A suite of core-scale

permeability tests reveal permeabilities between 3 × 10−18 and 6 × 10−13 m2 for samples of lava and volcaniclastic deposits. Generally, coarser and less altered samples demonstrate higher permeabilities (>10−14 m2), while cores with finer and altered matrix material exhibit permeabilities below 10−15 m2. Andesitic lava samples also reveal low permeabilities, on the order of 10−16 m2. Analysis of a previous pumping test on a confined aquifer in Montserrat’s Belham valley reveal Angiogenesis inhibitor aquifer permeability of 10−10 m2. New insights and observations from Montserrat combined with a review of existing understanding of hydrologic on volcanic islands provides the basis for a discussion on potential conceptual hydrological models for Montserrat, specifically the Centre Hills springs. Current observations from Montserrat are consistent with two possible conceptual

hydrological models for volcanic island settings. Type 1 resembles the model applied to the Canary find more Islands; a low permeability core within the interior of the island elevates the water table allowing the development of aquifers and springs at high elevation. Type 2 is based on a conceptual model devised for Hawaii; springs are supplied by perched aquifers above low permeability, weathered aquitard. The hydrology of Montserrat is further complicated by the active volcanic system in the south. This link is not restricted to fumaroles on the flanks of the active SHV; high temperature, low elevation springs at Hot Water Pond suggest that volcanic influence on the hydrology extends to the east coast, some 6 km from the active vent. Elevated temperatures and SEC in the southern springs on CH point towards a contribution from warmer waters potentially supplied through

faults from a warmer aquifer at depth. The insights presented here provide useful constraints for numerical simulations to explore the fundamental hydrology of Montserrat, and distinguish which of these two conceptual models best represents Montserrat’s hydrological Venetoclax mouse system and the hydrology of volcanic arc islands in general. Improving our understanding of fundamental hydrology of such islands is essential for exploring hydrological and volcanic interactions as well as assessing the behaviour of a vital resource in response to a changing climate. None declared. The authors would like to thank MUL, Montserrat for providing access to their data archive and assistance in the field. In particular, this work was made possible by invaluable field support and guidance from Reuel Lee and Bill Tonge (formerly MUL). We are also grateful for assistance and contributions from a number of MVO staff and for assistance in the field from Alia Jasim (UOB). Thanks also to Jenni Barclay and Adrian Matthew for sharing rainfall data, and Steve Sparks for allowing access to CALIPSO cores. This work is funded by the NERC BUFI programme (studentship no.