2.1.4. Sediment Concentration

Pastaza River is the third-largest river in Ecuador with an average annual flow 144.4 m3/s and a precipitation of 3255 mm. Sediment concentration was determined based on data from San Francisco hydropower plant. The samples were collected daily 1 km upstream of the reservoir, in the reservoir itself, in the desilting chamber, and at the discharge during a month, as shown in Figure 2. Since heavier particles tend to deposit on the reservoir bed and mostly only suspended particles are drawn by the intake, water samples were taken at a constant depth of about 2 m from the surface. The average concentration was estimated considering daily values from all sampling points throughout the sampling period.

**Figure 2.** Sediment concentration in July 2010.
