About the Project
Context: Coastal and island aquifers are important sources of potable water for millions Worldwide. Management of this resource requires an understanding of the dynamic relationships between meteoric recharge, evapotranspiration, groundwater discharge and aquifer salinisation. Aquifer hydraulic conductivity plays a key role in controlling the size of the freshwater lens and location of the saline interface1. However in limestones hydraulic conductivity is strongly scale-dependent, and is particular challenging in young limestones where karstification overprints significant matrix porosity and permeability2. This complexity means that neither analytical solutions nor numerical models based on homogeneous rock properties can reliably predict the distribution of freshwater1. It is within this context that we are faced with the critical challenge of managing coastal and island aquifer systems under conditions of rising global sea level and increased intensity and frequency of storms.
Hurricanes are an important source of recharge to aquifers, but in low-lying areas storm surges can flood the aquifer with seawater. Extensive salinisation of the surficial aquifer occurred in low lying areas of North Andros Island after Hurricane Frances in 2004, and just last year Hurricane Dorian generated an estimated 7 m storm surge over the northern Bahamas. This project will focus on North Andros Island, formerly the major source of freshwater to almost 70% of the population living on nearby New Providence, where available hydrological data extends back some 50 years3. Supplementing historic groundwater and climate data with hydrogeological monitoring using a bespoke network of wells, this project will seek to characterise the dynamics of the freshwater system and response to future climate change and anthropogenic impacts, from groundwater abstraction to potential aggregate mining.
Approach: Fieldwork will be undertaken to evaluate the current state of the freshwater lens and establish a monitoring network and programme for data collection (with local support). Historic and recent data will be analysed in the context of natural and prior anthropogenic stresses including secular changes in recharge, episodic hurricanes, land-use change (afforestation/deforestation) and historic groundwater extraction. This analysis, together with stratigraphic data and hydraulic conductivity measurements, will provide the foundation for construction of variable density groundwater flow models. Preliminary 2D axisymmetric simulations will inform the development of 3D models. Forward modelling will then estimate the range of possible impacts of projected climate change scenarios including the sea-level and tropical storms, as well as of alternative mining proposals (areas, rates of development, depth of working), including post-mining recovery.
Requirements: This project requires an upper second, or first class BSc or MSci in physical geography, geology or engineering sciences, and/or an MSc at Merit or above in a relevant discipline. The student should be highly numerate, have some knowledge of coding and/or experience of using models in Earth Sciences, and also be willing to conduct hydrogeological fieldwork in remote areas of the Bahamas. Experience of hydrogeological data analysis and modelling is a significant advantage. The successful candidate will have strong communication skills to integrate with collaborators (including with parallel PhD studies in hydrogeophysics and carbonate sedimentology/diagenesis) and to communicate with stakeholders.
Training: The successful candidate will join an internationally renowned research team in the School of Earth Sciences at the University of Bristol, and work within the Cabot Institute. Training will be provided in carbonate sedimentology and diagenesis, field hydrogeology (with an anticipated first field season summer 2021), and numerical modelling of coastal aquifer hydrology. The student will be encouraged and supported to produce a series of research publications during the study.
Funding: This project is supported by Bahamas Material Company. Funds will cover the student stipend, fees and research costs for four years from March/April 2021. Because of the level of funding available, this project is offered to UK and EU students but cannot be offered to international students.
Further information: please contact: Prof. Fiona Whitaker: [email protected]
School of Earth Sciences:
How to apply to the University of Bristol: http://www.bristol.ac.uk/study/postgraduate/apply/
Please select PhD in Geology as the programme in the online application system.
1.Costall A. et al. (2020) Groundwater throughflow and seawater intrusion in high quality coastal aquifers. Scientific Reports 10, 9866. https://doi.org/10.1038/s41598-020-66516-6
2.Whitaker F. & Smart P. (2000). Characterising scale-dependence of hydraulic conductivity in carbonates: evidence from the Bahamas. J. Geochemical Exploration 69,133-137.
3.Whitaker F. & Smart P. (1997). Hydrology and hydrogeology of the Bahamian Archipelago. Developments in Sedimentology 54, 183-216.
4.Cooper K., et al. (2016) Dissolved organics, carbonate transformations and microbial community response to variations in recharge in a shallow carbonate aquifer. Biogeochemistry 128, 215-234.