RC09 - Below Tinco

Site Code: RC09. GPS: S12°42661, W75°853404. Elevation: 2624m asl.

Water Quality Data

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

RC09 July 2019 November 2019 November 2021
Season: Austral Winter Austral Summer Austral Summer
Date: 11.07.2019 20.11.2019 14.11.21
Time: 10.00am 15.35pm 9.30am
Width (m)   24.0 29.0
Depth (Av.) (m)   0.27 0.65
CSA (Av.) (m²)   6.58 18.85
Velocity (Av.) (m/s)   0.87 1.11
Discharge (Av.) (m³/s)   5.747 20.924
Riverbed sediment   Cobbles, boulders & gravel Mainly cobbles
Temp. (Atmospheric) (°C) 24 19 19
Temp. (Water) (°C) 10.78 14.04 13.10
Atmospheric pressure (mbar) 740 750  
Dissolved oxygen (mg/l) 6.43 4.73 7.09
Dissolved oxygen (%) 76.6 73.7 91.0
pH 5.91 8.70 8.34
Conductivity (µS/cm) 479 423 583
Total Dissolved Solids (ppm) 239 211 292
ORP (mV) 353.2 152.9 63.1
Turbidity Clear: Clear: slightly milky Clear:
Alkalinity (mg/l CaCO₃) 206 (1.6N) - 122 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) - - 135

Data Analysis

Discharge at this point along the rio Canete is as expected for these times of year with discharge gradually reducing to baseflow by November just before the rains start in the headwater areas. The periods we have sampled as such fall within the dry season.

At just over 2400m asl the DO readings at RC09 fall within the range to be expected for both July and November data sets. Again, the increased elevation and diurnal fluctuations in temperature in narrow, sheltered sections of the valley will produce fluctuations in maximum absolute oxygen capacity and, in consequence, percentage saturation. This then fluctuates with that rhythm accordingly. The DO levels appear to be rather variable at this site, perhaps indicating that the conditions for life are likewise rather variable.

The conductivity readings at this site (400-479 µS/cm) is high for this elevation.

pH readings of 9.25 in November 2019 are high. At these levels the alkalinity of the river remains suitable for aquatic life and not approaching the tolerances of most aquatic vertebrates and invertebrates. The July data requires confirmation.

Site Description

Site RC09 is located in the upper sub-tropics, below the settlement of Tinco and the bridge of the same name. It lies in the Rio Canete valley at 2430m asl and just below the confluence with the Rio Huantan. The valley at this point has a pronounced v-shaped profile and is opening out after flowing through a canyon above Tinco. River flow is high and fast at this point with a variable extent of shingle banks, depending on the time of year.

There are insignificant areas of cultivation lining the river which is dominated by riparian woodlands and scrub. 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 areas. Along the valley bottom, the vegetation is dominated by Salix and endemic species typical of this elevation. A few Eucalyptus have been planted but otherwise this remains largely natural. Of the natural vegetation there are clumps of river cane and willows along the river edge along with increasing numbers of species typical of the relictual pacific woodlands found in the temperate zone. The lack of degradation and agricultural activity at this point may reflect seasonal unpredictability of river levels and discharge here. This being made all the more marked because it lies close to the confluence of the Rio Canete and Rio Huantan.

RC09 View upstream Site RC09 - Study site location: just below Puente Aquicha (Tingo). (John Forrest)

Site RC09 - the study site. (John Forrest) Site RC09 - the study site. (John Forrest)

RC09 View upstream Site RC09 - View upstream. (John Forrest)

RC09 View downstream Site RC09 - View downstream. (John Forrest)