Newsletter N°6

We are thrilled to invite you to DRYvER Final Event, happening on September 23 to 25, 2024 at INRAE Lyon and online. This exciting event will be filled with presentation of DRYvER results; presentations on intermittent rivers by experts from all over the world; discussions on the current gaps on the science and management of drying river networks; and on future research opportunities.

Event Details:

• Date: September 23 to 25
• Location: INRAE Lyon and Online
• Registration: Click on this link

DRYvER Final Event is the perfect opportunity to consolidate your scientific, socio-economic and management knowledge of non-perennial rivers and streams and their roles in river networks, meet professionals in this field from all over Europe and reflect on new European and national projects in this area. Whether you're a scientist, an academic, a NGO, a water agency, a policy maker; there's something for everyone.

Highlights Include:

• Margaret Shanafield, Flinders Univ. (Australia): Dry rivers in the Outback; what we do know and should learn about Australian rivers
• Amy Burgin, Univ. Of Kansas (USA): The Aquatic Intermittency Effects on Microbiomes in Streams (AIMS)
• Daniel Allen, Pennsylvania State Univ. (USA): StreamCLIMES: towards understanding how drying impacts streams across levels of biological organization and climates"
• Rachel Stubbington, Nottingham Trent Univ. (UK): Dry streams in a wet country: towards better protection of the biodiversity within England’s temporary chalk streams

Don't miss out on this event! Reserve your spot today and be part of an unforgettable experience. For more information and to register, visit DRYvER Website!

We look forward to seeing you there!

Coming soon

This is the title of the article recently published in Limnology and Oceanography letters (DOI: 10.1002/lol2.10408) by Naiara López-Rojo and colleagues, with in the work package dedicated to the analysis of the effect of drying on ecosystem functioning. Drying can impair many C-related ecosystem functions as non-perennial rivers (NPRs) support a temporally dynamic mosaic of different habitats (flowing water, dry riverbeds and isolated pools), determined by drying and rewetting events. However, current global estimates from inland waters are based exclusively on data from perennial reaches (PRs).

GHG emissions happen from flowing water and dry riverbed as main habitats. Total reach emissions can result purely from flowing waters, from flowing water and dry riverbed during flow contraction or only from dry riverbeds when there is no surface water in NPRs

In this study, they quantified in situ CO2 and CH4 emissions from flowing waters and dry riverbeds in the 6 European focal drying river networks - DRNs (Croatia, Czech Republic, Finland, France, Hungary and Spain, 20 sampling sites on each, including PR and NPR reaches) and 3 sampling campaigns in 2021 (spring, summer, autumn-winter). They also characterised the local abiotic conditions (water physico-chemistry, sediment characteristics…) and extracted different metrics characterising land uses in the draining catchment and climatic conditions and calculated several metrics describing drying regime and river network fragmentation. This unique dataset enabled to determine the drivers of C emissions from dry riverbeds, and for PR and NPR flowing waters. The drivers of CO2 and CH4 emissions differed between PR and NPR reaches, indicating the “drying legacy” effect from NPR flowing water, even long after flow resumption.

When upscaling the CO2 emissions from the sampling points to the whole river networks, for all year 2021, they found that the annual contribution of dry riverbeds exceeded 50% in three of the 6 case studies: even in the boreal and most perennial DRN (Lepsämänjoki, Finland), incorporating the contribution of dry riverbeds led to a 14% increase of annual emissions.

At the annual scale, emissions from dry riverbeds represented 14% of total emissions in the Finnish DRN and >50% in the Spanish one

The results of this study indicate that current estimates of global C emissions from streams and rivers are substantially underestimated, as both surfaces of dry riverbeds of PRs and NPRs and dry periods of NPRs were considered as negligible. The results of our study highlight the unique functioning of NPR rivers and call for an urgent need to include them in global estimates of greenhouse gas emissions.

