120-year records of spring flows in the Pentland Hills, geological controls and response to drought

An archive of hand written operations logs from the former Edinburgh Water Works allows a largely complete record of spring flows to be examined for the 120-year period beginning 1862. The two longest and most consistent records in the archive are for Black Springs, draining an area of talus formed on microgranite and Silurian sediments, and the Bavelaw Springs, which drain the Carboniferous Kinnesswood Formation comprised mostly of sandstones. Weekly flow records are available from 1904, while the 1862–1903 period has monthly data in published form. Auto- Regressive Moving Average Analysis (ARIMA) was used to model the key parameters of the time series. The Black Springs showed a marked variability in flows, indicative of a strong quickflow response superimposed on a baseflow. By contrast, the Bavelaw Springs were much more heavily damped in their response, exhibiting lower within-year and inter-year variability. Recessionary flows were extracted from each record for analysis and comparisons. Results showed consistency in the extended Bavelaw recessions, while those from the Black Springs showed greater variability. The characteristic response of the spring groups will be instructive for water resources modelling and for assessing the effects of climate change on groundwater reserves. Groundwater time series from Scotland’s only index well begin only in 1981, while just six in England date back to the 19th century, illustrating the relative paucity of long groundwater records.