The impact of a changing climate on the Amazon basin is a subject
of intensive research because of its rich biodiversity and the significant role of
rainforests in carbon cycling. Climate change has also a direct hydrological impact,
and increasing efforts have focused on understanding the hydrological dynamics at
continental and subregional scales, such as the western Amazon. New projections
from the Coupled Model Inter-comparison Project Phase 5 (CMIP5) ensemble indicate
consistent climatic warming and increasing seasonality of precipitation in the Peruvian
Amazon basin. Here we use a distributed land surface model to quantify the potential
impact of this change in the climate on the hydrological regime of the upper Amazon
river. Using extreme value analysis, historical and future projections of the annual
minimum, mean, and maximum river flows are produced for a range of return periods
between 1 and 100 years. We show that the RCP 4.5 and 8.5 scenarios of climate
change project an increased severity of the wet season flood pulse (7.5% and 12%
increases respectively for the 100-year return floods). These findings agree with
previously projected increases in high extremes under the Special Report on Emissions
Scenarios climate projections, and are important to highlight due to the potential
consequences on reproductive processes of in-stream species, swamp forest ecology,
and socio-economy in the floodplain, amidst a growing literature that more strongly
emphasises future droughts and their impact on the viability of the rainforest system
over greater Amazonia