Author

David Aled Jones

Date

August 2007

Project Type

MSc Thesis

Subject

Geology

Datasets

OS Historic County Series

Sources: Digimap

Dates/Editions: 1st Revision

Scales: 1:10,560

Related Subjects

History

Key Words

Hydrogeology; Groundwater

Publishing Institution

School of Earth and Ocean Sciences, Cardiff University

Summary

The hydrogeological understanding of the Carboniferous Limestone aquifer near Rest Bay, and the mechanisms responsible for the groundwater quality deterioration observed are poorly understood.

Based on a review of previous studies an initial conceptualisation of the hydrogeological system was generated, which in conjunction with a critical review of previously collected data highlighted the need for further groundwater level and quality data, and a greater understanding of the geological structure.

A 3 month data collection exercise was undertaken between May – August 2007, to assess the spatial and temporal changes in groundwater level and quality and to collect further information on the geological structure.

Groundwater levels were found to be spatially variable, with the majority responding semi-diurnally to tidal pressure upon the aquifer and also responding to rainfall events. Groundwater quality was also spatially and temporally variable, with the worst quality generally observed in boreholes which had been subjected to abstraction.

Based on the available data the mechanism of quality deterioration was identified as the natural fluctuation of the fresh/saltwater interface beneath the site in response to tidal changes and variability in the freshwater discharges through the system. The primary control on the distribution of groundwater levels and quality is the presence of fractured/fissured horizons intercepted by the boreholes and their connection with the brackish transition zone of the fresh/saltwater interface.

An updated conceptualisation has been generated but the hydrogeological understanding is still incomplete due to the lack of information on the presence and orientation of the fractured/fissured horizons. Further investigation is needed to better understand these horizons and their control on the system.

Aims & Objectives

Historical maps were used as part of the desk study process to investigate the possible former land uses of the study area from late 19th Century to present day. The aim was to investigate if there had been any land uses which may have contributed to the groundwater quality deterioration recorded within the study area.

Results/Outcome

Extract from Chapter 3, highlighting the historic map used:

3.2 Land Use

The golf course opened in 1895. The surrounding area has undergone little change with time, with the predominant land-use still comprising open fields. An early historic map from 1900 (Fig.3.3) shows the golf course and the undeveloped nature of its surroundings. The Rest convalescent home is present and there is also a small quarry located to the immediate west of the home

Between 1900 and 1971 the only significant change recorded is the development of the golf clubhouse, which appears by 1918, and the appearance of a few properties to the east and south east of the study area.