Nonlinear Processes in Geophysics www.nonlin-processes-geophys.net 1023-5809 1607-7946 12 4 2005 10.5194/npg-12-461-2005 http://www.nonlin-processes-geophys.net/12/461/2005/ http://www.nonlin-processes-geophys.net/12/461/2005/npg-12-461-2005.html http://www.nonlin-processes-geophys.net/12/461/2005/npg-12-461-2005.pdf 461 469 2005-05-03 Streamflow dynamics at the Puget Sound, Washington: application of a surrogate data method N. She D. Basketfield Seattle Public Utilities, City of Seattle, 700 5th Ave., Suite 4900, PO Box 34018, Seattle, WA 98124-4018, USA Recent progress in nonlinear dynamic theory has inspired hydrologists to apply innovative nonlinear time series techniques to the analysis of streamflow data. However, regardless of the method employed to analyze streamflow data, the first step should be the identification of underlying dynamics using one or more methods that could distinguish between linear and nonlinear, deterministic and stochastic processes from data itself. In recent years a statistically rigorous framework to test whether or not the examined time series is generated by a Gaussian (linear) process undergoing a possibly nonlinear static transform is provided by the method of surrogate data. The surrogate data, generated to represent the null hypothesis, are compared to the original data under a nonlinear discriminating statistic in order to reject or approve the null hypothesis. In recognition of this tendency, the method of "surrogate data" is applied herein to determine the underlying linear stochastic or nonlinear deterministic nature of daily streamflow data observed from the central basin of Puget Sound, and as applicable, distinguish between the static or dynamic nonlinearity of the data in question.