RT09A - Lower Alis

Site Code: RT09A. GPS: S12°28671, W75°787584. Elevation: 3254m asl.

Water Quality Data

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

T9a July 2019 November 2019 November 2021
Season: Austral Winter Austral Summer Austral Summer
Date: 11.07.2019 21.11.2019 15.11.21
Time: 16.25pm 15.45pm 12.30pm
Width (m) 8.0 6.0 7.5
Depth (Av.) (m) 0.64 0.90 0.63
CSA (Av.) (m²) 5.09 5.40 4.725
Velocity (Av.) (m/s) 1.17 0.68 0.73
Discharge (Av.) (m³/s) 5.958 3.661 3.449
Riverbed sediment Cobbles & Boulders Cobbles & Boulders Boulders
Temp. (Atmospheric) (°C) 16 24 19
Temp. (Water) (°C) 11.24 12.69 12.22
Atmospheric pressure (mbar) 599 680  
Dissolved oxygen (mg/l) 5.04 3.63 6.06
Dissolved oxygen (%) 67.6 59.6 82.1
pH - 8.35 8.05
Conductivity (µS/cm) 602 625 803
Total Dissolved Solids (ppm) 301 312 402
ORP (mV) 349.3 154.5 143.3
Turbidity Clear: Clear: Clear:
Alkalinity (mg/l CaCO₃) 193 (1.6N) - 206 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) - - -

Data Analysis

Discharge fluctuations at this point along the Rio Alis reflect the timing, with discharge slowing and reducing as the dry season progresses.

At well over 3200m asl the DO readings at T9a fall within the range to be expected. It again shows the fall in DO readings from July to November for this tributary. Data from this site may reflect the significantly higher temperatures in November, although water temperatures were similar.

The measurements for conductivity and total solids are slightly on the high side and may reflect the fact that this site lies below a more significant settlement. Sewage outfall and other pollutants from domestic waste may enter the channel here. However, despite this the readings for water quality are still good.

Average pH readings of above 8.0 in November are as expected. At these levels the alkalinity of the river is suitable for aquatic life.

Site Description

Sites T9a lies in the arid temperate zone just below the small town of Alis at 3231m asl. It is located in the temperate zone in a narrow canyon. This being produced by rapid downcutting through a highly fractured upfold. The valley at this point is v-shaped with high sections of cliffs lining the valley. Above this point the valley widens out at the site of the settlement of Alis. The bed load in the river channel is comprised of fluvio-glacial boulders, gravels, and sands. The river flow in the Rio Alis is year-round, despite having been reduced by significant abstraction to supply the village of Alis.

There is limited agricultural cultivation. Historically, the terraced valleys would have been cultivated more intensively. Changes in agricultural production reflecting population decline in both the early period of Hispanic colonisation and, more recently, rural out-migration. 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 with stands of Eucalypts. Above the uneven flood-plain valley sides are dominated by arid scrub and relictual pacific woodlands in sheltered ravines. 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, and Black-throated Flowerpiercer are common here.

Tributary T09 - the Alis subcatchment. (Eustace Barnes) Tributary 09 - the Alis subcatchment. (Eustace Barnes)

Site T09A - the study site location. (John Forrest) Site T09A - the study site location just below the town of Alis. (John Forrest)

Site T09A - the study site. (John Forrest) Site T09A - the study site. (John Forrest)

Site T09A - View downstream from the study site. (John Forrest) Site T09A - View downstream from the study site. (John Forrest)

Site T09A - View upstream from the study site. (John Forrest) Site T09A - View upstream from the study site. (John Forrest)