About the Project
Highlights:
· Opportunity to combine practical field hydrogeology with numerical modelling;
· Develop scenarios for water movement through a quarried catchment to assess the implications of changing climate and local variations in stratigraphy.
Overview:
Quantifying water movement through limestone catchments is challenging: water flows can vary markedly over small distances, reflecting the nature of the substrate and changes in water delivery (Bodin et al. 2022). These challenges are increased by anthropogenic activities, particularly current and historic quarrying which can impact the direction and quantity of preferential / conduit flow (e.g. Hobbs & Gunn, 1998; Lolcama et al., 2002). Globally, limestone is important as a source of aggregate and as a raw material used in the manufacture of cement, fillers and many other products. Most limestone is sourced from large open-pit quarries and in many cases, (ground)water management is a significant constraint on mining activities. Quantification of the hydrogeological effects of these activities is complicated by the extent to which most carbonate rocks have been subject to karstification and the highly heterogeneous nature of karst groundwater systems which typically exhibit marked non-stationary and non-linear hydrological behaviour (Banusch et al. 2002; Gunn & Bradley, 2023; 2024). Further complexity is present where limestone weathering results in ‘ghost-rock’ groundwater systems (Dubois et al., 2019). While considerable effort has been devoted to developing karst groundwater flow models (Jeannin et al. 2021), there are many uncertainties in quantifying the hydrogeological impacts of quarrying in limestone catchments, in particular: i) quantifying groundwater flow towards large quarried voids; and ii) assessing the impacts of dewatering operations undertaken to allow rock extraction to continue below the local level of inundation. Conversely quarrying activities provide timely and important opportunities to characterise limestone hydrogeology, with long-term (up to 40 years) data on pumping, discharge and climate that enable changing dynamics of karst water movement to be investigated: whether reflecting climate change (e.g. changes in rainfall intensity; seasonality; evapotranspiration; recharge), or quarry development (opening new faces; quarry deepening; changes in surface land use / management).
Study area:
Dove Holes Quarry is situated c. 5km NE of Buxton, Derbyshire, close to the northern edge of the Carboniferous limestone outcrop. The quarry, operated by the studentship sponsors CEMEX, is one of the largest limestone quarries in the UK with a total area of c.1.6km2. It has grown from an amalgamation of five earlier quarries with a history of extraction dating back >200 years. The quarry provides a challenging environment for hydrogeological modelling. The spatial extent of the quarried void is largely fixed and future development at the site will require an increase in depth. Since the 1990s operation of the site has required dewatering and an important consideration for the operators is its future variability given increasing volumes of water entering the site due to climate change and increased depth of mineral extraction. There is a large body of data on groundwater elevation in boreholes, rainfall and off-site discharge and water tracing experiments have been undertaken.
Aims & objectives
This PhD studentship aims to address the research challenges involved in characterising and modelling karst groundwater systems with reference to a quarried limestone catchment in the Peak District, Derbyshire, UK.
The objectives are to:
· Use a variety of data-sets to understand the hydrogeology of Dove Holes Quarry, characterising weathering features exposed in quarry faces, and investigating preferential / conduit flow;
· Develop hydrogeological models of varying complexity to derive scenarios considering the impacts of changing climate;
· Assess the hydrological impacts of quarry development, and investigate options to mitigate these impacts.
Methodology
The student will work with a supervisory team (Hydrogeologists: Gunn, Pointer, Sun & Tellam; Hydrologist: Bradley) to test and apply a suite of hydro(geo)logical tools to consider:
1. Are piezometer water levels useful in monitoring water flow in karstic recrystallised limestones?
Exploring relationships between pumping & discharge and how to upscale.
2. What is the relative utility of observations of excavated faces and observations in boreholes
Can we quantify the ‘face’ as a boundary condition; micro-monitoring; thermal / video imaging; downhole logging; inter-borehole tracer testing
3. Is it possible (or feasible) to predict the probability of encountering a conduit or a zone of enhanced permeability
Drone photogrammetry and AI recognition; correlate with fracture patterns
4. At what scale should groundwater flow in karstic limestones be interpreted if we are to predict water inflow?
There will be opportunities to work with CEMEX on-site at Dove Hole, with access to teaching resources from Birmingham’s leading Hydrogeology MSc.
