Abundances of benthic invertebrates and related environmental variables over a 5-year sampling period in a glacier-fed stream used for hydropower generation (South Tyrol, Italy)

Stream benthic macroinvertebrates have been collected for a period of 5 consecutive years, twice a year (2015-2019, in April/May and in September/October), along a longitudinal transect of the Saldur stream, a near pristine glacier-fed stream located in South Tyrol, Italy (46°N, 10° E), part of the International Long Term Ecological Research (ILTER) network (site code: IT-25, LTER_EU_IT_100). From year 2016 on, a small "run-of-river" (ROR) hydropower plant (max. 3,200 kW/year) started to operate on the stream, and the sampling sites were chosen accordingly, to examine its potential impact on the riverine ecosystem.

Organisms were collected through Surber samplings (0.0506 squared metres, mesh size 500 µm) in 6 sites at different elevation and distance from the glacial source and from the weir of the hydropower plant: Saldur_1 (2,030 m a.s.l.; 4.962 km from glacial source; ~1 km upstream of the weir ), Saldur_2A (2,016 m a.s.l.; 5.225 km from glacial source; ~100 m upstream of the weir), Saldur_2B (2,006 m a.s.l.; 5.325 km from glacial source; located in the river stretch between the weir and the outlet pipe of the two sediment traps of the ROR hydropower plant, so ~ 100 m downstream of the weir); Saldur_2C (1,997 m a.s.l.; 5.486 km from the glacial source; ~50 m downstream of the above mentioned outlet pipe and ~ 150 m downstream of site 2B); Saldur_2D (1,779 m a.s.l.; 8.217 km from the glacial source; ~ 3,000 m downstream of the weir); Saldur_3 (1,645 m a.s.l.; 11.123 km from the glacial source; ~ 6,000 m downstream of the weir).