Thanks to the organisation by Professor Carla Rezende, members of WP4 & 5 across Europe and CELAC countries, together with the wider academic community of Universidade Federal do Ceará, participated in a two-week knowledge exchange programme in Brazil, from the 22nd April to 3rd May. This involved scientific exchange and various stakeholder and community workshops.

José Carlos Araújo provided an overview of drying rivers in Ceará. He explained that high evaporation rates are the primary cause of drying. The study area has a dense network of small reservoirs to provide water during drought periods, and the local government has implemented measures such as rain cisterns to supply drinking water to the community. The drying problem has severely impacted local daily lives.

Caatinga is a unique dry tropical savanna ecosystem located in northeastern Brazil. The term originates from the Tupi language, meaning "white forest", named for its appearance during the dry season when the trees lose their leaves, exposing their white trunks.

Francisca Soares de Araújo introduced the phytogeography of the Caatinga region. She highlighted the unique vegetation system and its interaction with the environment, offering insights into the distinct characteristics of the local flora and the ecological dynamics in the Caatinga.

Picture: participants of the GA in the campus of Universidade Federal do Ceará

Carla Rezende presented recent work focusing on the study of regional biodiversity. Through showcasing patterns in diversity of local fish, insects, and amphibians, Carla illustrated the uniqueness of the river network and explained the impact of both the dry and rainy seasons.

Gabriel Nuto Nobrega introduced upcoming policies aimed at encouraging and promoting environmental conservation. This policy focuses on the Payment for Environmental Services and aligns with the recent experiences from the Ceará State and the Environmental and Climate Change Secretary. The policy aims to provide financial instruments for the provision of ecosystem services. It seeks to reduce poverty and promote social inclusion.

Pedro Medeiros introduced his work on natural based solutions in the region. Carlos Alexandre Gomes Costa presented his recent publication on the recovery of degraded areas in the riparian zone of intermittent rivers.

Julia Martin Ortega gave a lecture on the monetary valuation of ecosystem services, with the definition of ecosystem services and the general methods of valuation via revealed preference and stated preference. Jingyuan Di and Enni Ruokamo presented the preliminary results of the surveys conducted in the Genal River in Spain and the Lepsamanjoki River in Finland as part of the DRYvER project.

Profesor José Carlos Araújo commented:
The method (choice experiment) was employed by the Brazilian government to evaluate water quality and could contribute to a wider field of research.

Lisette de Senerpont Domis explained adaptive management of drying river networks and ahd an interactive session on operationalizing the nature futures framework of the IPBES. This approach invites stakeholders to express their understanding and attitudes toward the environment. Eerika Albrecht explained the analysis of EU policy and governance, and Polona Pengal delivered an online session on the implementation of natural based solutions. Nabor Moya introduced the case study of the Upper River Chico Basin in Bolivia.

Fun fact: The DRYvER members were interviewed when walking in the city of Taua and the Instagram post was liked 1,500 times.

Picture: Evening twilight at Tauá, Ceará

A stakeholder workshop was held in Aiuaba. More than 60 members of the community, including representatives of various environmental and water management sectors and local authorities attended. The group was welcomed by a brass band, a first in all the co-creation workshops sofar. The workshop used DRYvER’s approach to stakeholder engagement to discuss desirable futures in the context of drying river networks, using the IPBES Natures Futures Framework.

Picture: participants of the Aiuaba workshop

The event highlighted the significance of the bottom-up method, emphasizing the power of local people and the synergy between public initiatives and academic research. It became clear that engaging local communities is crucial for the success of environmental projects, as they possess invaluable firsthand knowledge and a deep connection to their surroundings.

Picture: public engagement of the meeting in Aiuaba

The discussions underscored the fact that rivers, while sharing certain characteristics, also exhibit unique differences. The factors contributing to their drying up are not uniform across different regions, which means that a one-size-fits-all approach to intervention is inadequate. Each river has its own set of challenges and requires tailored strategies that consider its specific ecological, social, and economic context.

