Temporary Rivers & Streams Meeting

James White, RRC

On Tuesday 21st June, I represented the RRC at the 7th annual ‘Temporary Rivers & Streams Meeting’ organised by Prof. Rachel Stubbington (Nottingham Trent University) and Dr Judy England (Environment Agency). This annual meeting aims to unite academic and practitioner scientists globally undertaking research or management actions on temporary rivers and streams – i.e. watercourses ceasing to flow periodically.

After the organisers introduced the meeting to in-person and online attendees, CEH’s Cath Sefton chaired the morning session on mapping temporary rivers and streams, and organic material within them (i.e. leaves). The first three speakers in this session are based at the National Research Institute for Agriculture, Food and Environment (INRAE) in Lyon, France. Mathis Messager opened the session by discussing his modelling approach to characterising the prevalence of temporary rivers and streams globally (see image below), as there remains a poor understanding on the distribution of such systems. His findings indicate that 51–60% of rivers worldwide cease flowing for at least 1 day annually, and these temporary watercourses occur across various continents and biomes. Romain Sarremejane then presented his research assessing river network characteristics and intermittency patterns on leaf litter quantities and decomposition alongside invertebrate communities. Amélie Truchy then presented the DRYvER app (see https://www.dryver.eu/), whereby citizen scientists worldwide can upload observations of flow intermittency to help map the distribution of temporary rivers and streams – with over 800 users already inputting data! Natural England’s Chris Mainstone wrapped up the session by presenting ‘priority habitat’ work being undertaken across the UK, with a specific emphasis on better incorporating and targeting smaller, temporary rivers and streams.

Global distribution of temporary rivers incorporated in Mathis Messager’s presentation at the temporary river workshop (also Fig. 1 in Messager et al., 2021. pp. 392).

After the French contingent had a further chance to answer questions on their research over a short coffee break, Chloe Hayes (Nottingham Trent University) and Richard Handley (Environment Agency) chaired a session on the monitoring, management and restoration of temporary rivers and streams. Chloe presented findings from her PhD examining the role of terrestrial plants and invertebrates as bioindicators of ecosystem health in English winterbournes (chalk rivers and streams that dry during the summer and flow in the winter). She discussed how such information could inform biomonitoring in temporary streams and rivers, which are severely lacking in such environments relative to their perennial counterparts. Huddersfield University’s Tory Milner then presented her research on macrophyte colonisation of dry channels in the karstic, limestone rivers of the Peak District, presenting key insights on how such flora disperse in such systems. The following two papers were presented by Nottingham Trent University representatives, with Kieran Gething firstly highlighting his PhD results which indicate that nationally rare, temporary water invertebrate specialists (see below) may be more common than we think. Jamal Kabir then presented various measures of conservation value that indicate the biodiversity of headwater springs and streams on the chalk South Downs. The Environment Agency’s John Murray Bligh then concluded the session by discussing the ‘River Surveillance Network’, an initiative that is being adapted to include various sources of information (e.g., ecological) across temporary rivers and streams.

Rare temporary water macroinvertebrate specialists that may not be as rare as we think according to Kieran Gething’s research. The scarce purple dun mayfly (Paraleptophlebia werneri; left) and the winterbourne stonefly (Nemoura lacustris; right). Source: Adapted from Fig. 1 in Macadam et al., 2021. pp. 28; Original photo credits are displayed in the image).

After lunch, Prof. Paul Wood delivered a passionate and sentimental memorial to Richard Chadd, who sadly passed away last year. Richard’s many years of work at the Environment Agency included delivering pioneering research that informed better management of freshwater ecosystems, not least temporary rivers and streams. His legacy will continue to inspire and guide scientists and practitioners working on sustainably and effectively promoting the health of freshwater ecosystems.

The late Richard Chadd who sadly passed away last year. Richard’s many years of work at the Environment Agency included delivering pioneering research that informed the better management of freshwater ecosystems, not least temporary rivers and streams. Photo credit: Freshwater Biological Association.

The final session of the day chaired by the Environment Agency’s Tim Sykes included presentations on how local communities and stakeholders can be involved in the management of temporary rivers and streams. Tim kicked off the session by discussing societal perceptions of English winterbournes, with such environments often being undervalued due to their physical modifications, as well as their association with severe drought and fish kills. While the dry phase has negative societal connotations, Tim did note that the return of flows brings optimism and excitement to some local communities. Mike Bogan, of the University of Arizona, then discussed his involvement in a project returning flows to an artificially dry river, and detailed how biota and societies responded. In particular, he documented the unprecedented recovery of odonate (dragonfly and damselfly) communities, with 7 species colonising within hours of flow restoration and 42 species returning within 7–8 months. He went on to discuss complications associated with such a large project comprising a suite of stakeholders and landowners. Alex Deacon from Wessex River Trust gave the final presentation of the day by discussing the organisation’s work engaging with local communities on their work on temporary rivers. He highlighted how farmers have become more keen to investigate temporary river management solutions through promoting gains in natural capital.

Photographs from the first day of flow resumption along the Santa Cruz River, Arizona, USA, with various odonate (dragonfly and damselfly) species returning within hours. Source: Adapted from Fig. 2 in Bogan et al (2020).

The day concluded with a group discussion which broadly comprised two topics. The first of which focussed on a need to plug data gaps (e.g., hydrological and ecological monitoring) in temporary rivers and streams. Specifically, building on earlier talks of mapping temporary watercourses to understand their distribution across the landscape, various contributors highlighted a need to use tools such as groundwater models to help support and validate such efforts. The second topic focussed on how we as a scientific community can better involve and enthuse the general public and different societal groups on temporary rivers and streams.

References

Bogan, M.T., Eppehimer, D., Hamdhani, H. and Hollien, K. (2020). If you build it, they will come: rapid colonization by dragonflies in a new effluent-dependent river reach. PeerJ, 8, p.e9856.

Macadam, C., Stubbington, R., & Wallace, I. (2021). The specialist insects that rely on the wet-dry habitats of temporary streams. Freshwater Biological Association News, 81, pp. 28– 33. Available online via <http://irep.ntu.ac.uk/id/eprint/44944/1/1498769_Stubbington.pdf> [Accessed 22/6/2022].

Messager, M.L., Lehner, B., Cockburn, C., Lamouroux, N., Pella, H., Snelder, T., Tockner, K., Trautmann, T., Watt, C. and Datry, T (2021). Global prevalence of non-perennial rivers and streams. Nature, 594(7863), pp.391-397.