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Abstracts for papers on Wetness Index Computation

O'LOUGHLIN, E.M., SHORT, D.L. and DAWES, W.R. (1989): Modelling the hydrological response of catchments to landuse change. In: Proceedings of the 1989 Australian Institution of Engineers Hydrology and Water Resources Symposium. Nat. Conf. Publ., No. 89/19, pp. 335-340.

A distributed parameter hydrologic model, based on analysis of topography in re-distributing soil moisture in natural terrain is described. The model, TOPOG, can be adapted to predicting the hydrologic impact of land-use change, by simulating the effects of locally altered water balance. Example applications include dry and wet weather simulations of moisture status in catchments, the size and locations of non-point source areas of particulate runoff, effluent disposal using absorption trenches, and rehabilitation of salinised land.

NANDAKUMAR, N., LANE, P.N.J., VERTESSY, R.A. and O'LOUGHLIN, E.M. (1994): Prediction of soil moisture variability using wetness indices. In: Water Down Under 94: Proceedings of the Australian Institution of Engineers Hydrology and Water Resources Symposium, Adelaide, 21-25 November, 1994, Volume 3, pp. 49-54.

Lateral water movement in a hillslope depends on topographical and pedological attributes. Due to spatial variation of these attributes and temporal variation of climatic variables such as rainfall and evaporation, soil moisture changes both in time and space. A number of steady-state wetness indices have been formulated to account for the influence of topographical attributes on catchment moisture status. This paper presents an application of a steady-state wetness index concept to predict the spatial variability of soil moisture at an experimental catchment. In addition, a transient contributing area concept explains the discrepancy between steady-state wetness index predictions and soil moisture measurements. An equation for transient wetness index has been derived by introducing transient subsurface flow and evaporation in the original nondimensional wetness index equation. The transient wetness index significantly improves the predictions of both spatial and temporal variability of soil moisture. The limitations of these indices are discussed.