Assessment of reservoir sedimentation and mitigation measures: A case study of Palo Redondo reservoir

The accelerated sedimentation of the main Peruvian reservoirs has caused losses of the useful storage capacity that significantly affects the water allocation to the different users. This research aims to evaluate the sedimentation risk of Palo Redondo Reservoir of the Chavimochic hydraulic system, located in La Libertad region of Peru's northern, proposing alternatives to reduce its impacts. The reservoir was designed for a total capacity of 400 MCM, however, it is likely that in the future it has an accelerated sedimentation problem due to the high erosion of the Santa River Basin and because of its water uptake system whose sand trap has an efficiency less than 75%. The methodology includes the modeling for the prediction of stream flow and sediment yield in the Tablachaca sub-basin which is a critical drainage area of the Santa River Basin, using the soil and water assessment tool (SWAT). Likewise, it includes the modeling of sediment yield in the Palo Redondo small sub-basin using the kinematic runoff and erosion model (KINEROS). It could be activated during the occurrence of the El Niño phenomenon causing maximum discharges with high rates of sediment transport to the reservoir. The SWAT calibration results show a good model performance with NASH coefficients greater than 0.6 for flow rates and sediment concentrations, respectively. On the other hand, the land cover change in Tablachaca sub-basin shows a significant reduction in erosion rates and, therefore, a significant reduction of sediments towards the Palo Redondo Reservoir.