RC05 - Tambo

Site Code: RC05. GPS: S12°80400, W75°896007. Elevation: 1135m asl.

Water Quality Data

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

RC05 July 2019 November 2019
Season: Austral Winter Austral Summer
Date: 10.07.2019 18.11.2019
Time: 13.20pm 16.00pm
Width (m) 38 18
Depth (Av.) (m)   0.234
CSA (Av.) (m²)   4.212
Velocity (Av.) (m/s)   0.679
Discharge (Av.) (m³/s) 7.5 2.867
Riverbed sediment Cobbles & boulders Cobbles & boulders
Temp. (Atmospheric) (°C) 28 29
Temp. (Water) (°C) 20.58 23.39
Atmospheric pressure (mbar) 885 852
Dissolved oxygen (mg/l) 6.42 5.47
Dissolved oxygen (%) 81.6 76.7
pH 6.12 8.75
Conductivity (µS/cm) 352 418
Total Dissolved Solids (ppm) 176 209
ORP (mV) 356.7 137.7
Turbidity Clear Clear
Alkalinity (mg/l CaCO3) Pink to colourless 135 (1.6N) -

Data Analysis

Discharge at this site is significantly impacted by the El Platanal HEP water abstraction and seasonal abstraction for agricultural irrigation in the valley above Catahuasi. Input from the Rio Tupe is low and water taken out is high, as the Catahuasi district is an agricultural district producing fruit and vegetables more widely across the valley.

At just over 1100m asl the DO readings at RC05 are as expected for both July and November data sets. The raised elevation and great fluctuations in daily temperature in such narrow and sheltered valleys will produce fluctuations in maximum absolute oxygen capacity and, in consequence, percentage saturation that therefore fluctuates with that rhythm. At DO levels from 5.45-6.6 mg/l and 75-83\% oxygen saturation aquatic vertebrates survive and invertebrates thrive.

The conductivity reading at this site 414-419 µS/cm is as expected at this altitude.

pH readings of 8.76 November are as expected. At these levels the alkalinity of the river is suitable for aquatic life and not approaching the tolerances of most aquatic vertebrates and invertebrates. The July data requires confirmation.

Site Description

Site RC05 is located just below the town of Catahuasi in the arid upper tropics. The Rio Canete, at this point is downriver of limited intensively farmed lands. The valley flood plain above Catahuasi is wider and more intensively farmed. The use of pesticides and fertilizers is probably only higher in the various sub-catchments in the temperate zone, including Yauyos, Huantan, Laraos, Alis etc. The valley still has a narrow steeply v-shaped profile with a high river cliff on the south bank, indicating previous periods of flooding. As elsewhere in the drainage basin discharge is highly seasonal. Discharge measurements in February-March are considerably greater. The channel itself is choked with large boulders and rocks from landslides and previous flooding events.

The banks are lined with scattered willow and some acacia scrub. The cultivation of crops is exclusively for subsistence farming in the marginal small groups forced onto the poorer soils. The production of maize, bananas dominate with smaller areas of avocado production. As with elsewhere in the catchment, there is little or no natural vegetation remaining. The fauna and flora in the valley are depauperate with relictual west flanks endemics. The impact of water quality on the health of the environment and populations of wildlife occupying these lands is the subject of some aspects of our study here.

RC05 View upstream Site RC05 - Study site location: due west of the small settlement of Tambo. (John Forrest)

Site RC05 - the study site. (John Forrest) Site RC05 - the study site. (John Forrest)

RC05 View upstream Site RC05 - View upstream. (John Forrest)

RC05 View downstream Site RC05 - View downstream. (John Forrest)