Complexity analysis of riverflow time series

I have used the Lempel–Ziv measure to assess the complexity in riverflow activity over England and Wales for the period 1867–2002. In particular, I have examined the reconstructed monthly riverflow time series from fifteen representative catchments in these regions and calculated the Lempel–Ziv Complexity (LZC) value for each time series. The results indicate that the LZC values in some catchments are close to each other while in others they differ significantly. In addition, I have divided the period 1867–2002 into four equal subintervals: (a) 1867–1900, (b) 1901–1934, (c) 1935–1968, (d) 1969–2002, and calculated the LZC values for the various time series in these subintervals. It is found that during the period 1969–2002, there is a decrease in complexity in most of the catchments in comparison to the subinterval 1935–1968. This complexity loss may be attributed to increased human intervention involving land and crop use, urbanization, commercial navigation and climatic changes due to human activity. Determining the complexity in the riverflow time series is important because an understanding of the extent of complexity may be useful in developing appropriate models of riverflow activity. The extent of complexity may also influence the predictability of the variability in riverflow dynamics.