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Quantifying ecological effects of small hydropower in Alpine stream ecosystems

Periodic Reporting for period 1 - SHYDRO-ALP (Quantifying ecological effects of small hydropower in Alpine stream ecosystems)

Reporting period: 2017-05-01 to 2019-04-30

Among the sources of sustainable energy, hydropower (HP) production is booming globally, with expected rate of increase particularly high in Alpine regions. However, while the production of renewable energy from HP is rightly supported, such development must meet ecological criteria.
The challenge is how to maintain hydropower production while reducing its negative impacts on the environment. To achieve this, a clear understanding of the relation between hydrologic regimes and riverine biodiversity is necessary. Using the Adige River basin (IT) as a rappresentative Alpine case-study, the key issues being address in the project are therefore:

i) quantifying the relation between river flow characteristics and aquatic invertebrate communities;
ii) assessing the extent to which current bio-indicators used to evaluate ecosystem integrity respond to river flow characteristics;
iii) seek novel ecological / biological metrics that are sensitive to river flow alterations (e.g. due to hydropower facilities).

This is a very timely topic, considering the accelerating pace with which global climate is changing and biodiversity is being eroded. The issue of balancing the production of hydropower and the maintenance of ecological integrity is particularly relevant in the Alpine area where hundreds of new small-hydropower facilities are planned or under construction.

The main conclusions of the project are that:
- The Adige River has lost most of its natural continuity and ecological connectivity due to not only hydropower facilities but also in-stream obstacles.
- The current biological indicator based on aquatic invertebrates appears rather insensitive to flow alteration, while responding mostly to water quality.
- Novel bio-indicators specifically designed to reflect hydrological conditions of rivers are needed.
"Using river monitoring data from the Environmental Protection Agencies of Trento and Bolzano, a set of novel statistical analyses were performed to quantify the relation between river biodiversity and river flow characteristics in the Adige River basin (IT).

The first effort provided results regarding the sensitivity of the official bio-indicators to river flow. The data suggest that aquatic invertebrates respond to water quality and only marginally to geo-morphological and flow-related alterations. However, poor ecological conditions were observed where the alteration of river flow was stronger. This suggest that the effects of flow alterations are evident, but only where such alterations are severe.
In a second analysis, a geo-spatial approach was used to assess the spatial patterns in the distribution of biodiversity along the Adige River. The aim was to understand whether biodiversity data could provide insight into the longitudinal connectivity of the river network. Substantial discontinuities in the longitudinal distribution of key aquatic invertebrate groups were observed, suggesting that the longitudinal continuity in the Adige River network has been markedly altered.
In a later stage, a collaboration with hydrologists from the University of Trento, led the development of a large dataset where the 'natural' flow regime of 100 sites across the Adige River was simulated. This allowed us to create the first classification of flow-types in the basin.

Field work included the collection of water quality and invertebrate data from a set of locations up- and down-stream of small hydropower facilities. A total of eight streams were selected based on site accessibility and information on hydropower plants.
Field experiments were conducted in semi-artificial flumes nearby the Fersina stream. The experiments simulated the effects of small water withdrawal on benthic invertebrates. The flumes were naturally colonised by benthic invertebrates from the Fersina stream that feeds the flumes from upstream. Before the start of the experiment, the flumes were virtually divided in two halves. The upstream half served as control, while water was withdrawn from the downstream half (using valves) to simulate the effect of SHP operation. We used a before-after - control-impact (BACI) design with three sampling dates. ‘Sample 0’ was taken initially as control, with no water regulation. Then, water flow was decreased by 50% in the downstream half of each flume. After one week of treatment, ‘Sample 1’ and 'Sample 2"" were collected after 1 week and 2 weeks, respectively. Each sample consisted of three replicate baskets taken from each control and treatment. A total of 54 baskets were collected.

Data from the field-work and the experiments are currently being processed. This involves a long process of sorting and identification of the organisms using microscopes.

The project was presented to a wide audience including both technical and non-technical targets. The results were discussed with academic audience at the International Society for River Science meeting in Hamilton (NZ), and to the Eco-Hydraulic conference in Trento. These included an audience with expertise in ecological and hydrological sciences. Dissemination to a non-academic audience involved the participation to the 'Notte dei Ricercatori' at the MUSE and a workshop for students within the Euroflow project. The project was also presented at a stakeholder meeting in Bologna, which included practitioners involved in river restoration.
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"Understanding the relation between the characteristics of river flow and its biodiversity is an active area of research in ecology, known as ""flow-ecology relationship"". A sound understanding of the link between river discharge and its ecology is needed for achieving the sustainable management of water resources. However, most understanding of 'flow-ecology relationship' is based on studies on fish populations, while little is known about the response of other groups. Moreover, studies that specifically focused on Alpine streams and rivers are also scarce.

This project and its results provide a valid contribution to this area of research by:

i) Providing a quantitative description of the link between different aspects of river flow and invertebrate communities, across a large Alpine river.
ii) Addressing the limits of current official ecological metrics as indicators of river flow.
iii) Proposing a novel method to quantify the longitudinal continuity of ecosystem attributes over the entire river network.
iv) Generating one of the first classifications of natural river-flow regimes in an Alpine basin, which could serve as first step for the assessment of hydrologic alterations.

These results can help setting environmental flows (E-flows) in the area. Environmental flows define the quantity of flowing water that a stream must maintain in order to sustain a healthy ecosystem. Setting the right targets regarding E-flows has practical implications for the management of renewable energy, and important societal consequences. Healthy streams and rivers provide a wealth of ecosystem services including clean water provision, flood protection, and recreational values that benefit citizens of all ages.
Safeguarding the ecological integrity of rivers while maximising their potential as 'clean' energy providers requires the collaboration of different sectors. Results from this project could serve future efforts to achieve this goal in the Alpine area and beyond."