Water and salt balance modelling to predict the effects of land‐use changes in forested catchments. 1. Small catchment water balance model

Abstract

A long-term water balance model has been developed to predict the hydrological effects of land-use change (especially forest clearing) in small experimental catchments in the south-west of Western Australia. This small catchment model has been used as the building block for the development of a large catchment-scale model, and has also formed the basis for a coupled water and salt balance model, developed to predict the changes in stream salinity resulting from land-use and climate change. The application of the coupled salt and water balance model to predict stream salinities in two small experimental catchments, and the application of the large catchment-scale model to predict changes in water yield in a medium-sized catchment that is being mined for bauxite, are presented in Parts 2 and 3, respectively, of this series of papers.The small catchment model has been designed as a simple, robust, conceptually based model of the basic daily water balance fluxes in forested catchments. The responses of the catchment to rainfall and pan evaporation are conceptualized in terms of three interdependent subsurface stores A, B and F. Store A depicts a near-stream perched aquifer system; B represents a deeper, permanent groundwater system; and F is an intermediate, unsaturated infiltration store. The responses of these stores are characterized by a set of constitutive relations which involves a number of conceptual parameters. These parameters are estimated by calibration by comparing observed and predicted runoff. The model has performed very well in simulations carried out on Salmon and Wights, two small experimental catchments in the Collie River basin in south-west Western Australia. The results from the application of the model to these small catchments are presented in this paper.

A conceptual model of daily water balance following partial clearing from forest to pasture

“…There was 4% bias between the observed and predicted streamflow. Similar monthly relationships were also obtained when the LAS-CAM model was applied at Wights and Salmon catchments (Sivapalan et al, 1996).…”

“…A distributed conceptual model, the Darling Range Catchment Model (DRCM), was developed and applied to some catchments in the Darling Range of Western Australia (Mauger, 1986). Sivapalan et al (1996) simplified the conceptual form of DRCM and developed the Large Scale Catchment Model (LASCAM). This model was tested, calibrated and validated across a range of different catchments, from small experimental to very large .…”

Ensemble modelling of nitrogen fluxes: data fusion for a Swedish meso-scale catchment

“…Lately, in the frame of assessing the impact of Land Use Change on Hydrology by Ensemble Modelling (LUCHEM; ) almost 30 different merging schemes were tested with 10 different model results over the same catchment as reported by Viney et al (2009). McIntyre et al (2005) also used model ensembles to predict discharge in ungauged or poorly gauged basin as part of the Predictions in Ungauged Basins (PUB; Sivapalan, 2003) initiative by the International Association of Hydrological Sciences. In the light of PUB, ensemble predictions are assumed to significantly increase the credibility of predictions.…”

Predicting effects of plantation expansion on streamflow regime for catchments in Australia

“…For example, if there is a large area of afforestation in catchments, will this affect water security or environmental flows during extended dry periods? A commonly used approach for predicting the impact of afforestation on streamflow is to rely on detailed physically based models (Baron et al, 1998;Legesse et al, 2003) or conceptual models derived from paired catchment studies (Sivapalan et al, 1996;Scott and Smith, 1997;Hundecha and Bárdossy, 2004). Use of physically based models in large catchments is problematic and impractical because of data requirements.…”