Sustainable Sediment Management, Yaku HPP, Peru

Client: EnerSur, Lima, Peru

Contract Period: 2014-2015

The proposed 258 MW (254 m3/s) Yaku hydropower project is located on Río Marañon, Peru, in the lower Andes within the Amazon watershed. It is being designed as a run-of-river project with daily regulation, using a 120 m tall dam to provide 115 m of gross head. However, with a suspended sediment load of 13 M t/yr, the 280 Mm3 reservoir is expected to completely fill with sediment within about 30 years. Therefore, the initial project design will incorporate the sediment management measures required for long-term sustainable operation.

We were contracted as owner’s consultant to assist in the development of the sediment management strategy for this project, focusing on the following issues:

  • Review of hydrology and the limited suspended sediment data, and provide recommendations to improve suspended sediment data collection.
  • Estimate suspended and bed load transport.
  • Review all potentially feasible sediment management options and recommend a strategy that insures long-term operation while maximizing power production.
  • Specification and expert review of all modeling investigations.
  • Provide guidance on dam and intake design and development of operational rules, to meet the project’s sediment management objectives.

To date we have outlined the preferred sediment management strategy to consist of empty flushing, and there is also the potential to release turbidity currents. We have provided detailed recommendations to improve sediment monitoring, as there is very limited data at high discharges, and have provided initial recommendations concerning the placement of flushing outlets, the probable operating rule, and the feasibility of using a bypass tunnel.

If sediment flushing is selected as the sole sediment management measure, the reservoir will initially act as a sediment trap until some future time when sufficient sediment has collected to initiate flushing operations to achieve a balance between sediment inflow and outflow while maintaining the pondage volume for daily regulation plus volume needed for sediment trapping to avoid construction of a desander. If turbid density currents are released during the initial years of operation, this could significantly delay empty flushing and increase power production during this delay period.