The flood recession period in Western Amazonia and its variability during the 1985-2015 period

Study region: The upper Amazon River, where the water level measured at the Tamshiyacu station (Peru) shows seasonal variability of seven meters. Study focus: Key parameters for the flood recession period (beginning, end and duration of the low-water period, velocity of water falling and rising, and inversions in the direction of stage change known as "repiquete" events) are analyzed for the period 1985-2015, along with their relationship to rainfall integrated in the upper Amazon basin at Tamshiyacu. New hydrological insights: The low-water period lasts about four months, beginning, on average, at the end of July and ending in early November. Since the late 1990s, the low-water period has tended to end later, last longer and the flood recession ends more abruptly than it used to. This may be related to the increased frequency of dry days during the austral winter in the central and southern part of the basin and to increased and more intense rainfall in late spring (November-December). Repiquete events are frequent, 8 each year on average, and sometimes very acute: 18 events with a water-level reversal greater than one meter were registered during the 1985-2015 period. They are related to unusual, intense and extended rainfall during the week preceding the repiquete. Extensions of this preliminary work are suggested, as well as possible implications for recessional agriculture