river-reach scale) will be modelled. Special attention will be given on the permeable sediment bed which, next to counter-current swimming, offers invertebrates the possibilty to take shelter and avoid excessive drift.

Supervision and contact

Prof. Dr. Markus Holzner, ETH Zürich
Email:  - Tel.: +41 44 633 30 79