Running waters

Running Waters

South Tyrol is rich in water. Every year, large amounts of rain and snow fall on the region. A large proportion flows across the surface, forming streams and rivers. As part of our biodiversity monitoring program, we study 120 freshwater sites over a four-year period. Each year, 24 control sites and an additional 24 sites are examined. We focus on surveying the larvae of various aquatic insects such as caddisflies and mayflies. In addition, we also investigate abiotic water parameters such as, pH value, conductivity, oxygen and various nutrient conctrations of the respective streams.

South Tyrol’s streams and rivers are characterized by highly divers topographical, geological and climatic conditions. For the biodiversity monitoring, all streams were therefore classified into categories that differ in terms of altitude, discharge and geology.

Ditches and slow-flowing streams on the valley floor are characteristic of the colline zone. Channelised streams, such as ditches in the lowlands, are mainly used for drainage and irrigation and as receiving waters for treated wastewater from the large sewage treatment plants. As these watercourses are often located close to agricultural land, such as intensively used orchards or vineyards, diffuse sources of pollution from agriculture can affect the stream organisms living in them.

These watercourses are often located in the immediate vicinity of agricultural land, such as intensively used orchards or vineyards

Typical vegetation of a ditch

The survey of the ditches begins quite early in the field season, with the team usually out and about as early as March

Canalized watercourses are mainly used for drainage and irrigation and as receiving waters for treated wastewater from the large sewage treatment plants

Montane streams and riversrefer to running waters within the montane zone, characterized by low, medium and high discharge, as well as medium and steep slopes. Depending on the region, the geomorphology differs between silicate and carbonate. The substrates and so-called microhabitats can be very different: for example, behind fallen tree trunks, sandbanks and fine sediment may accumulate, while in shallow, fast-flowing sections, gravel and big sediments dominate. In addition, the water depth varies considerably locally. The montane/silicate streams in particular can be intermittent (temporary). The species communities in montane streams can therefore vary greatly depending on the characteristics of the stream sections under investigation. Sensitive groups such as mayfly, stonefly and caddisfly larvae are mainly found here.

The typology, montane streams, represents watercourses within the montane zone, characterized by low, medium or high discharge, and moderate to steep slopes

Gravel and big sediments can be found in shallow, fast-flowing sections. Such a section is surveyed in the picture

The substrates and so-called microhabitats can be very different

In montane streams we find mainly sensitive groups such as mayfly, stonefly and caddisfly larvae. In the picture: stonefly larvae

Alpine streams are strongly influenced by climatic conditions in the Alps, where high altitudes cause winter precipitation to fall as ice and snow. The snow melts comparatively late, which leads to increased water levels in the summer months. The generally low water temperature, the high oxygen content and the presence of coarse substrates such as stones and boulders characterize alpine streams. These characteristics support diverse and specialized macroinvertebrate communities as as some species are highly adapted to alpine stream conditions.

The generally low water temperature, the high oxygen content are typical for alpine rivers

The presence of coarse substrates such as stones and boulders characterize alpine streams

The special characteristics of alpine streams mean that the macroinvertebrate communities here are very species-rich and need very specific habitats. In the picture: Mayfly larvae

Alpine streams are strongly influenced by climatic conditions in the Alps

Glacial streams are characterized by varying, sometimes high discharge, low water temperatures throughout the year, high levels of suspended fine sediments and low nutrient concentrations. These special conditions limit the occurrence of macroinvertebrates, with species communities characterized by a number of specialists.

Survey in a glacial stream

Specific conditions prevail here: highly variable discharge, especially in summer, low water temperatures throughout the year, low nutrient concentrations, and a high amount of fine sediments