Using WEC-C, a distributed, deterministic catchment model, to simulate hydrologic responses to agricultural clearing

The water and environmental consultants — catchment model is a distributed, deterministic, catchment-scale water flow and solute transport model specifically developed to assess the effects of land uses such as agricultural clearing, forest logging and surface mining on the stream flows and salinities of a catchment. This paper describes its application to Lemon catchment, a small catchment in the low rainfall zone of the Darling Range of Western Australia, which had half its area cleared for agriculture. Specific parameterisation to Lemon catchment was not the aim; rather a parameter set consistent with our present understanding of the behaviour of Darling Range catchments and with the available hydrological data for the catchment. The resultant model was termed a mimic by the authors in that its appearance and behaviour are similar to the original in a way that satisfies the observer, but due to the known limitations of distributed, deterministic models it, like all such models, cannot be considered a true construct of the catchment. It was noted however that this particular model did appear to accurately mimic the catchment’s hydrology and that this was achieved while: extensively using published and measured field data to parameterise the model; using fewer calibrated parameters than comparable models; and successfully matching history to groundwater level and stream flow, salinity and salt load data. The authors believe that a workable methodology for the application of distributed, deterministic models was presented and that the utility of these models was placed into correct perspective.