“…The algorithms used to find the “optimal” parameters may range from simple search algorithms that seek iterative improvement of the objective function starting from a single location in the search space [e.g., Ritter et al , 2003] to more advanced global search methods that utilize the strength of a population of individuals to efficiently search the space of potential solutions and avoid getting stuck in a local minimum of the objective function. Global optimization methods that have been used for the estimation of the unsaturated soil hydraulic properties include the annealing‐simplex method [ Pan and Wu , 1998], genetic algorithms [ Takeshita , 1999], multilevel grid sampling strategies [ Abbaspour et al , 2001; Lambot et al , 2002], ant colony optimization [ Abbaspour et al , 2001], and shuffled complex methods [ Vrugt and Bouten , 2002; Mertens et al , 2004, 2005, 2006]. Recent extensions include multiobjective search methods [e.g., Vrugt et al , 2003; Vrugt and Dane , 2005; Mertens et al , 2006], and simultaneous multimethod genetically adaptive optimization algorithms [ Vrugt and Robinson , 2007; Wöhling et al , 2008].…”