RT03A - Lower Tupe (Catahuasi)

RT03A - Lower Tupe (Catahuasi)

Site Code: RT03A. GPS: S12°80101, W75°891699. Elevation: 1184m asl.

Water Quality Data

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

T3a July 2019 November 2019 November 2021
Season: Austral Winter Austral Summer Austral Summer
Date: 10.07.2019 18.11.2019 10.11.21
Time: 14.00pm 16.30pm 14.00pm
Width (m) 8.0 6.0 RIVER DRY
Depth (Av.) (m) 0.10 0.06  
CSA (Av.) (m²) 0.78 0.38  
Velocity (Av.) (m/s) 0.06 0.04  
Discharge (Av.) (m³/s) 0.046 0.014  
Riverbed sediment Cobbles & boulders Cobbles & boulders  
Temp. (Atmospheric) (°C) 24 30  
Temp. (Water) (°C) 19.9 22.0  
Atmospheric pressure (mbar) 879 845  
Dissolved oxygen (mg/l) 6.59 4.80  
Dissolved oxygen (%) 81.6 64.9  
pH - 9.41  
Conductivity (µS/cm) 181 182  
Total Dissolved Solids (ppm) 90 91  
ORP (mV) 341.0 159.8  
Turbidity Clear: Clear:  
Alkalinity (mg/l CaCO₃) 74 (1.6N) -  
Alkalinity Field Tester (ppm/ CaCO₃) - -  

Data Analysis

Discharge at this site is unaffected by water abstraction for the El Platanal HEP plant but is impacted by water abstraction in the upper Tupe above Catahuasi. There are two small isolated communities at Tupe and Aiza with a mainly subsistence production economy. Discharge in the Rio Tupe is highly variable - in July to November levels are very low, in January the river becomes more of a torrent.

At just over 1200m asl the DO readings at T3a are as expected for both July and November data sets. Low water levels in the river at this time (November 2019) contributed to a degree of stagnation and eutrophication in some sections of the channel. The raised elevation and great fluctuations in daily temperature in such narrow and sheltered valleys does 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 readings at this site (180-183 µS/cm) are low, as would be expected for a relatively small sub-catchment.

An average pH reading of 9.41 in November 2021 was the highest recorded in the Canete valley indicating that it is more alkaline than the main channel. This requires further investigation to identify the causes. However, at these levels the alkalinity of the river is still suitable for aquatic life and not approaching the tolerances of most aquatic vertebrates and invertebrates.

Site Description

Site T3a is located adjacent to the town of Catahuasi at 1220m asl in the arid upper tropics. This sub-catchment is one of the smallest being sampled. It is only occupied by the small communities of Tupe and Aiza. These are isolated communities that have only recently been fully connected to the local economy with the construction of a road. The valley has a deeply incised v-shaped profile and valley sides are steep and rocky.

At this point in the sub-catchment farming is not practised to any great extent. There are smaller orchards producing avocados and fruit with some plantains being grown. As elsewhere in the drainage basin, discharge is highly variable with a marked seasonality. Discharge measurement from January to March are considerably greater. The channel itself is choked with large boulders and rocks from landslides and earlier flooding events.

Tributary T03 - the Tupe subcatchment. (Eustace Barnes) Tributary 03 - the Tupe subcatchment. (Eustace Barnes)

Site T03A - the study site location. (John Forrest) Site T03A - the study site location: just beside the settlement of Catahuasi and below the main highway bridge. (John Forrest)

Site T03A - the study site. (John Forrest) Site T03A - the study site. (July 2019) (John Forrest)

Site T03A - View upstream from the study site. (John Forrest) Site T03A - View upstream from the study site. (July 2019) (John Forrest)