RT07A - Lower Huantan

Site Code: RT07A. GPS: S12°42603, W75°848726. Elevation: 2679m asl.

Water Quality Data

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

T7a July 2019 November 2019 November 2021
Season: Austral Winter Austral Summer Austral Summer
Date: 11.07.2019 20.11.2019 14.11.21
Time: 11.00am 15.35pm 15.00pm
Width (m) 2.0 4.0 12.00
Depth (Av.) (m) 0.26 0.19 0.27
CSA (Av.) (m²) 0.51 0.75 3.23
Velocity (Av.) (m/s) 0.60 0.56 0.32
Discharge (Av.) (m³/s) 0.308 0.424 1.023
Riverbed sediment Mainly Boulders Mainly Boulders Mainly Boulders
Temp. (Atmospheric) (°C) 17 18 22
Temp. (Water) (°C) 8.30 12.97 16.32
Atmospheric pressure (mbar) 725 745  
Dissolved oxygen (mg/l) 6.04 4.69 6.21
Dissolved oxygen (%) 69.3 73.7 85.7
pH - 8.56 8.33
Conductivity (µS/cm) 180 173 289
Total Dissolved Solids (ppm) 90 86 145
ORP (mV) 354.1 145.5 91.6
Turbidity Clear: Clear: Clear:
Alkalinity (mg/l CaCO₃) - - 102 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) - - -

Data Analysis

Discharge at this point along the Rio Huantan increased from July to November, suggesting that the rains had already started in the headwaters of this sub-catchment. The periods we have sampled as such fall principally within the dry season. However, rains in the high sierra do begin from mid-October.

At just over 2400m asl the DO readings at T7a 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, consequently, the 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 (180-185 µS/cm) are as expected for a sub-catchment.

Average pH readings of approximately 8.5 in November are as expected. At these levels the alkalinity of the river is highly suitable for aquatic life and indicative of clean water.

Site Description

Site T7a lies in the Rio Huantan valley at 2572m asl and just above the confluence with the Rio Canete. It is located in the upper sub-tropics, above the settlement of Tinco in a picturesque valley. The valley at this point is very narrow with a pronounced v-shaped profile and steep river cliffs cut down through highly fractured strata. Bed load in the river channel is comprised of rocks predominantly with huge boulders. River flow in the Rio Huantan is year-round and delivers a significant proportion of river discharge at this point in the catchment.

There is little or no agricultural cultivation along this section of the Rio Huantan. The study site which is dominated by riparian Alders, Agaves, and tall thorn 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 ravines. The lack of agricultural activity results from the lack of level ground and dominance of rocks and boulders lying across the steep slopes. This site retains the typical avifauna of the lower elevations with Scrub Blackbird, Black-necked Woodpecker, Golden Grosbeak, Chiguanco Thrush, House Wren, and Hooded Siskin being species that reflect a transitional community between the sub-tropics and temperature zone.

In the upper parts of this sub-catchment agriculture is low intensity and traditional and rural population low, having been subject to rural drift. In the headwaters there is a mining camp at Anexo Atcas. This mine may well impact water quality in the Rio Huantan as might the Mina Corihuami located on the Rio Huantan watershed. Samples from our sample site just above Anexo Atcas are yet to be collected.

Tributary T07 - the Huantan subcatchment. (Eustace Barnes) Tributary 07 - the Huantan subcatchment. (Eustace Barnes)

Site T07A - the study site location. (John Forrest) Site T07A - the study site location just above the Huantan turn off at Tingo. (John Forrest)

Site T07A - the study site. (John Forrest) Site T07A - the study site. (July 2019) (John Forrest)

Site T07A - View downstream from the study site. (John Forrest) Site T07A - View downstream from the study site. (July 2019) (John Forrest)

Site T07A - View upstream from the study site. (John Forrest) Site T07A - View upstream from the study site. (July 2019) (John Forrest)