RC00 - Rio Cañete Estuary

This site has been sampled at two points. RC-00a and RC-00b. These sites are very different in character. RC-00b. Sample point RC-00a, indicated by a blue point on the above image principally flows from the village of Herbay Bajo and associated lands. The sample point RC-00b, indicated by a red point on the above image better represents the cumulative character of the water geochemistry for the catchment as a whole. We will continue to sample both of these points.

It should be noted that the geochemical character of channel water is increasingly determined by local natural and anthropogenic factors as one descends to the estuary, notwithstanding the constant input of ground waters. That is, since a high proportion of water is abstracted in the upper and mid-catchment for irrigation thereby reducing the impact of those sections of the drainage basin. Thus, it is conditions within each discreet area that are more important for the analysis of water geo-chemistry. As such, even in the lower catchment from RCOO to RC03 it seems to be the case that local geological character and local anthropic activities obtain a greater significance that they might were conditions in the mid and upper catchment less disturbed.

Site RC00a. Rio Canete estuary – Herbay Bajo (South side)

Site Code: RC00a.
GPS: S13 07.707 W76 23 922.
Elevation 5masl.

Fig 1a. RC – 00a  Herbay Bajo on the south side of the river (Eustace Barnes).
Fig 1a. RC – 00a Herbay Bajo on the south side of the river (Eustace Barnes).

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

Austral Winter – July 2019. RC-00a
This is a minor side channel that drains from the village of Herbay Bajo.
Water/river data summary. Data/time collected: 09/07/2019 at 9.00am
River discharge. Southern Channel (Width – 6m. Average depth 0.095. Average velocity 0.159 (metres per second). Cross sectional area of 0.568m2. Gives a discharge of 0.09 cubic meters per second). The discharge of the main channel is roughly 4.0 cubic metres per second. River discharge, as with most rivers on the west flank of the Andes, is significantly affected by abstraction for agricultural irrigation.

River bed type. Stones and Boulders across a broad braided channel.
Temperature; Atmospheric – 20 C, River water 19.16 C.
Atmospheric pressure – 1015mbar
Dissolved Oxygen. 4.71, 4.42, 4.79Mg/l, 50.7, 47.7, 51.7%
pH – 5.5, 5.5, 5.54
Conductivity (micro siemens) 689, 700, 698
Total solids (ppm) 344, 350, 349
ORP (millivolts) 354.6, 354.4, 353.6
Turbidity FNU – Not taken. PSU – Not taken.
Test strips - Fe mg/l 0.0, Cu mg/l – 0.0, NH4 mg/l – 0.0.
Alkalinity (mg/l CaCO3) Pink to colourless 262 (Cartridge used – 1.6N).
Nitrate cell tests
Nitrates. Mg/l NO3 – 2.2, mg/l, N03-N 7.6 (quality check – 6.79mg/l NO3, 7.9 NO3-N)
Ammonia. Mg/l NH4 – under range, mg/l NH4-N – under range. (Quality check – over range for both).

Data Analysis

It is the case that the amount of dissolved oxygen at 100% saturation at sea level and at 20° C would be 9.03 mg/L. However, at 4.42-4.79mg/l the DO reading are on the low side. As both water and atmospheric temperature was 19.16-20,0 C significant factors are reducing DO levels at this site. At 4.5mg/l dissolved oxygen and 50% oxygen saturation aquatic vertebrates survive and invertebrates thrive. High concentrations of nutrients (particularly phosphorus and nitrogen) fuel algae blooms, which initially boosts dissolved oxygen levels but then rapidly reduce DO. When the algae die, bacterial decomposition spikes, using up most or all of the dissolved oxygen available. This creates an anoxic, or oxygen-depleted, environment where few organisms survive. Such nutrient levels can occur naturally but are more often caused by pollution from fertilizer runoff or poorly treated wastewaters which could apply to this site below Herbay Bajo. At these recorded levels, denitrification takes place as bacteria use nitrates to decompose organic matter. These conditions are referred to as ‘dead zones’ and are often found near larger human populations in estuaries and coastal zones. The Conductivity reading at this site is 689-700 Ms. The level of conductivity in the Rio Canete at RC-00 is an indicator of significant contamination from waste waters and agricultural runoff. Generally, agricultural runoff and sewage will increase conductivity due to the additional chloride, phosphate and nitrate ions. The Nitrate levels recorded at RC-00 were 2.2mg/l. NO3. Throughout the catchment nitrate levels ranged from ‘under range’ to 6.79mg/l NO3 emphasizing the significance of both irrigated agriculture and sewage outfall from the city of Canete.
At pH 5.4-5.5 the acidity of river waters is well withing the tolerance limit for life and not approaching the tolerances of most aquatic vertebrates and invertebrates.

