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The geophysical investigation of lake water seepage in the regulated environment of the Bosherston Lily Ponds, South Wales, UK. Part 2: historical, dam‐related pathways
Author(s) -
Husband Claire R.,
Cassidy Nigel J.,
Stimpson Ian G.
Publication year - 2009
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.3997/1873-0604.2009044
Subject(s) - ground penetrating radar , geology , electrical resistivity tomography , bedrock , hydrogeology , natural (archaeology) , hydrology (agriculture) , hydraulic engineering , geophysics , geomorphology , geotechnical engineering , radar , paleontology , telecommunications , physics , engineering , computer science , electrical engineering , thermodynamics , electrical resistivity and conductivity
The detection, characterization and assessment of water loss through hydrological pathways is an important aspect of civil, hydrological and environmental engineering. At any site, variations in the form and hydrological integrity of both natural and man‐made features can play a critical role in fluid transportation through the presence of enhanced hydraulic conductivity. Traditional hydrological and invasive engineering investigation methods are often unsuitable for ecologically sensitive environments and in this paper, we report the results of a non‐invasive hydro‐geophysical study at the Bosheston Lily Ponds in Pembroke, South Wales, UK, an area classified a Special Area of Conservation (SAC). For over 30 years, the lake system has experienced unexplained water loss and the geophysical surveys focused on identifying hydraulic conduits/pathways in the underlying carboniferous limestone and assessing the integrity of the man‐made dam structure at the outlet of the lake system. The site is managed under tight regulatory regime that limits the scope and extent of any hydrological/geophysical investigations. The main objectives were to determine whether bedrock fracturing is promoting natural water loss and, more pertinently, if structural failures in the modern (and original) dam structures were responsible for significant loss of water at the outlet of the lakes. Ground‐penetrating radar (GPR), electrical resistance tomography (ERT) and self‐potential (SP) surveys were collected at targeted sites and the information gained used to ascertain the nature of the observed/predicted lake water loss. The results show that both the modern and original dam appear to be intact, structurally sound and show no evidence for significant water flow through its structures. Instead, localized zones of natural, high‐density fracturing in the limestone bedrock appear to be the predominant cause of lake water loss.