Disaggregation of Streamflow Volumes

A disaggregation model, which differs from those developed by Valencia and Schaake (VS) and Mejia and Rousselle (MR) (referred to as the HB model), was developed specifically to preserve correlations between seasons joining water years in addition to the properties preserved by the basic VS model. The HB model simultaneously disaggregates two consecutive annual flow volumes, then the next two, etc. The HB model is extended to be able to disaggregate skewed seasonal flows that follow three-parameter log-normal distributions (3PLN). Mixtures of skewed and nonskewed seasonal flow volumes are approximated by 3PLN distributions for operational convenience. Practical considerations concerning use of these models for multisite flow disaggregation are reviewed together with computational space requirements and limitations on model computability. A HB 3PLN model for single-site flow disaggregation is used in an example application where comparisons are made with the MR model.