Campaign #3

On Tuesday 30 January, we headed out to the field for the first day of the third campaign. The experiences of the first two campaigns came in handy to access the selected sampling sites and organise the logistics of the field visits. The extreme drought of the previous campaign has had a clear impact on the water levels in the reservoirs, which still seemed to be about 15 meters below their normal level. In the end, 52 accessible sites were selected: 31 river/stream sites and 21 reservoir sites.

We collected information on the abiotic conditions in each of the 52 sampling sites. To get this data, we made use of a multiprobe (a device that measures several conditions at once) on-site and USEPA approved test kits to determine the nutrient concentrations off-site. The collection of this data confirmed the patterns of the first campaign and are in line with what we expected. For instance, nutrient concentrations were the lowest in the upstream locations and highest directly downstream of the city of Cuenca. On the other hand, oxygen levels showed a more constant pattern. This does not come as a great surprise, considering the relatively high flow velocities and turbulent character of the sampling sites that allow for an efficient oxygen exchange with the atmosphere.

In addition to the more standard abiotic conditions, we also collected information on the presence and the emission of greenhouse gases in each of the 52 sampling sites. To get this data, we made use of a the headspace method (mixing 30 mL of water and 30 mL of air) and floating chambers (airtight containers sampled at fixed time intervals) on-site followed by the analysis of the obtained samples off-site. This data already resulted in some interesting patterns that are in line with both previous campaigns and the abiotic conditions. For instance, methane concentrations and emissions were the highest in the upstream part of the Amaluza reservoir that is almost completely covered by water hyacinth (site AM03), which also showed a low oxygen level and relatively high nutrient levels. Similarly, the most upstream site within the Mazar reservoir (site MA04, due to reduced water levels) displays a high emission of methane, while having a lower oxygen level and higher nutrient levels compared to the other reservoir sites.

A total of 52 sampling sites were selected and assessed for a variety of water quality parameters. The abiotic conditions showed a clear similarity with the first campaign, with extremely high nutrient levels directly downstream of the city of Cuenca. The greenhouse gases showed a similar pattern as well, though this is partially masked by the high values for a small set of reservoir sites.

More information can be found in the short report on the third sampling campaign [link].

We would like to thank C.X. Lopez Solis and K.P. Ramirez Pozo for their help in collecting the samples in the field as well as their subsequent processing in the lab. We also thank D.G. Zuñiga Villegas for providing us with the necessary transport.