Non-linearities in drip water hydrology: an example from Stump Cross Caverns, Yorkshire

Drip rate data have been collected at 15 min intervals at six locations in Stump Cross Caverns, N England, since 1998. The different drip sites cover a wide range of drip rates from ~2 drips/s to 2 drips/h, and in general the variability of drip rate increases with mean drip rate. In our continuous data sampling we observe rapid discharge increases which appear to be synchronous between drips sites, and which can be explained by flow switching of the water overlying the cave during times of high infiltration rate, such as intense rain storms or rapid snowmelt. A test for non-linearity (White test) in the drip series provides very strong evidence that many of the drip sequences are non-linear. We conclude that at our drip sites there is a non-linear input (weather) and non-linearities within the karst system leading to non-linear dripping, which is independent of drip rate. Our results have implications for stalagmite palaeoclimatology, where such widespread non linearities have not been taken account of.