Site description

Site RC00a is located on the south side of the Rio Canete below the new Pan American highway bridge. It is at sea level in the arid tropical zone. The Rio Canete at this point is lined with scrub and less intensively farmed areas as a consequence of the impact of both catastrophic flooding and marine ingression. Within a few hundred meters land is irrigated and agriculture of an intensive industrial nature. The valley at this point is a broad flat flood plain to the north bounded to the south by a steep river cliff. The channel flow is highly variable from the dry season to the wet season, depending on water abstraction for agriculture and urban demand. The channel itself is highly braided at this time and made up largely of gravel and smaller boulders. The river does hold water year-round. Discharge at the end of September is low at the sample point at about 4.5 cubic meters per second but would be 12 cubic meters per second were no water taken out. During the wet season discharge is considerably higher. The banks are lined with river cane and scattered areas of stunted willow. Cultivation a short distance up river is intense and fully irrigated. The production of potatoes, maize, ajo (garlic), aji (peppers), avocado dominates land use. There are smaller areas of sugar cane, a crop which dominates land use in the lower Fortaleza valley. There is little or no natural vegetation remaining in the lower valley and much of what was open desert has been irrigated and no highly productive agricultural lands. The water quality in the river at lower elevations is severely impacted by agricultural run-off and sewage disposal. The wider environment and fauna in the valley are largely determined by agriculture with many species expanding their range and abundance to occupy newly created agricultural lands. Desert fauna and flora has decreased accordingly. 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.

Site photos.

Fig 1b. Site RC00a – looking across the Rio Canete estuary – showing barrier beach and lagoons behind. (Eustace Barnes).
Fig 1b. Site RC00a – looking across the Rio Canete estuary – showing barrier beach and lagoons behind. (Eustace Barnes).

The Rio Canete estuary, shown here, is very important for the reproduction of Cryphiops caementarius, the Northern River shrimp. It is also an important site for breeding and migratory species of birds. As such the quality of water at this site requires careful monitoring. Many factors are instrumental in determining water quality in the estuary.

As part of our field work we have collected specimens of Northern River Shrimp, Cryphiops caementarius to assess the trophic transfer of trace metals. We aimed to collect 350gm of muscle flesh and a similar weight of carapace from however many individuals we needed to catch. Employing local fisherman we arranged for him to catch the necessary number of River Shrimps at RC00b and two other sites in the lower catchment; Puente Socsi (RC-02b) and Puente Catapalla (RC-02c) (confirm coding for these sites).

Fig 1c.  Site RC00a – looking towards the sea –  lagoons in the far distance and the secondary channel in the foreground (Eustace Barnes).
Fig 1c. Site RC00a – looking towards the sea – lagoons in the far distance and the secondary channel in the foreground (Eustace Barnes).
Fig 1d. Site RC00a  – Camarones catchers catching camarones in the estuary lagoons. In the estuary lagoons it is primarily females that are being caught. See photos below of specimens caught the same day  (Eustace Barnes).
Fig 1d. Site RC00a – Camarones catchers catching camarones in the estuary lagoons. In the estuary lagoons it is primarily females that are being caught. See photos below of specimens caught the same day (Eustace Barnes).
Fig 1e. Site RC00a – Part of the fieldwork team at the sample collection point (Eustace Barnes).
Fig 1e. Site RC00a – Part of the fieldwork team at the sample collection point (Eustace Barnes).
Fig 1f. Site RC00a – female Cryphiops caementarius caught at the estuary lagoons. (Eustace Barnes).
Fig 1f. Site RC00a – female Cryphiops caementarius caught at the estuary lagoons. (Eustace Barnes).
Fig 1g RC00a – the estuarine lagoons are important for a wide variety of waterbirds:  Little Blue Heron, Snowy Egret and Puna Ibis shown above. (Eustace Barnes).
Fig 1g RC00a – the estuarine lagoons are important for a wide variety of waterbirds: Little Blue Heron, Snowy Egret and Puna Ibis shown above. (Eustace Barnes).
Fig h. Site RC00a. Other wetland species found in the estuary include Yellow-crowned Night Heron, Black-crowned night Heron and Common Gallinule (Eustace Barnes).
Fig h. Site RC00a. Other wetland species found in the estuary include Yellow-crowned Night Heron, Black-crowned night Heron and Common Gallinule (Eustace Barnes).

Site RC00b. Rio Canete estuary – Boca cdel Rio (North side)

Site Code: RC00b.
GPS: S13 07.589 W76 24 026.
Elevation 5masl.

Fig 1i.RC-00b. Boca del Rio on the north side of the river looking southwards(Eustace Barnes).
Fig 1i.RC-00b. Boca del Rio on the north side of the river looking southwards(Eustace Barnes).

Austral Summer - November 2019. RC-00b
This is the principal channel. Water quality seems to be quite different from the minor channel samples earlier in the year in July.
Water/river data summary. Data/time collected: 17/11/2019 at 11.00am
River discharge. Southern Channel (Width – 22m. Average depth 0.123. Average velocity 0.435 (metres per second). Cross sectional area of 2.706m2. Discharge of 1.123 cubic meters per second). This measurement would seem to be on the low side. A rough estimate would place discharge at about 3.0 cubic metres per second.

