Campaign #4

On Monday 06 May, we headed out to the field for the first day of the fourth campaign. The experiences of the first three campaigns came in handy to access the selected sampling sites and organise the logistics of the field visits. The extreme drought of the previous months 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, 53 accessible sites were selected: 32 river/stream sites and 21 reservoir sites.

We collected information on the abiotic conditions in each of the 53 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. Similarly, conductivity levels showed the influence of the city of Cuenca on the river water quality: the highest conductivity levels were observed directly downstream of the city.

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 53 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 previous campaigns. For instance, carbon dioxide concentrations and emissions were the lowest in the upstream part of the Paute basin (and even suggesting a local sink function at site TO18) and highest directly downstream of the city of Cuenca (site CU03, displaying the highest concentration) and close to the dam in the Mazar reservoir (site MA11, displaying the highest emission). In addition, also the Amaluza reservoir seems to be relevant in the story surrounding the greenhouse gases, displaying relatively high concentration and emission levels in site AM06.

A total of 53 sampling sites were selected and assessed for a variety of water quality parameters. The abiotic conditions showed a clear similarity with the previous campaigns, with clearly higher nutrient levels directly downstream of the city of Cuenca. Emissions of carbon dioxide are clearly higher in the downstream part of the reservoir, while some sites even act as a carbon dioxide sink rather than source.

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

We would like to thank D.J. Vimos Lojano 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.