Wavelet analysis of discharge and sediment load for the Subarnarekha, Brahmani, and Mahanadi rivers of India

This study aims to identify distinct small-scale temporary patterns between the river discharge and suspended sediment load for the main tropical rivers using continuous wavelet transform. Strong annual and irregular semi-annual variabilities, with few quarterly and interdecadal variabilities, are observed in river discharge and sediment load. The wavelet coherence reveals that the strongest in-phase coherence relationships exist between total suspended sediment and streamflow. The methodology for identifying the primary climate factors that integrate the partial wavelet coherence (PWC), multiple wavelet coherence (MWC), and quadruple wavelet coherence (QMWC) techniques is presented. The results show that the El-Nino/Southern Oscillation (ENSO) is the major regulator of streamflow followed by Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). The chosen rivers show a statistically significant ($p \le 0.05$p <= 0.05) descending trend in sediment load but no significant positive or negative trend in river discharge. This could be due to regional sediment storage and large-scale stream events affecting the sediment transport dynamics.