Rising groundwater levels and increasing salinity concentrations within Mona Park, a tropical conjunctive water use irrigation district, is causing concern for farmers and regional water managers. In this paper we describe results of a study aimed at improving understanding of the linkages between historical developments and trends in groundwater. We highlight in particular the rapid and large response in groundwater during a wet period in 2000 which we believe reflects a change in behaviour from an unconfined aquifer to that of a semi-confined or confined aquifer. We also discuss changes in groundwater salinity and highlight the need to understand the spatial and temporal dynamics in the system. The aim of the work is to help land and water managers explore alternative management practices that reverse current trends and maintain improved water table conditions in terms of both water quantity and quality.