River bed type. Stones and Boulders across a broad braided channel.
Temperature. Atmospheric – 24.5 C, River water 22.3, 22.2, 22.2 C.
Atmospheric pressure – 1009mbar
Dissolved Oxygen. 4.71, 4.42, 4.79Mg/l, 50.7, 47.7, 51.7%
pH – 8.55, 8.68, 8.79
Conductivity (micro siemens) 489, 490, 510
Total solids (ppm) 245, 245, 255
ORP (millivolts) 184.9, 185.8, 186.6
Turbidity FNU – Not taken. PSU – Not taken.
Alkalinity (mg/l CaCO3) Pink to colourless 170 (Cartridge used – 1.6N).

Data Analysis. It is the case that the amount of dissolved oxygen at 100% saturation at sea level and at 20° C would be 9.03 mg/L. However, at 4.42-4.79mg/l the DO reading are on the low side. As both water and atmospheric temperature was 22.2 – 24.5 C there are some factors reducing DO levels at this site. At 4.42 – 4.79mg/l dissolved oxygen and 50% oxygen saturation aquatic vertebrates survive and invertebrates thrive. High concentrations of nutrients (particularly phosphorus and nitrogen) fuel algae blooms, which initially boosts dissolved oxygen levels but then rapidly reduce DO. When the algae die, bacterial decomposition spikes, using up most or all of the dissolved oxygen available. This creates an anoxic, or oxygen-depleted, environment where few organisms survive. Such nutrient levels can occur naturally but are more often caused by pollution from fertilizer runoff or poorly treated wastewaters which could apply to this site below Herbay Bajo. At these recorded levels, denitrification takes place as bacteria use nitrates to decompose organic matter. These conditions are referred to as ‘dead zones’ and are often found near larger human populations in estuaries and coastal zones. The Conductivity reading at this site is 489-510 Ms. The level of conductivity in the Rio Canete at RC-00 is an indicator of some contamination from waste waters and agricultural runoff. This is however, lower than that found at Herbay Bajo, where sewage would be expected to raise conductivity. Generally, agricultural runoff and sewage will increase conductivity due to the additional chloride, phosphate and nitrate ions. Nitrate levels recorded at RC-00b were also lower. Throughout the catchment nitrate levels ranged from ‘under range’ to 6.79mg/l NO3 perhaps underlining the limited extent of agriculture in the catchment.
At pH 8.55-8.79 the acidity of river waters is ideal for aquatic life and not approaching the tolerances of most aquatic vertebrates and invertebrates.

Site photos

Fig j  Site RC-00b  – looking down valley – showing braided channel bed with low water in main channel (Eustace Barnes
Fig j Site RC-00b – looking down valley – showing braided channel bed with low water in main channel (Eustace Barnes)
Fig 1k  Site RC00b – looking up valley – showing braided channel bed with low water in main channel.  (Eustace Barnes).
Fig 1k Site RC00b – looking up valley – showing braided channel bed with low water in main channel. (Eustace Barnes).
Fig 1l.RC-00b -Rio Canete estuary. Looking upstream, with Shrimp catching team by the river channel. (Eustace Barnes).
_Fig 1l.RC-00b -Rio Canete estuary. Looking upstream, with Shrimp catching team by the river channel. (Eustace Barnes). _
Fig 1m. Site RC00b.  (Eustace Barnes).
Fig 1m. Site RC00b. (Eustace Barnes).
Fig 1n  RC-00b. Female Cryphiops caementarius. Note that most specimens were female in the estuary (Eustace Barnes).
Fig 1n RC-00b. Female Cryphiops caementarius. Note that most specimens were female in the estuary (Eustace Barnes).
Fig 1o  RC-00b. The field team preparing specimens at RC-00b (Eustace Barnes
Fig 1o RC-00b. The field team preparing specimens at RC-00b (Eustace Barnes

Site description. Site RC00b is located below the Pan American highway below the city of Canete at sea level in the tropical zone. The Rio Canete, at this point is downriver of intensively farmed lands irrigated by waters extracted from the river at several points higher up. The town of Herbay Bajo is situated across the river and atop the river cliff on the south side of the channel. The valley at this point is a broad flat flood plain to the north bounded to the south by a steep river cliff. The channel flow is highly variable from the dry season to the wet season, depending on water abstraction for agriculture and urban demand from the various abstraction points. The channel itself is highly braided at this time and made up largely of gravel and smaller boulders. The river does hold water year-round. Discharge at the end of November is about 11.2 cubic meters per second but would be 15 cubic meters per second were no water taken out. During the wet season discharge is considerably higher. The banks are lined with river cane and scattered areas of stunted willow. Cultivated is intense at this elevation. The production of cotton, grapes, maize, ajo (garlic), aji (peppers), avocado dominates land use. There are smaller areas of sugar cane, a crop which dominates land use further north. There is little or no natural vegetation remaining in the lower valley and much of what was open desert has been irrigated and no highly productive agricultural lands. The water quality in the river at lower elevations is severely impacted by agricultural run-off and sewage disposal. The wider environment and fauna in the valley are largely determined by agriculture with many species expanding their range and abundance to occupy newly created agricultural lands. Desert fauna and flora has decreased accordingly. 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.

Fig 1p. Site RC00b.  (Eustace Barnes).
Fig 1p. Site RC00b. (Eustace Barnes).