RC12 - Villa da Arma

Site Code: RC12. GPS: S12°29821, W75°814258. Elevation: 3053m asl.

Water Quality Data

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

RC12 July 2019 November 2019 November 2021
Season: Austral Winter Austral Summer Austral Summer
Date: 11.07.2019 20.11.2019 15.11.21
Time: 15.30pm 12.15pm 11.00am
Width (m) 14 18 12
Depth (Av.) (m) 0.97 0.80 0.91
CSA (Av.) (m²) 13.56 14.35 10.87
Velocity (Av.) (m/s) 1.10 1.06 0.90
Discharge (Av.) (m³/s) 14.96 15.235 9.836
Riverbed sediment Cobbles & Boulders Cobbles & Boulders Mainly boulders
Temp. (Atmospheric) (°C) 18 24.5 18
Temp. (Water) (°C) 11.48 13.13 12.95
Atmospheric pressure (mbar) 605 708  
Dissolved oxygen (mg/l) 5.07 3.99 6.67
Dissolved oxygen (%) 66.0 64.1 88.6
pH 6.13 8.67 8.27
Conductivity (µS/cm) 525 457 602
Total Dissolved Solids (ppm) 263 229 301
ORP (mV) 347.13 154.57 166.7
Turbidity Clear: Clear: Clear:
Alkalinity (mg/l CaCO₃) 167 (1.6N) - 143 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) - - -

Data Analysis

Discharge at this point along the Rio Canete did not increase July to November 2019, indicating rains had not started in the Rio Canete headwaters, in contrast to conditions in the lower tributary headwaters. The flow recorded may therefore represent base flow. The rains from the end of November to the end of March then recharge the catchment, and raise discharge to a peak in April. The sample point lies just below the confluence with the Rio Alis.

At over 3000m asl the DO readings at RC12 are low but fall within the range to be expected for both July and November 2019 data sets. The DO levels are very similar for both sample times. Conductivity readings at this site range from 457-527 µS/cm. This is high, but RC12 is in the upper mid-catchment.

Mildly alkaline pH readings are to be expected for rivers generally. The July data requires confirmation.

Site Description

Site RC12 lies in the Rio Canete valley at 3032m asl in the arid temperate zone. It is just below the confluence with the Rio Alis at Tinco Alis. The valley at this point is narrow with a pronounced v-shaped profile and steep valley sides. River flow is year-round and fast at this point, although January to March flows are much greater.

The level flood-plain lands are only cultivated to a limited extent. There is some limited pastoralism and subsistence production of maize and quinua but little else. The riverbanks and nearby fields are lined with Alders, tall thorn scrub and scattered Eucalyptus sp.

Above the narrow flood-plain valley sides are arid, supporting a xeric vegetation with increased woody shrubs and trees lining some of the more sheltered ravines. The north facing slope is rather more densely covered with shrubs and trees associated with the relictual pacific woodlands found a little higher up the valley. This site retains the typical avifauna of these elevations as outlined for sites RC10 and RC11.

RC12 View upstream Site RC12 - Study site location: in front of the Villa de Arma lodge, below the bridge. (John Forrest)

Site RC12 - the study site. (John Forrest) Site RC12 - the study site. (John Forrest)

RC12 View upstream Site RC12 - View upstream. (John Forrest)

image Site RC12 - View downstream. (John Forrest)