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In-Young Yeo, Steven I. Gordon, and Jean-Michel Guldmann

-land-use optimization model. The impacts of on-site land-use changes are evaluated with a process-based runoff simulation model within the framework of a land-use optimization algorithm. This algorithm is based on the standard principles of nonlinear programming, using the gradient as direction of steepest ascent, and leads to local optima. However, because the objective function cannot be expressed in closed mathematical forms, its derivatives are numerically approximated by using the simulation model. This model

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Martin-Pierre Lavigne, Alain N. Rousseau, Richard Turcotte, Anne-Marie Laroche, Jean-Pierre Fortin, and Jean-Pierre Villeneuve

al., 2003 ; Fortin et al., 1995 ; Fortin et al., 2001a ; Fortin et al., 2001b ). HYDROTEL, a semidistributed physically based model, integrates six computational modules that are run in a cascade (i.e., in a decoupled manner): weather data interpolation, snow cover dynamic, potential evapotranspiration, soil moisture balance, surface runoff, and streamflow. Each module offers more than one computational algorithm based on the availability of data for the studied watershed. Some algorithms

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Ademola K. Braimoh and Paul L. G. Vlek

difference vegetation index (NDVI) as a measure of biomass over the landscape; the tasseled cap transform to produce orthogonal soil, vegetation, and water-related bands; and principal component analysis to reduce data redundancy. The first two principal components were combined with NDVI and tasseled cap bands to generate a six-band image for training signature development and classification. Ground truth data for image classification using supervised maximum likelihood algorithms were obtained from the

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Christopher Potter, Pusheng Zhang, Steven Klooster, Vanessa Genovese, Shashi Shekhar, and Vipin Kumar

, 1999 ). These estimated PET methods have been validated in numerous different climate zones ( Potter et al., 2001 ; Federer et al., 1996 ). The complete algorithm we have used is actually equivalent to PREC − ET because the minimum allowed value of the difference is zero (i.e., there can be no ET greater than the available PREC). 3.4. Climate indices The influence of ocean surface climate events, such as ENSO, on atmospheric circulation and land surface climate have been noted as a significant

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Ademola K. Braimoh and Paul L. G. Vlek

on 5 November 1984, 21 December 1992, and 7 November 1999 were used. The images were georeferenced to Universal Transverse Mercator (UTM) projection, with the root-mean-square error below pixel size. Radiance values for 1984 and 1992 images were normalized to the 1999 image following Hall et al. ( Hall et al., 1991 ). Land-cover classification was performed using the maximum likelihood algorithm. Six classes were discriminated: closed woodland, open woodland, grassland, cropland, built-up area

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