A variable-length block bootstrap method for multi-site synthetic streamflow generation

The complexity of stochastic streamflow generators limits their practical use, highlighting the need for effective but simpler approaches. An attempt to meet this objective is presented using variable-length bootstrapping (VLB) of annual flows, and a weighted method of fragments for disaggregation and perturbing the bootstrapped annual flows. The perturbations enable generation of annual flows different from those present in the historical record, thereby overcoming one of the main limitations of the classical bootstrap method. The VLB replicates adequately nine historical annual statistics of a five-site problem, and reproduces the annual serial and cross-correlations better than STOMSAa state-of-the-art parametric generator. The VLB achieves reasonable validation using the sum of minimum flows and the reservoir storage size test. Because of the modification of the monthly flow distribution caused by the weighted averaging of fragments, the VLB cannot be safely used for within-year analysis, but is a potentially robust annual streamflow generator. Citation Ndiritu, J. (2011) A variable length block bootstrap for multi-site synthetic streamflow generation. Hydrol. Sci. J. 56(3), 362-379.