This assessment tool is designed as a planning aid to help farmers evaluate the potential usefulness of small farm dams and, in particular, their performance under dry conditions. It is not intended to replace professional hydrological assessment or engineering advice.
The model operates on a set of generalised assumptions about dam behaviour, catchment characteristics, and water demand. Calibration of loss factors, including seepage and runoff efficiency, is an ongoing process, and as a result the model may show heightened sensitivity to rainfall inputs in some scenarios. Users should treat outputs as indicative rather than definitive, particularly where rainfall-driven runoff is the dominant factor.
The tool is most reliable where it matters most: extended dry periods. Under drought conditions, precisely when water security is critical and farmers most need to understand whether a dam can sustain their needs, the model's behaviour is primarily governed by evaporation rather than runoff. The evaporation component becomes more dominant and is better calibrated than the rainfall-runoff component, giving greater confidence in outputs during dry spells.. The tool also performs well at the wet end of the spectrum, and in both cases can help answer the practical question of how long a dam is likely to last under a given set of conditions.
The underlying model is subject to ongoing development. We are actively building knowledge from monitored study sites, and future refinements will improve accuracy across a broader range of conditions.
Users are encouraged to use this tool as a starting point for planning conversations rather than a basis for final decisions.