RT09A.M - Lower Alis (Manantial)

Site Code: RT09A.M. GPS: S12°266150, W75°768910. Elevation: 3415m asl.

Water Quality Data

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

T9aM November 2021
Season: Austral Summer
Date: 16.11.21
Time: 9.00am
Width (m) 18.0
Depth (Av.) (m) 0.16
CSA (Av.) (m²) 2.88
Velocity (Av.) (m/s) 0.62
Discharge (Av.) (m³/s) 1.786
Riverbed sediment -
Temp. (Atmospheric) (°C) 17
Temp. (Water) (°C) 12.45
Atmospheric pressure (mbar)  
Dissolved oxygen (mg/l) 3.22
Dissolved oxygen (%) 45.33
pH 7.16
Conductivity (µS/cm) 920
Total Dissolved Solids (ppm) 460
ORP (mV) 150.7
Turbidity Clear:
Alkalinity (mg/l CaCO₃) 210 (1.6N)
Alkalinity Field Tester (ppm/ CaCO₃) -

Data Analysis

Discharge at this point on the Rio Alis was significant suggesting that the rains may have started higher up this sub-catchment. The low DO readings at T09aM are as expected for a river that has just emerged from underground but are too low for many aquatic species. The conductivity readings at this site (920 µS/cm) is high for a spring at this altitude within the sub-catchment. It suggests a degree of dissolved salts and other compounds resulting from subterranean weathering and erosion. It is above the ideal level for aquatic life and direct human consumption. The pH reading of 7.16, is lower than expected. At this level the water is tending towards acidic and away from alkaline conditions which are less suited to aquatic life and human consumption.

Site description

Site T09aM is a manantial which flows for approximately 50 metres from where it emanates in to the Rio Alis. It lies in the Rio Alis valley at 3415m asl, a short distance above the small settlement of Alis. The valley at this point is very narrow with a v-shaped profile, very steep sides and a very narrow flood-plain. The manantial is located on the south side of the valley and fans out as it flows from the spring in to the river. The manantial appears to drain a significant area to the south of the Alis valley and flows year-round, delivering a constant input to the Rio Cañete. The study site is dominated by eucalyptus and tall natural scrub. Water is drawn immediately from the manantial to supply the nearby settlement of Alis thereby reducing the discharge that it is possible to measure.

Site T9A.M - the study site. (John Forrest) Site T09A.M - the study site (Nov.2021). (John Forrest)