The LOOP is an observational facility located in the Central Pyrenees, in the vicinities of the Aigüestortes i Estany de Sant Maurici National Park. It comprises a field station and several monitored catchments.  The research sites are equipped with several automatic weather stations, discharge gauge stations and lake and stream water temperature loggers. A network of sampling stations is visited to collect chemical and biological samples at different time intervals, from biweekly to seasonal. The sampling network consists of eight streams, fourteen lakes and two atmospheric deposition collectors for water chemistry, and four streams and one lake for biological sampling.

The most detailed limnological monitoring is carried out at Lake Redon, where the water column is sampled monthly at several depths for chemical and biological determinations. A small cabin with a lab, dormitory, and kitchen was set at the shore of the lake to facilitate the fieldwork and in situ experimentation.

In addition to the site-based monitoring, we carry out synoptic surveys covering the whole Pyrenean range at decadal intervals. This monitoring is aimed to compile long-term data series on the biochemistry of surface waters as an indicator of the relevant ecological processes taking place in the Pyrenean catchments and their response to global change. We also run short-term research projects which benefit from the framework of data, techniques, and facilities provided by the monitoring. Short-term projects include palaeolimnological studies that expand our data series many years back.  As a whole, all these activities configure our long-term ecological research programme.