Comparative assessment of three approaches for deriving stream power plots along long profiles in the upper Hunter River catchment, New South Wales, Australia Vikrant Jain a, * , Nicholas Preston b , Kirstie Fryirs a , Gary Brierley c a Department of Physical Geography, Macquarie University, North Ryde, NSW 2109, Australia b School of Earth Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand c School of Geography and Environmental Science, The University of Auckland, P.O. Box 92019, Auckland, New Zealand Received 6 April 2005; received in revised form 26 August 2005; accepted 29 August 2005 Available online 21 October 2005 Abstract The downstream distribution of stream power is derived and analysed for 11 different streams in the upper Hunter River catchment, Australia. Stream long profiles were produced in a GIS environment using DEM data and catchment area–discharge analysis. These profiles were analysed using three approaches, namely long profile smoothing, curve fitting and a theoretical model. The methodology for deriving stream power profiles using these three approaches is discussed. The long profile smoothing method provides a good approximation of the subcatchment variability in stream power trends. The curve fitting method shows that higher-order exponential curves provide a better fit for long profile data. For the streams of the upper Hunter River catchment, second-order exponential curves fit well with significantly less error. The curve fitting method predicts a bimodal (upstream and midstream) distribution of stream power, which is a deviation from our earlier understanding of a single midstream peak. The theoretical approach provides a mathematical expression of the observed bimodal stream power distribution. The bimodal distribution emphasises the erosion potential of headwater reaches. The resultant stream power distribution provides a catch- ment-scale characterisation of the distribution of available energy in any given system. Using these approaches, the variability of stream power in headwater reaches is explained by discharge variability, while variability in midstream and downstream reaches is related to high variability in channel gradient. D 2005 Elsevier B.V. All rights reserved. Keywords: Stream power; Energy distribution; DEM; Long profile; New South Wales (NSW) 1. Introduction Channel appearance and behaviour are governed by the balance between driving and resisting forces. The rate of doing geomorphic work by stream water, com- monly expressed as stream power, provides a measure of the driving force. The stream power of descending water is defined as the rate of energy conversion from potential to kinetic form (Bagnold, 1966). Considering the importance of the role of stream power in the functioning of fluvial systems, attempts have been made to determine the distribution of stream power either through point-location studies (e.g., Magilligan, 1992; Lecce, 1997; Fonstad, 2003) or through contin- uous distributions of stream power based on stream long profiles (e.g., Knighton, 1999; Finlayson et al., 2002; Fonstad, 2003; Reinfelds et al., 2004). 0169-555X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2005.08.012 * Corresponding author. Tel.: +61 2 98508318; fax: +61 2 98508420. E-mail address: vjain@els.mq.edu.au (V. Jain). Geomorphology 74 (2006) 297 – 317 www.elsevier.com/locate/geomorph