Characterising Rhythmic and Episodic Pulsing Behaviour in the Castleton Karst, Derbyshire (UK), Using High Resolution in-Cave Monitoring

The discharge from most karst springs exhibits a consistent and reasonably predictable response to recharge but a few exhibit short-term ('rhythmic') changes in flow that are commonly attributed to the geometry of feeder conduits and the action of siphons. This paper investigates water flow in a karst system that exhibits rhythmic and episodic changes in discharge due to variations in flow from two phreatic conduits (Main Rising (MR) and Whirlpool Rising (WR)) that pass through Speedwell Cavern en route to the springs. Water tracing experiments indicate that the conduits receive both allogenic and autogenic recharge. Flow dynamics and conduit behaviour were investigated using high-resolution (2-min) water depth data collected from MR and WR between 2012 and 2015 (when MR was dominant) and between 2021 and 2023 (when WR was dominant). Water depths were also logged in a cave at the upstream end of a conduit draining to both MR and WR and at springs. The short-term temporal variability in water depths at both MR and WR is greater than any documented in previous studies. This is attributed to conduit bedrock geometry and changes in conduit permeability due to sediment accumulation in phreatic loops, which together influence the response to recharge.

Automated summary

This study investigates a karst system that exhibits rhythmic and episodic changes in discharge due to variations in flow from two phreatic conduits. Water tracing experiments reveal that the conduits receive both allogenic and autogenic recharge. High-resolution water depth data collected from the conduits and upstream cave during different periods show that the short-term temporal variability in water depths is influenced by conduit bedrock geometry and changes in conduit permeability caused by sediment accumulation in phreatic loops.