Estimating shallow groundwater recharge in the headwaters of the Liverpool Plains using SWAT

A physically based catchment model (SWAT) was used for recharge estimation in the headwaters of the Liverpool Plains in NSW, Australia. The study used water balance modelling at the catchment scale to derive parameters for long-term recharge estimation. The derived parameters were further assessed at a subcatchment scale. Modelling results suggest that recharge occurs only in wet years, and is dominated by a few significant years or periods. The results were matched by independently observed bore data across the study area in the past 30 years. The study suggests that variations in recharge can be primarily explained by the climatic factor rather than land-use changes. The study estimated less recharge than previous studies where point scale modelling results have been scaled up to the catchment scale. It suggests that a catchment-based approach is needed for recharge estimation at the catchment scale. The study indicates that the current model may overestimate runoff on cracking vertosols under dry conditions where improvement is likely needed. The need for long-term runoff and bore monitoring data to confidently establish the relationships among water balance/recharge estimation and groundwater level variation is discussed. SWAT provides an alternative to point scale modelling for evaluating recharge and its response to changes in land use and land management.