Abstract. This study evaluated the influence of
low-frequency oscillations, that are linked to large-scale
oceanographic–atmospheric processes, on streamflow variability in small
tropical coastal mountain rivers of the Sierra Nevada de Santa Marta,
Colombia. We used data from six rivers that had > 32 years of
complete, continuous monthly streamflow records. This investigation employed
spectral analyses to (1) explore temporal characteristics of streamflow
variability, (2) estimate the net contribution to the energy spectrum of
low-frequency oscillations to streamflow anomalies, and (3) analyze the
linkages between streamflow anomalies and large-scale, low-frequency
oceanographic–atmospheric processes. Wavelet analyses indicate that the
8–12-year component exhibited a quasi-stationary state, with a peak of
maximum power between 1985 and 2005. These oscillations were nearly in phase
in all rivers. Maximum power peaks occurred for the Palomino and Rancheria
rivers in 1985 and 1995, respectively. The wavelet spectrum highlights a
change in river variability patterns between 1995 and 2015, characterized by
a shift towards the low-frequency oscillations' domain (8–12 years). The net
contribution of these oscillations to the energy spectrum was as high as
51 %, a value much larger than previously thought for rivers in
northwestern South America. The simultaneous occurrence of hydrologic
oscillations, as well as the increase in the amplitude of the 8–12-year
band, defined periods of extremely anomalous wet seasons during 1989–1990,
1998–2002 and 2010–2011, reflecting the role of low-frequency oscillations
in modulating streamflow variability in these rivers. Cross-wavelet transform
and wavelet coherence revealed high common powers and significant coherences
in low-frequency bands (>96 months) between streamflow anomalies and
Atlantic Meridional Oscillation (AMO), Pacific Decadal Oscillation (PDO) and
the Tropical North Atlantic Index (TNA). These results show the role of
large-scale, low-frequency oceanographic–climate processes in modulating the
long-term hydrological variability of these rivers.
The role of catastrophic floods in shaping the morphology of river beds in small mountain catchment areas
