Flow regulation by dams impacts more than land use on water quality and benthic communities in high-gradient streams in a semi-arid region

CALDERON MIRIAN; CESAR AMERICO ALMEIDA; MARIANA BEATRIZ JOFRE; SILVIA PATRICIA GONZALEZ; MISERENDINO MARIA LAURA

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2023

0048-9697

In semi-arid regions, water policy has strongly promoted the construction of water reservoirs with little or no consid- eration for their ecological consequences. In order to quantify the effect induced by flowdiscontinuity on environmen- tal conditions, water quality, and invertebrate communities at high-gradient streams, we investigated unregulated and regulated reaches at 13 watercourses, located in the Dry Chaco Ecoregion (South America). Dams differed in the dom- inant land uses (rangeland, agriculture, and urban) of the related catchment area. We assessed on-site hydro- geomorphic features, water quality and bacteriological parameters, habitat condition, chlorophyll a, macrophytes cover, and macroinvertebrate communities. Significant increases in mineral parameters and organic contamination in- dicators were detected at regulated reaches, such as: conductivity, total solids, turbidity, color, and phosphates. Dams negatively affected habitat condition, andmacrophyte cover increased at regulated sites. Macroinvertebrates showed a diminution in most of the metrics analyzed, with a decrease of sensitive groups and an increase in the more tolerant ones. Redundancy Analysis revealed that SWQI (physicochemical based index) and the proportion of coarse gravel were stronger predictors on metrics arrangement. Variance partitioning analyses proved that regulation effects prevailed over land use in explaining metrics variation. Invertebrate community was positively related to better eco- logical conditions, which suggests that restitution of ecological integrity at regulated reaches should include habitat restoration. These results are relevant for the management of regulated water resources in arid and semi-arid regions in a context of climate change.