Diploma Thesis

Simulations of temperatures in heterogeneous streambed sediments - implications for temperature-based water flux calculations

Christina Schornberg (04/2010)

Support: Jan Fleckenstein

Nearly all streams and rivers in temperate climates interact with groundwater. They typically gain water and solutes from the groundwater system. On the other hand, stream water enters the streambed sediments driven by bedforms. Detailed knowledge on the flow paths of water in the streambed is especially important in contaminated areas. The flow of water mediates the transport of oxygen and contaminants and may therefore influence biodegradation. Increasingly, natural temperature differences between streams and groundwater are used to trace and to quantify water fluxes in streambeds. The temperature-based methods usually assume uniform, vertical flow and homogeneous sediments. To date the influence of streambed heterogeneity and non-vertical flow paths on streambed temperatures is still poorly understood and needs further investigation. Moreover, water flux estimation methods based on the assumption of vertical flow in the streambed would benefit if the errors originating from assuming strictly vertical flow could be quantified. Objective: Assess the influence of non-vertical flow and heterogeneous sediments on the distribution of streambed temperatures and on the evaluation of temperature-based flux estimation methods by numerical modelling. The work will include: 1. Set up of a numerical model using the code HEATFLOW 2. Investigate the effect on streambed temperatures for different scenarios of flow conditions and heterogeneities 3. Evaluation of the errors that are introduced to flux estimates when sediments are heterogeneous and the flow is non-vertical The project is a theoretical modelling study. It will provide a theoretical background in numerical flow and heat transport modelling, in particular at the interface between ground- and surface water. We are seeking a motivated and self-reliant Diplom / Master's candidate with a background in Hydrology, Hydrogeology, Environmental Science or related fields. First experiences with numerical flow and transport modelling are required. Work will primarily be carried out at the Department of Hydrogeology, Helmholtz Centre for Environmental Research – UFZ, Permoserstraße 15, D-04318 Leipzig. Contact: Jan Fleckenstein, jan.fleckenstein@uni-bayreuth.de Tel: +49 921 55 2147 Christian Schmidt christian.schmidt@ufz.de Tel: +49 341 235 1986 Edda Kalbus edda.kalbus@ufz.de Tel: +49 341 235 1806