RT08B - Middle Laraos (Below Puente Union)

Site Code: RT08B. GPS: S12°36259, W75°763129. Elevation: 3730m asl.

Water Quality Data

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

T8b November 2019 November 2021
Season: Austral Summer Austral Summer
Date: 21.11.2019 16.11.21
Time: 9.00am 13.30pm
Width (m) 7.0 8.0
Depth (Av.) (m) 0.12 0.19
CSA (Av.) (m²) 0.81 1.52
Velocity (Av.) (m/s) 0.17 0.44
Discharge (Av.) (m³/s) 0.138 0.669
Riverbed sediment Cobbles & Boulders Cobbles & Boulders
Temp. (Atmospheric) (°C) 22 21
Temp. (Water) (°C) 10.61 11.05
Atmospheric pressure (mbar) 700  
Dissolved oxygen (mg/l) 3.45 5.80
Dissolved oxygen (%) 52.8 80.7
pH 8.33 8.06
Conductivity (µS/cm) 287 379
Total Dissolved Solids (ppm) 143 188
ORP (mV) 136.6 156.4
Turbidity Clear: Clear:
Alkalinity (mg/l CaCO₃) - 118 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) - -

Data Analysis

Discharge at this point along the Rio Laraos combines the two measurements from the stream just above Puente Union and the spring (mantanial).

At well over 3500m asl the DO readings at T8b fall within the range to be expected. The measurements for DO, conductivity and total solids are also as expected.

Our next samples from this sub-catchment may be from the higher headwaters.

Site Description

Sites T8b and T8c lie within a few metres of each other in the upper Rio Laraos at 3733m asl, above the settlement of Laraos. They are located in the temperate zone just beneath extensive polylepis groves, puna grasslands and bofedales. Above this point the valley has the features and u-shaped profile typical of once glaciated valleys. The bed load in the river channel is comprised of fluvio-glacial boulders, gravels, and sands. At this site, the water flow in the Rio Laraos is year-round and delivers all the water needs for the village of Laraos below. The spring is a sacred site and likewise used by local people.

There is little or no agricultural cultivation along this section of the valley. There is limited pastoralism and field rotation employed for the production of potatoes and quinua. The riverbanks are dominated by riparian scrub and small alders. Above the uneven flood plain valley sides are arid temperate, supporting a scrub and extensive polylepis groves on the higher slopes. The low levels of agricultural activity here results from rural out-migration and depopulation.

The hillsides are terraced and, in the past have supported intensive irrigated agriculture. This site displays a fauna and flora typical of temperate elevations. Chiguanco Thrush, House Wren and Hooded Siskin remain. Cream-winged and White-winged Cinclodes, Striated Earthcreeper, Peruvian Sierra Finch, Plumbeous Sierra Finch, Band-tailed and Plain-coloured Seedeaters, Black-throated Flowerpiercer are now common here. In the polylepis groves White-cheeked Cotinga and Giant Conebill are easily found and with further fieldwork other polylepis obligates may be found. Andean Parakeet, Black-winged Ground Dove, White-browed Chat Tyrant, Tufted Tit Tyrant, and Rusty-crowned Tit Spinetail are commonly observed. A more detailed inventory of avifauna will be produced for each site in subsequent reports.

In the upper parts of this sub-catchment agriculture is pastoral. The road is used to access two areas of mining, the Mina Yauricocha and Mina Huancapallca, although only the latter may impact on this sub-catchment.

Site T08B - the study site location. (John Forrest) Site T08B & T08C - the study site locations: T08B just below Puente Union & T08C just above Puente Union - in the mantanial (Nov.2019) & just above the mantanial (Nov.2021). (John Forrest)

Site T08B - the study site. (John Forrest) Site T08B - the study site. (John Forrest)

Site T08B - View downstream from the study site. (John Forrest) Site T08B - View downstream from the study site. (John Forrest)

Site T08B - View upstream from the study site. (John Forrest) Site T08B - View upstream from the study site. (John Forrest)