Watercourse monitoring network

Biodiversity in watercourses is monitored in two stages: Firstly, all aquatic invertebrates are collected and identified at family level. Specialists then identify the larvae of three selected insect orders – mayflies, stoneflies and caddisflies – down to the species level, as far as possible.



Monitoring the aquatic fauna means getting wet: Equipped with fishing boots, field workers wade through the water of smaller rivers and streams along a precisely defined section. The sediment is stirred up at several points and collected with a standard dip net, after which all of the aquatic invertebrates are separated out and identified at family level. This can be used to calculate various water quality indices.

This methodology is in line with the widely used modular step-by-step concept for macrozoobenthos – see box opposite. The larvae of the three insect orders mayflies, stoneflies and caddisflies are collected and identified down to species level in the laboratory by specialists. In addition, information on ecomorphology and water quality is also recorded at a measuring point, which provides further information for analysis.

Measuring point


The measuring point in a watercourse is shown in blue. The length of the section may vary depending on the situation.

Monitoring network


The monitoring network for surveying the diversity of aquatic insects comprises around 500 sections of around 5 to 100 metres in length in smaller watercourses. 

Step by step

This photo series follows a BDM employee as she takes samples from a stream in the watercourse monitoring network. Click on the pictures for a larger view.

  • The photo shows a mountain stream.
    One of roughly 500 BDM stonefly, caddisfly and mayfly sampling sites by a small Swiss watercourse.
  • The biologist measures the width of a mountain stream with a measuring tape.
    The BDM fieldworker records the watercourse section’s position, length and width.
  • The biologist stands in fishing boots in the torrential water of the mountain stream and takes a sample from the bottom of the water with a special landing net.
    In a spot defined by the monitoring method, she places a net in the watercourse, stirring up the stream bed with her boot. As a result, insect larvae are washed into the net.
  • The field worker wipes over stones with her left hand while holding the landing net in her right hand to catch the organisms that have been released.
    Large rocks in the stream make it possible to collect critters by hand.
  • The biologist sits on the ground, with two plastic bowls and various small containers spread out in front of her, into which she packs the catch with the help of tweezers.
    Back on land, she eliminates pebbles and bycatch, carefully picking the tiny invertebrates.
  • The water in the plastic bowl is carefully poured over a corner into a sieve, leaving the gravel behind.
    Eventually, the fieldworker sieves through the remaining material in order to catch any remaining larvae.
  • A close-up of the plastic trays and the small boxes filled with catches.
    Full sample containers ready for transport.
  • One of the species specialists identifies the larvae of the river insects in a Petri dish under the binoculars.
    Later, specialists sort and analyse the aquatic invertebrates in the laboratory.

Methodology guides

The methodology for the field and laboratory work is described in detail to ensure a standardised procedure. The corresponding methodology documents are publicly accessible.

Monitoring networks at a glance

Find a descriptive overview of the BDM monitoring networks online.

Landscapes monitoring network

Field workers record the plants, butterflies and breeding birds over an area of one square kilometre. They generally follow a precisely defined route along paths and roads.

Terrestrial habitats monitoring network

Field workers monitor the selected species groups over a circular area of 10 square metres. They collect the vascular plants directly on-site. They take samples of moss types and snails for analysis in specialised laboratories.

Modular stepwise procedure

The Modular Stepwise Procedure (MSP) is a collection of methods for monitoring and assessing the status of water bodies in Switzerland. It is the result of a cooperation between the federal government, the cantons, Eawag and the VSA.