This paper presents a case study to illustrate the use of daily transient water balance calculations to inform the conceptual understanding of the hydrogeology of a limestone catchment. The hydrogeology of karstic systems is often considered to be too complex to be amenable to any useful degree of quantification. However, this example shows that, where there are good time series of inflow (e.g. rainfall) and outflow (e.g. spring flows), transient water balance calculations (which simplify the groundwater system to a series of 1D ‘stores’) can make a useful contribution to the conceptual understanding of these groundwater systems and may allow an assessment of future impacts to be made. These calculations can also help in the design of appropriate mitigation measures.