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|
|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|
|Total Dissolved Solids (ppm)||90||91|
|Alkalinity (mg/l CaCO₃)||74 (1.6N)||-|
|Alkalinity Field Tester (ppm/ CaCO₃)||-||-|
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.
pH readings of 9.43 in November 2019, are more alkaline than in the main channel. This does require further investigation to identify the causes of this. However, 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 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 03 - the Tupe subcatchment. (Eustace Barnes)
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 - View upstream from the study site. (John Forrest)