The use of integrated surface and subsurface hydrologic models (ISSHM) to understand the flow exchange processes occurring in stream-wetland areas may give important insights to researchers and water resource managers in terms of understanding where groundwater preferentially discharge to stream valleys. How to best monitor and quantify the surface water – groundwater interaction is a non-resolved issue. Several techniques have been proposed based on the use of heat as a tracer and they aim to provide robust and reliable results. An ISSHM of a stream-wetland area in central Jutland (Denmark) is developed in order to create a benchmark model that could better constrain the applicability of such techniques.
Event: 33rd Nordic Geological Winter Meeting 2018 Poster by Joel Tirado-Conde, Carlos Duque, Peter Engesgaard and Sachin Karan
Groundwater discharge or upwelling plays an important role in the ecological and hydrological dynamics in coastal areas, bringing fresh water inputs to saline water systems. However, locating it both in space and time as well as quantifying how much groundwater flows upward to coastal areas requires a big effort since these are very heterogeneous systems. Seasonal changes in rainfall, temperature and water level lead to temporal variability, while variations in the hydraulic properties and hydrological processes can generate spatial heterogeneity, making the process of measuring those fluxes complicated and requiring multiple measurements to obtain accurate results.
Furthermore, the non-steady position of the fresh water-salt water interface increases the uncertainty surrounding these processes. Using temperature as a tracer, the groundwater inputs to a surface water body can be calculated by means of solving analytically the conduction-convection equation, shortening considerably the amount of field work needed to obtain groundwater upwelling fluxes.
In this work, groundwater upwelling in the Ringkøbing Fjord coastal area was obtained using two methods: direct upward flow measurements and indirect flow calculations with shallow fjord bed temperature profiles. These two different sets of data are compared in order to assess their feasibility to map and quantify upwelling. Addressing the strengths and weaknesses of each method, we aim to better constrain the reliability of them in order to improve the quality of the data collection process.
Presentation by Adrien Selles, Richard Hoffmann, Wajid Uddin, Pascal Goderniaux, Alain Dassargues, Jean-Christophe Maréchal and Virendra Tiwari (2019)
Sustainable management of groundwater in fractured rocks needs accurate observation data about processes occurring in fractures and rock matrix. Dye tracer tests are commonly used for characterization of these processes.
Using temperature as a tracer is more recently used and provides several advantages, including a more detailed investigation of the geological heterogeneity and a more robust interpretation of the mean groundwater velocity. This is an important requirement for more realistic modelling of solute transport in aquifers using informative and robust reference data.
In common temperate climate aquifers, characterized by an approximate 10 °C natural background temperature, hot water injections are more and more used, while a cold water injection in hot aquifers is much more promising. This is for example the case in Southern India, with natural aquifer background temperature values around 30 °C. Cold water injections in such environments, enable to increase the difference of temperature between the injected fluid and groundwater.
By this way, cold plume transport modelling offers interesting opportunities for aquifers characterization, where heat injections are more limited because of higher natural background groundwater temperature.
Within the ENIGMA ITN program, such innovative smart tracer tests with injections of hot and cold water were applied in an isolated fracture within a weathered granite aquifer in Southern India.
The tests were performed on a test site located at Choutuppal (Telangana state). It is a scientific observatory of environmental research established within the partnership between the BRGM (Bureau de recherches géologiques et minières) in France and the National Geophysical Research Institute (NGRI) in Hyderabad, India. Based on this cooperation, over 25 borewells are accessible on a small scale.