Evaluation of streamflow complexity of two major Indian river basins using dynamic recurrence theoretical approach

This study presents dynamic application of recurrence quantification analysis (RQA) as an alternative approach for evaluation of streamflow complexity. Daily streamflows of 67 stations positioned in two major basins namely Mahanadi and Cauvery located at northern and southern India for 1980-2020 period are considered for recurrence analysis  (RA). Then a novel dynamic recurrence theory (DRT) approach is followed for evaluating the complexity of multiple streamflow segments along the time domain. The key recurrence measures such as Determinism, Laminarity, Entropy, Trapping Time along with mean diagonal length are quantified for multiple  segments along the temporal domain. The temporal evolution of recurrence measures showed abrupt alternations in complexity measures in majority of stations, except for 6 stations (16 %) of Mahanadi and 5 stations (17 %) of Cauvery, mostly falling within 1985-2000 period. The drastic shifts in complexity measures are coinciding more with the anthropogenic impacts than climatic drivers. The streamflow dynamics of  Cauvery basin is found to be more erratic and complex than that of Mahanadi basin. In general, the streamflow dynamics of stations located in lower reaches are more complex and controlled by flow regulations than that of the upper reaches of both the basins. The insights gained from the novel DTA approach are noted to be helpful in identifying the prominent changes in streamflow and hence giving better insights on to its predictability.