Overall, the event reinforced the idea that sustainable environmental management hinges on the integration of local knowledge with scientific research, and the recognition of the unique attributes of each river system. By fostering this comprehensive and inclusive approach, we can better tackle the complex environmental challenges we face today.

During the last month, WP1 has made significant strides in understanding and predicting flow intermittence in river networks across Europe. The teams have developed novel modeling approaches to predict flow intermittence at both the regional scale within the six pilot DRNs and at the continental scale in Europe, resulting in two published papers.

In their paper “Flow intermittence prediction using a hybrid hydrological modelling approach: influence of observed intermittence data on the training of a random forest model,” Mimeau et al. (2024; 10.5194/hess-28-851-2024) published their approach to combining physically-based models with random forest techniques, offering a robust method to predict where and when rivers might dry up.

By leveraging high-resolution data, the authors provide detailed insights into local drying trends and project future changes using an ensemble of climate models. As a joint effort of all WPs, indicators were developed, which are currently being used to prepare another paper on future projections of flow intermittence in European DRNs.

Additionally, to present the results of drying patterns, an online application was developed (Figure 1). This app allows users to explore the evolution of flow intermittence patterns in time and space within the studied European river networks under past-present climate conditions (1960-2021) and climate change projections until 2100. The DRYvER Hydro web app is available to the public at: https://www.dryver.eu/results/interactive-applications

In a second paper, published as a preprint, “Streamflow intermittence in Europe: Estimating high-resolution monthly time series by downscaling of simulated runoff and Random Forest modeling,” Döll et al. (2023; 10.22541/essoar.170317298.88189056/v1) presented their methodology for modeling drying patterns at the continental scale. They found that 3.8 % of all European reach-months and 17.2 % of all reaches were non-perennial during 1981-2019, predominantly with 30-31 no flow days. A paper on the impacts of climate change on streamflow intermittence in Europe is currently in preparation.

Figure: DRYvER Hydro, which displays the results of flow intermittence modelling in the 6 studied river networks: Albarine (France), Bükkösdi (Hungary), Butižnica (Croatia), Genal (Spain), Lepsämänjoki (Finland), and Velička (Czech Republic)

Climate change poses a significant threat to river ecosystems. Alterations in river discharge and the increased frequency and duration of drying events can impact the structure and functioning of aquatic communities. Predicting these communities' responses to potential climate change scenarios is crucial. However, many biodiversity projections fail to consider how shifts in hydrological regimes mediate the response of river biological communities to climate change.

To address this, the DRYVER project has studied six drying river networks (DRNs) with varied climate and hydrological conditions. Extensive research and modeling of these networks' hydrology allow us to predict changes in river discharge, drying frequency, and duration across fifteen climate change scenarios.

The project also sampled aquatic macroinvertebrates, biofilm bacteria, and sediment bacteria across different river segments and times of the year to characterize river biodiversity responses. Using machine learning, we analyze this data to predict changes in community features such as species richness, taxonomic diversity, functional diversity, and total abundance in relation to river characteristics (channel depth, width, elevation, climate) and hydrological regimes (discharge, drying frequency, drying duration). Coupled with hydrological models, this approach enables us to forecast changes in drying river biodiversity under various climate change pathways.

Our findings indicate that macroinvertebrate and biofilm bacteria communities exhibit the most significant shifts under high emission scenarios compared to low emission scenarios (Figure 1). The Bükkösdi river network in Hungary is predicted to experience the most substantial biological community shifts. Macroinvertebrate diversity decreases in most river segments across all DRNs, primarily due to a decline in Ephemeroptera, Plecoptera, and Trichoptera (EPT) species, partially offset by an increase in Odonata, Coleoptera, and Hemiptera (OCH) species diversity (Figure 2). The main drivers of this decline are increased drying frequency and decreased river discharge. This trend suggests a shift from species-rich lotic (flowing water) communities to species-poor lentic (standing water) communities adapted to increasing drying.

