Surface waters and shallow groundwater samples were collected by completely filling 30 mL polyethylene bottles, which were then sealed with electrical tape to minimise the risk of evaporative loss. Rainwater samples were integrated samples of total monthly rainfall collected in a specially-adapted rainfall collector following IAEA protocols (IAEA http://www-naweb.iaea.org/napc/ih/documents/userupdate/sampling.pdf [accessed 22 June 2012). Stable isotopes of oxygen and hydrogen were determined simultaneously using a 'Picarro' WS-CRDS system at the University of Liverpool or the University of Cambridge. Jamaica, Parish of St Elizabeth. Wallywash Great Pond (lat: 17.9716°; long: -77.8068°) (lake water and groundwater samples) and Pon de Rock Guest House (lat: 17.9156°; long: -77.7973°) (rainwater samples). Refer to accompanying map for the precise location of the lake water sampling sites