Evaluation of the Application of the UDEP Methodology for the Desilting of Reservoirs to the Poechos Reservoir During the Coastal El Niño 2017

The Poechos reservoir is one of the most important hydraulic structures in northwestern Peru, with an initial capacity of 885 Hm3 and a current capacity of 397 Hm3. Its progressive sedimentation increased specifically during the extraordinarily humid years, 1983, 1998 and 2017, due to the high sediment load and the rules of operation, which are only oriented to guarantee the water supply for the different uses and flood control. The rules do not contemplate taking advantage of water energy for desilting, as recommended in specialized bibliography and in specific research for the Poechos reservoir, such as the UDEP methodology, developed in 2016 by the authors of this article (Reyes et al, 2018).

The methodology includes the forecast of the flows of entrance to the reservoir, the reliability of attention of the demand of the system and hydraulic measures, under guidelines obtained by numerical modeling. This procedure must be approved and adopted in the operation manuals of the structure to achieve gradual desilting using the water energy. The methodology was developed for Poechos as a pilot case.

An event coastal El Niño took place in 2017 at South America. It presented the ideal scenario for the application of the UDEP methodology. However, since it was not in the operations manuals, the operating entity could not apply it. The objective of this research is to demonstrate that with its application it could have carried out operations to clean the reservoir, taking advantage of the strength of the coastal El Niño.

This article evaluates the sedimentation produced during the period January-April 2017, through the flow of entry and exit and the bathymetries of the reservoir. In addition, the validation of the forecast model of the inflow flows is carried out. During the coastal El Niño 2017, this forecast would have allowed operating the reservoir under the UDEP methodology, updating with the flows that were presented in real time. The simulation of operation presented in this article shows that the predictions allow cleaning operations while ensuring the attention to the valleys irrigated by Poechos the rest of the year. In conclusion, if the operations manual had contemplated this methodology, it could have taken advantage of water energy, allowing a gradual and constant recovery of its usable volume.