RC15 - Puente Vilca

Site Code: RC15. GPS: S12°12978, W75°818722. Elevation: 3822m asl.

Water Quality Data

The following river and water quality data was collected from this site:

RC15 November 2019 November 2021
Season: Austral Summer Austral Summer
Date: 22.11.2019 21.11.21
Time: 9.00am 11.00
Width (m) 27.0 27.0
Depth (Av.) (m) 0.58 0.58
CSA (Av.) (m²) 15.66 15.67
Velocity (Av.) (m/s) 1.45 1.46
Discharge (Av.) (m³/s) 22.754 22.770
Riverbed sediment Gravel, cobbles & small boulders Mainly cobbles
Temp. (Atmospheric) (°C) 11 11
Temp. (Water) (°C) 11.43 11.97
Atmospheric pressure (mbar) 678  
Dissolved oxygen (mg/l) 3.56 5.42
Dissolved oxygen (%) 50.50 78.25
pH 8.45 8.21
Conductivity (µS/cm) 410 528
Total Dissolved Solids (ppm) 205 264
ORP (mV) 126.2 66.5
Turbidity Clear: Clear:
Alkalinity (mg/l CaCO₃) - 165 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) - -

Data Analysis

Discharge at this point along the Rio Canete is very high at over 22 m³/s. The fluctuations in discharge throughout the catchment reflect localised abstraction. However, the difference between RC15 and RC14 must mean that considerable amounts of water pass through subterranean channels and groundwater flows.

At almost 3800m asl the DO readings at RC15 fall within the range to be expected. It again follows the pattern in which DO readings slowly fall as elevation increases. The measurements for conductivity and total solids are fairly high, which probably reflects local geological conditions and weathering processes in the river channel, but this is yet to be determined. At these levels of conductivity and total solids, water quality is not poor. As the population density above Puente Vilca is very low, the impact of anthropic activity is minimal. There is some pastoral agriculture associated with the village of Tanta. However, this is very distant from this site and lies above the large Pucaracocha (upper El Platanal) reservoir.

Site Descriptions

Site RC15 lies in the arid temperate zone well above the town of Huancaya at 3877m asl. At this point the valley has a U-shaped profile and is shallower. This reflects the fact that we are reaching the headwaters and clearly glaciated landscapes. The channel gradient is also broken by a series of lakes, marshy areas and bofedales. The bed load in the river channel is comprised of sands, gravels, and smaller boulders. The river flow in the Rio Canete here is high year-round with discharge at this time perhaps approaching base flow. Fluctuations in river flow throughout the catchment may well be dampened by the presence of so many lakes along the valley bottom.

There is no agricultural activity in the valley or valley sides. Otherwise, extensive pastoralism dominates rural land use throughout the headwater areas.

At these elevations the fauna and flora are now more typical of the high Andes. Andean goose, Yellow-billed Teal, Yellow-billed Pintail, Puna teal, Andean Coot, Spot-winged Pigeon, Black-winged Ground Dove and Mountain Caracara are now commonly observed.

RC15 View upstream Site RC15 - Study site location: lake outflow. (John Forrest)

Site RC15 - the study site & view upstream. (John Forrest) Site RC15 - the study site & view upstream. (John Forrest)

RC15 View upstream Site RC15 - View upstream. (John Forrest)

image Site RC15 - View downstream. (John Forrest)