Proglacial and subglacial aquifers: their evolution under climate change and the potential impacts in terms of resources and natural hazards, through the case of eastern Iceland

Informations projet

IceAq

N° de convention de subvention: 885891

DOI

10.3030/885891

Projet clôturé

Date de signature de la CE 5 Mai 2020

Date de début 1 Avril 2021

Date de fin 31 Mars 2023

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 184 239,36

Contribution de l’UE

€ 184 239,36

Coordonné par

HASKOLI ISLANDS
Iceland

Periodic Reporting for period 1 - IceAq (Proglacial and subglacial aquifers: their evolution under climate change and the potential impacts in terms of resources and natural hazards, through the case of eastern Iceland)

Période du rapport: 2021-04-01 au 2023-03-31

Résumé du contexte et des objectifs généraux du projet

The research on glacier evolution under climate change addresses changes in mass balance and related impacts on basal and downstream hydrology. However, consequences on groundwater are often not considered even though evolving knowledge of groundwater recharge, discharge and storage is essential for the provision of forecasts regarding water resources’ evolution and water-related risks under climate change. The EU-funded IceAq project intends to achieve an operational understanding of lesser-known aquifer systems in a glacial context and predict their hydrodynamic reactions to climate change. It will also investigate the potential glacier–aquifer interactions in deep recharge and formation of offshore fresh groundwater stocks in coastal areas. The project will focus on four outlet glaciers in eastern Iceland using existing data from geology to climatology and collecting new data on the field.

The research addressing glacier evolution under climate change is well developed, looking not only at changes in mass balance, but also at the associated effects on basal and downstream hydrology. However, aftermath changes to the groundwater component are rarely considered, even though evolving groundwater recharge, discharge and storage will be required to forecast the evolution of water resources and of water-related hazards under climate change. This knowledge gap is the object of IceAq.
IceAq will focus on 4 outlet glaciers of the Vatnajökull, the main icelandic icecap, which retreat under climate change is already documented. In addition to gathering of existing data (from geology to climatology), new data will be acquired on the field, mainly to characterise groundwater. Based on those data-sets, local comprehensive numerical models will be build, and then be integrated into a regional one, which will allow more realistic hydrogeological simulations, and the input of future climate scenarios.
The scientific perspective is threefold: achievement of an operational understanding and quantification of unknown or poorly known aquifer systems in glacial context, prediction of their hydrodynamic response to climate change, and exploration of the potential role of glacier-aquifer interactions in the mechanism of deep recharge and formation of offshore fresh groundwater stocks in littoral zones.
Outputs of the project will provide first answers to those interrogations, and be disseminated in the scientific community but also to the general audience through a participatory approach. The developed methodology will be applied in the future to other glaciated systems in different contexts.
Dr Vincent and the glaciology group of IES, UoI, have very complementary expertise, essential for this project. The planned research and training is expected to allow Dr Vincent to reach her career objectives and will offer her host new opportunities for interdisciplinary collaborations.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

To answer these questions I have:
(i) Acquired new data since May 2021 on groundwater level, temperature and electro-conductivity (EC) in an observation network of 18 boreholes including 4 newly drilled ones;
(ii) Analysed existing and newly acquired data to obtain the extent and thickness of the geological formations (from geological and drilling data), the recharge rates (from existing data: glacier mass balance and weather data) and hydraulic parameters (from existing grain size data, new slug tests and new groundwater level data);
(iii) Established a hydrogeological conceptual model of the system based on all the data;
(iv) built and run a hydrogeological numerical model of the Flàajökull area.

Main results:
Two distinct aquifers and their hydraulic conductivities are identified, with different hydrodynamic behaviour. We demonstrate the glacial melt recharge impact on the groundwater dynamic, and identified a local upward leakage from the basalt aquifer to the till and glacio-fluvial aquifer (around borehole FLA4), when the water level in the till and glacio-fluvial deposits aquifer is lower than the piezometric level in the basalt aquifer. The hypothesis of the presence of a clay layer between the subglacial till and the basalt, and also between the till and glacio-fluvial deposits and the basalt formation, would explain the separation of the two aquifers, and the confined character of the basalt aquifer observed in some locations.
Aquifers characteristics Till and glacio-fluvial aquifer Basalt aquifer
Hydraulic gradient [4 – 5/1000] [3 – 30/1000]
K hydraulic conductivity, m s-1 [4.5E-6 – 3.7E-5] [1E-10 – 4.9E-6]
Sy specific yield [0.01 – 0.12] [0.02 – 0.11]

A comprehensive water balance at the scale of the watershed has been obtained. Water available for surface flow and groundwater recharge is 4 times higher under the glaciers than on the plain, and for the subglacial part varies temporally (for 2021 maximum in July and August about 960 mm month-1, and minimum in April and November, about 160 mm month-1) and with the elevation (highest at the lowest glacier elevation 6800 mm year-1 in 2010, lowest at the highest elevation: less than 2000 mm year-1 in 2010).

A first paper is presenting these results (preprint, revision in progress: https://doi.org/10.5194/egusphere-2022-1442) and 4 data sets gathering all the data acquired during IceAq project are openly accessible (IceAq - Slug Tests Data (https://zenodo.org/record/7716507) IceAq Groundwater Hourly Data (https://zenodo.org/record/7716453) IceAq - groundwater data, monthly manual data (https://zenodo.org/record/7716362) IceAq – GPR profiles data (https://zenodo.org/record/7773783).

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Demonstration of the existence of a deep aquifer in the fractured bedrock in several catchments headed by glaciers;
Hydrodynamic characterisation of both the shallow and deep aquifers;
Demonstration of the importance of subglacial recharge to aquifers in contexts involving warm-based glaciers lying on sediments and/or fractured bedrock. It is thus important to include the groundwater compartment to evaluate accurately the water balance of glacierised catchments;
Quantification of the amount of glacial meltwater available for surface flow and groundwater recharge, and its temporal and spatial variability.

These results are important steps in filling the knowledge gap on the glaciers-aquifers interactions and how they will be impacted by climate change.
They are paving the way to forecast the evolution of available water resources for local populations and hydropower production, as well as flooding, landslide and seismic hazards, in similar catchments around the globe.

conceptual-model-iceaq-v4b.jpg