Hydrochemistry of Streams which enter St. Cuthbert's Swallet, Priddy, Somerset (UBSS Proceedings v.22(2))

Abstract: The current surface hydrology associated with St. Cuthbert's Swallet was studied between 1994 and 1997 by frequently sampling at 3 sites. The study period included spells of heavy rainfall in November 1994 and spring 1995 and a drought of historic proportions in 1995 when the Mineries Pool Outflow stream (the largest stream entering the cave) and a nearby spring stopped flowing. When flow of the Pool Outflow stream resumed, a huge surge of calcium sulphate appeared in its water. Most hydrochemical properties showed very low variability at Fair Lady Well. Periods of intensive sampling enabled the response of hydrochemical features to stream size to be investigated. Total, calcium and alkaline hardness varied inversely with stream size at the Pool outflow stream and at the main stream sink. Aggressiveness varied with stream size only at the Main Stream Sink. The mean concentration of nitrate in St. Cuthbert's Stream was below 4 × 10-5 M. Concentrations of potassium and nitrate showed seasonal variations except at Fair Lady Well. After the 1995 drought, the long delay before the Fair Lady Well flow restarted implies that the aquifer has an unknown lower point of discharge which had continued to flow after the well stopped flowing.