ESR N° 2: Flow and reactions in stream-riparian zone systems

Research fellow: Guilherme Nogueira
Profile
Profile

hosted at Helmholtz-Zentrum für Umweltforschung UFZ – Leipzig, Germany

Supervisors
Fleckenstein, Jan H. – UFZ
Werban, Uli – UFZ
Schmidt, Christian – UFZ

Secondments
UNINE Neuchatel – 3 months (2018)
UCPH Copenhagen – 3 months (2019)

Research Objectives

Identify and characterize the space and time patterns of exchange between streams and their riparian zone and the resulting potential for solute turnover by jointly using novel and advanced tracing, imaging, and modelling techniques.

Project description

This ESR project aims at understanding the links between physical controls (e.g. stream stage, subsurface hydraulic conductivity and heterogeneity) and biogeochemical process patterns (space and time patterns of reactivity) in riparian aquifers.

At the River Selke TERENO field site, the natural EC contrasts between stream water and groundwater can be used to trace stream water intrusion into the riparian aquifer. Temporal dynamics of stream-groundwater exchange will be derived by analysis of time series of conservative solutes like EC measured in the stream and piezometers in the riparian aquifer. In close conjunction, spatial infiltration into the riparian aquifer will be imaged using ERT surveys that are optimized for the detection of natural EC contrasts. Using the identified patterns of water and solute fluxes and additional measurements of O2, NO3 in the stream and piezometers with varying distance to the stream will enable a mapping of the turnover capacity for reactive solutes in the riparian aquifer.

A synthesis of the observations will be achieved using a reactive transport model to replicate flow and reactivity patterns. The systematic joint evaluation of temporal dynamics and spatial patterns of flow and reactivity with state of the art imaging and sensing methods and models is a novel approach to investigate reactive potential of riparian aquifers.

Collaborations on geophysical and thermal imaging techniques are planned with ESRs 6, 7, 12, 13.

Tasks and methodology

Conduct tracer tests making use of conservative and reactive compounds together with ERT measurements under diverse conditions (e.g. different river discharges and seasons) with the aim to characterize and better capture dynamics of the system; Hydrogeological tests to characterize general heterogeneity of the riparian zone and time series analyses (i.e. EC, water level, O2) to link different features and resulting reactivity.

Data & Datasets

Data related to Guilherme’s research project will be soon available on the UFZ Data Management Portal.

Dissemination & Communications

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EGU 2019 General Assembly, Vienna (poster): Flow dynamics and resulting reactivity in the transition zone between streams and riparian aquifers

4th Cargèse Summer School, 2018 (poster) : Imaging flow dynamics and resulting reactivity in the transition zone between streams and riparian aquifers

Glossary

Riparian Zone – Adjacent zone to a river/stream or other water body, which can vary in time and space according to local hydrogeological and climate characteristics.

ERT (or ERI) – Electrical Resistivity Tomography (Imaging): geophysical investigation method that uses different combinations of electrodes arranged in lines or grids to image the subsurface in 2D or 3D surveys. ER methods are used to determine subsurface electrical resistivity by injecting low frequency electrical currents (<1 kHz) into the ground and measuring the resultant voltage between two or more potential electrodes.