The joint monitoring protocol for high-altitude lakes takes into account the difficulties involved in site access, the field officers' limited time, and the need to reduce costs as much as possible. It is therefore based on:
- an annual on-site campaign,
- optimised sample material,
- flexible return time for samples
- low analysis costs for samples taken.
The samples and measurements are taken from a point in line with the deepest part of the lake, identified by GPS, and marked by a permanent chain of thermistors (high-frequency temperature sensors).
These on-site missions take place in September (at the end of the stratification period and the peak of primary production) and involve at least three people as the equipment (including the boat, paddle, rope, probe, etc.) has to be carried in most situations.
The stakeholders working in the Observatory must respect a charter for the implementation of monitoring protocols in order to ensure homogeneity in the data collected.
As a long-term monitoring programme, network discussions help to regularly evaluate the relevance of the measurements carried out and, potentially, to make changes in the joint protocol depending on the knowledge gained and defined needs.
The joint protocol proposes the implementation of permanent temperature sensors, multiparameter probe profiles and, for some lakes, limited sampling of the body of water (plankton and fish). The parameters can be classified according to two categories:
- "Mandatory" parameters
- "Optional" parameters
At least three parameters are carried out on each of the Observatory's lakes:
- water transparency,
- development of a multiparameter probe profile (pH, temperature, conductivity and dissolved oxygen) across the entirety of the water column,
- temperature readings from thermistors (data-loggers), placed at the bottom of the lake and beneath the surface of the water, along a fixed, submerged chain.
These parameters, which are easy to implement and do not require a lot of equipment, provide information about:
- the annual transparency of the lake and its physico-chemical state,
- continuous temperature changes in the column of water.
For some lakes, complementary samples and measurements are carried out in order to study other compartments of the ecosystem (chemical analysis, phytoplankton, zooplankton, chlorophyll a, fish, etc.) in a more precise way.
Today, these monitoring parameters are optional because they require more time to implement and a recurring cost for analysing the samples.