On the relationship between reversal of the river stage (repiquetes), rainfall and low-level wind regimes over the western Amazon basin

Manuel Figueroa,Elisa Armijos,Jhan Carlo Espinoza,Josyane Ronchail,Pascal Fraizy

doi:10.1016/j.ejrh.2020.100752

Abstract

Study regionThe Amazonas River and its tributaries (Peru), where riparian farmers face hydrological events that put their lowland crops at high risk of production loss during the flood recession period. Study focusThis paper analyzes the hydro-meteorological mechanisms over the Andes-Amazon basins that produce “repiquetes”, which are sudden reversals of the river stage. They are defined and characterized for the period 1996–2018 by using river stage data from three hydrological gauging stations for the Amazonas, Marañón and Ucayali Rivers. Daily rainfall and low-level winds depict the large-scale atmospheric patterns associated with repiquetes. New hydrological insightsAmong 73 significant repiquetes (reversal ≥ 20 cm) observed in the Amazonas River, 64 % were preceded by repiquetes only in the Marañón River, 5 % by repiquetes only in the Ucayali River, 21 % by repiquetes in both rivers and 10 % was only registered in the Amazonas River without upstream precursor. These results show that repiquetes in the Marañón River are the primary precursors of repiquetes in the Amazonas River. Most repiquetes are associated with abundant rainfall over the Peruvian and Ecuadorian Andes-Amazon transition region related to a remarkable change in the direction of the meridional wind, from north to south, and an easterly flow five to three days before the beginning of a repiquete in the Amazonas River.

Highlights

Most of the Andean rivers within the Amazon basin of Peru and Ecuador flow into the Amazonas River, which is formed by the confluence of the Ucayali and Maranon Rivers
We identify four types of repiquetes: Type 1, Type 2, Type 3 and Type 4
Within the common period analyzed for the three rivers, and considering as significant only those repiquetes that exceed the thresholds of 20 cm in Tamshiyacu and 10 cm in San Regis and Requena stations, only 73, 117 and 85 repiquetes are found in Tamshiyacu, San Regis and Requena stations, respectively

Summary

Introduction

Most of the Andean rivers within the Amazon basin of Peru and Ecuador flow into the Amazonas River, which is formed by the confluence of the Ucayali and Maranon Rivers. Downstream the confluence of the Ucayali and Maranon Rivers and near to the city of Iquitos, riparian communities practice riverine agriculture. They take advantage of the falling water level of the flooding cycle to cultivate in the exposed riverbed, flood plains and point bars during annual recession (Hiraoka, 1985; Rios Arevalo, 2005; Coomes et al, 2016; List, 2016; List and Coomes, 2017; Ronchail et al, 2018) since the soils are enriched by sediment transport from the Andes (McClain and Naiman, 2008). Ronchail et al (2018) found evidence of a lengthening of the low water period since the eighties and linked repiquetes events to unusually high rainfall over the Tamshiyacu basin during the week leading up to these events in Tamshiyacu

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