Development of a salt and water balance model for a large partially cleared catchment

Abstract

A salt and water balance model was developed to represent stream flow and salinity generation processes following land use changes. At first a fundamental building-block model was developed based on the ‘downward approach’. The building-block model was tested and validated with data from six experimental sub-catchments within the Collie River basin in Western Australia. The approach requires specification of five physically meaningful key parameters, most of which can be obtained a priori or easily calibrated.

Streamflow and salinity from the Collie River catchment, with an area of2,545 km², has increased significantly due to clearing of 26% of the area during 1940–70s. For this study the catchment was divided into 91 sub-catchments and the building-block model was applied to each of the sub-catchments. Most of the known catchment attributes such as stream length, average slope, soil type, profile thickness and salt storage were incorporated into the model. Parameter values obtained from experimental sub-catchments were appropriate for representing the daily streamflow generation processes of the whole catchment. However, the prediction of stream salinity and salt loads was improved by running the model a number of times and taking the final values of the transient stream zone stores as an initial condition. The modelled daily stream flow, salinity and salt load hydrographs matched very well for all gauged sub-catchments.

Keywords:

• Collie River
• Land use change
• Stream flow
• Salinity
• Catchment model

Additional information

Notes on contributors

M. A. Bari

Mohammed Bari is a Senior Engineer at the Water and Rivers Commission, Western Australia. He holds a Master of Engineering degree in Water Resources. His areas of interests are catchment and lake hydrology, with a particular emphasis on the role of landscape changes on stream flow and salinity. He has a strong interest in the development and application of different types of catchment hydrology models. He is currently completing a (part-time) Doctor of Philosophy degree at the University of Western Australia.

K.R.J. Smettem

Keith Smettem is an Associate Professor at Centre for Water Research, the University of Western Australia. His areas of interest include the theory and measurement of water and chemical movement through soils and landscapes and the development of indirect methods for parameterising water balance and hydrologic models.