Biofilm bacteria communities, and to a lesser extent sediment bacteria communities, show a marked increase in diversity under high emission scenarios (Figure 1). Detailed results indicate that this is due to the coexistence of bacteria typical of dry and wet river conditions in biofilms and sediments. Current research aims to determine the metabolic signature of these intermediate bacterial communities so that we can link them to the variation of river greenhouse gas emissions with drying (see Naiara López-Rojo work, newsletter #4).

In conclusion, our work demonstrates how changes in increasing drying in the future will affect the diversity and structure of biological communities in Europe. We highlight the significant impact of socio-economic decisions regarding greenhouse gas emissions on river biodiversity, which in turn may affect the overall functioning of river ecosystems.

Figure 1. Differences in river segment diversity (diversity anomaly) between the periods (2090 - 2100) and (2016 - 2026) according to high emission climate change scenarios SSP1-RCP2.6 and SSP5-RCP8.5

Figure 2. Zoom on macroinvertebrate communities. From left to right in each panel, difference in river segment diversity (diversity anomaly) of (i) the whole macroinvertebrate communities, the (ii) Ephemeroptera, Plecoptera, Trichoptera functional group and the (iii) Odonata, Hemiptera, Coleoptera functional group between the periods (2090 - 2100) and (2016 - 2026), and according to low emission climate change scenario (SSP1-RCP2.6, left panel) and high emission climate change scenario SSP5-RCP8.5 (right panel).

Rivers are biodiversity hotspots and provide essential ecosystem services and functions, including provision of drinking water, food, climate regulation among others that are vital for human wellbeing. All river networks are composed of perennial and nonperennial river segments. Non-perennial river segments can be naturally intermittent due to climatic, geological or hydrogeologic causes, whereas more and more once-perennial rivers are drying due to human water uses, such as abstraction, river damming or land use alterations. Non-perennial river segments are only rarely considered as their own river type in Water Framework Directive, where ecological status of a water body is assessed through comparison of biological quality elements with reference conditions. Ongoing climate change further increases the risks of drying and may lead to declines in species diversity and irreversible shifts in the composition of communities across river networks. This necessitates adaptive management to safeguard biodiversity and ecosystem functions and services in the river networks. DRYvER project recommends that legal frameworks should be adaptive towards the scientific evidence provided on the changing habitats. Non-perennial parts should be considered as integral part of the river network. Non-perennial river segments could be recognized as a water body including their definition by the Water Framework Directive and its implementation strategy. The cause of drying should also be clearly identified to define types of non-perennial river segments. DRNs should be protected and restored in accordance with the EU Biodiversity Strategy objectives and other relevant legislation, such as the Habitats Directive and Restoration Law to safeguard multiple ecological functions provided by the river networks.

DRYvER thanks all positively voting members of our European policy-deciding community (especially the Commission, the Parliament and the Council) and recognises the effort of many organisations to adopt the NRL. The law puts legally binding targets on ambitions, which have been discussed for a long in policy and are largely based on scientific evidence, even if there are concerns about the degree of ambition. The NRL establishes that to turn at least 25,000 km of rivers into free-flowing rivers by 2030, member states will take measures to remove man-made barriers to the connectivity of surface waters. The results produced by DRYvER on the fragmentation of river networks by drying and its effect on the ecological integrity of river networks are very relevant here.

The regulation requires member states to establish and implement measures to jointly restore, as an EU target, at least 20% of the EU’s land and sea areas by 2030, and it covers a range of terrestrial, coastal and freshwater, forest, agricultural and urban ecosystems, including wetlands, grasslands, forests, rivers and lakes, as well as marine ecosystems, such as seagrass and sponge and coral beds. On habitats deemed in poor condition, as listed in the regulation, member states will take measures to restore at least 30% by 2030, with further targets for later deadlines. The adoption of the Law and the subsequent National Restoration Plans are a welcome opportunity to avoid the further deterioration of water bodies and ecosystems; a goal which also DRYvER aims to contribute to. More information at: https://environment.ec.europa.eu/topics/nature-and-biodiversity/nature-restoration-law_en