“…ARMA(p, q) models have been extended to describe seasonal flow series by having their coefficients depend upon the season-these are called periodic Autoregressive-Moving average models, or PARMA. Salas and Obeysekera (1992), Salas and Fernandez (1993), and Claps et al (1993) discuss the conceptual basis of such stochastic streamflow models. For example, Salas and Obeysekera (1992) found that low-order PARMA models, such as a PARMA(2,1), arise from reasonable conceptual representations of persistence in rainfall, runoff, and groundwater recharge and release.…”